Prospecting for Minerals: A Practical Handbook for Prospectors, Explorers ...

Samuel Herbert Cox · 1906 · Historical

Fabi I.— lead, with SectlDDi on Smelting and DeillTerlHtlon, and on the ABiay and Analyile ol the Material! involved. Ulmtratlan). Luge Svu.

This 1906 document, Prospecting for Minerals: A Practical Handbook for Prospectors, Explorers ..., is preserved in the Mountain Man Mining Library for research and reference. Original source: archive.org.

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Prospecting For Minerals.

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The "New Land" Series Of Practical Handbooks.

Edited by GRENVILLE A. J. COLE, M.R.I.A., F.G.S.,

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Prospecting For Minerals:

A Practical Handbook

For Prospectors, Explorers, Settlers, And All

Interested In The Opening-Dp And

Development Of New Lands.

S. Herbert Oy.,

VMtb Slluetiatfone. FOURTH EDITION, REVISED.

London:

Charles Griffin &amp; Company, Limited;

Exeter Street, Strand.

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Publishers&#x27; Note To The Fourth Edition.

The Author has gone carefully through the book and made Buch corrections and alterations as the short interval between the editions made necessary, and it is hoped that the book will continue in favour aa hitherto

Preface To Third Edition.

It has not been deemed advisable to make any material alterations in the plan and scope of this work, so that, beyond careful revision and the addition of a few characteristic illustrations of important mineral deposits, the present edition is in much the same form as the previous ones.

The criticisms of the press generally, and the kind expressions of personal approval of the book which the Author has received from numerous practical men, lead him to hope that he has succeeded in his endeavour to produce a handy and useful book for prospectors in all lands, so far as all the important minerals and ores, their recognition and their modes of occurrence, are concerned. S. HERBERT COX. London, January, 1903.

Preface To First Edition.

The object of this volume is to give a sketch of those subjects which underlie the calling of the Prospector, without encroaching to any great extent upon the provinces occupied bj the sciences of Uineralogy'And Geology, or the arte of Mining and Metallurgy, which are too far reaching to allow of more than the briefest mention in a work of this sort.

It is evident, therefore, that the scope of the work must he necesBarily limited, but it is hoped that to the practical Prospector it may give certain hints as regards the recognition of Minerals with which he is unacquainted, while, to the student, it may afford an introduction to the subject which will be of use in directing his work into the proper channels.

S. H. C.

Lohikik,

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Contents.

Chapter I.

iHTRODUOIIOtr AKD HlNTS OS QBOI-OOT.

Introdnetion — Oeolooio*! Age — Oeneral Observationa — Mineral Deposita — AUuTUJ Deposit! — Conditiona which have to be tadied — Bocks — Ijiiieoui or Eruptive Rocke — Hjrdcothermal Rocki—TrappeuiRocka— Table of Eruptive Rooki — Voloaiiic Bocka — Sedimentaiy Bocka — Movements of the Rooka — Geological Obeervationa in the Field, 1-13

Chapter Ii.

Thb Deteshihation or Minebals,

Btraotore — ClaaTaRe — Luatce —Colour — H ardneM — Streak — Table boring Colour and Streaks of Metallic Minerala — Flexibility aDdSlaaticity— Malleability— Smell— Taate—SpecificOravitj' — Blowpipe Cbaracten — Determination of Minerals, 14-47

Chapter Iii.

Soluble Salta — Earthy Carboaatea and Sulphates, with Apatite, Fluor , and ColiteQuarts and Opal — Silicatfla of Magneaia and their Ciyatallographio Alliea — Anhydroua Silicatea of Lime and Alumina, with their Ciyatallographic Allies -Hydrous Silioatea of Lime and Almnina, with their Allies— NoD-oryetalline Silicate of Altmina,

nu OOHTBNTS.

Chapter Iv.

Pbxciods Stohbs A.ItD Gbiu,

Diamond— ConiD dam — Top&z— Emerald uid Beiyl — — Dichroite or Cordierlte — Tonnnaline — QamM — Rock

— Smoky Quarti or Cairngorm— Citrine Quartz or falls Topu — AmetbyBt Quarti — Chalcedony — Agate — Onyx— Sardonyx — Camelian — Chryoprae — Plasma — Heliotrope or Bloodtone — Ca t'e Eye — Opal — Orthoclaae — Oligoelaie — Labrodorite — Olivine or Chrysolite — Epidote — Kyanite— Veauviaiiite — Andaluaite- Turqnoiae- Ultratnarine or Lapia Lamli — Bocit— Colours ot Precious Stonea— Scale of Eardnenvf Preeiotu Stonn— Specific Graii of Gemi,

Chapter V.

STftATiriBD Deposits.

Chapter Vi.

MinERAL Vbinh abd Lodes.

Chapter Vii.

ClMflificatioQ— Impregnations— Eeticula ted Lenticular Aggregations— Irregular Masses— Flats— Contact Deposita— Cave Deposits, 105-114

C01Itent8.

CHAPTEE Vin.

CHAPTER IX Allotiaii DEPOsira.

feoroe of MatrUla — of Psreat Rfi— AnstrttUui Eeefe — Deep Leide— Hew island Reeb and Depotiti — Allnrial Dapoiita of BritUb Colnmbu— Value of Allafial Depoiito, . 129-133

CHAPTER X. NoBbi Mbtals.

OOIiD — PlTINUH — OSUIITH — IRIDIUM — TlLLVRTm.

— Uode of Deteotion— feroiu BalU— Qold in Br .

tmTeiDng Sedimentary Rooka — Beefa ai. . —ShooU— Saddle Reefs— Flat VeiDa— Gold in Itacolmnite— Qold (d Timadte— Gold in TFansrlTanla—aold In Nersda— Breooia Lodes — Qold iu Deep Leada — Platinum and Allied Metalfl— Tellnriam Minerala, 13S-14S

Chapter Xi.

Natire Silver — Argentite— Stromeyerine— Stephanito — Pyrargyrite and ProiuUte— Eerarjrite— Bromargyrite — lodaiyrite — Valniiig Silver Orel— OtJeu— Carbonate of Lead— Lead- Antimony Ores— 'Bonraonite — Lead Lodes — Shoots, . 1'

Oontbrtb.

Chapter Xii.

i Mbxoubt.

Chapter Xiil

General Charaoten of Copper Ores — ClMU1cation of Copper Ore* — Native Copper — Copper Orel — Tests lor Copper Ore— Copper Ore Depoaite, 102-171

Chapter Xiv.

TlH— TtTANIUM— TOKOSTEK— MOLTBDnj||.

Ceeaiterite— Tete for Caasiterite— Casaiterite Depoaite — Titamtun — Rotile — Octabedrite — Brookite— Wolfmin — Scheelite — Holjrbdenite, 171-lTS

Chapter Xv:

Ziho—Ibor—Nickbl— Cobalt— M anoanes b— Cbbohidh— Uiutn dm.

Zinc — Test* — Table of Zine Orea-Iron — Hnmatite — (Icethite and limonite— Magnetite— Siderite— Titanic Iron — Virianite— Sulphate of Iron— Iron Pyritee-Miipickel-Nickel uid Cobalt — Blowpipe Teata—Manganete Dree— Ctuominm—UraDinm, 179 192

Chapter Xvl

Snlpliur— Orpimeot— Realgar- Antimony Ora — Bismnth, ,

Ohapter Xvil

DumoDd — OoaJi — Petroleum— E Uterita— Ambsr,

CHAPTER XVnl. Qbnisil Hints aioABsma PRoarioniro, , . 204-213

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Pkospectin&amp; For Minerals.

Iktbddootion And Hints On

Mbtals aad MineraU occur in Nature with auch varying forms, and distributed under such different conditions, that it is inipossible to enunciate laws regarding their mode of occurrence, without giving so many exceptions that the value of the laws might be called in question. On the other hand, the minerabi themselves are easily recognised when found, if ordinary*Sntielligence is brought to bear in testing them.

Certain metals and minerals, such aa gold and the various ores of copper, which can be recognised readily without any special teste being applied, attract a large amount of attention &om prospectors who have not had any scientific training ; whilst those minerals which require some skill to determine are, as a general rule, passed over by the same men.

Apart from the ease with which gold is recognised, its intrinaio value, the absence of fluctuations in the market price, aad the certainty that no difficulty will ever be cxperieiioed in disposing of it, no matter in what quantity it is found, give an attraction to mining for gold which is not shared by any other metal. But, although gold possesses all these advantages, it is quite as difGcult to determine whether some gold-bearing deposits con be worked to a profit as it is to decide a similar question regarding tin, lead, antimony, or zinc.

There are a number of scientific questions which bear directly or indirectly upon the occurrence of minerals, and it is found that certain minerals are generally associated with certain rocks ; but, while this is the case, there would be no work for the prospector if the presence or absence of ores could he deter-

2 FBOBPECrlKa FOB MIHBBALB,

mined hj an examination of the geological stnictare of a district.

There ia a glamour aboat a prospector's calling 'which induces manj to undertake the work in which comparatiTBly few succeed. The independent life, the change of scene, the chance of making diacoyeries day by day aud of becoming wealthy in a moment, lead many to prefer this to the work of more settled mining districts where good wages can be earned. The true prospector never leaves his adopted calling permanently ; if pursued by bad fortune until his resources have come to an end, he will migrate to a mining camp and work for wages for a time ; but, afi soon as occasion offers, he returns to the field and continues to search for the Eldorado that he always feels confident he will discover. ' There ia little that a book can teach sucli men regarding the search for gold, but it is possible that they may obtain hints which would induce them to abandon worthless nndertakings, and also learn to distinguish, roughly, minerals which are not of common occurrence, but are still of value.

For the student who ia preparing to embark on his career, some detailed information ia necessary, and some little time must be devoted to a general description of mineral deposits, their probable origin and modes of occurrence, before investigating the conditions which are peculiar to individual groups of ores.

It does not appear advisable to enter into the theoretical questions of geology, and in these pages it will be assumed that a general knowledge of the principles of that science has already been acquired ; there are, however, a few points which require to be emphasised.

QolQgioal Age. — From the prospector's point of view the geological age of the rooks is a matter of very little importance, and this cannot be too clearly understood. It is true that in certain countries there are deposits of mineral which are asso> ciated with rocks of special geological age ; as, for instance, the coals of the European coalfields with bs of the Carboniferous system ; but when other countries are visited it is found that, although seams of coal exist, they frequently belong to other geological periods ; and the rocks of the Carboniferous system are of an entirely difierent nature. Not to multiply instances, it may be mentioned that in New Zealand the Carboniferous rocks consist of indurated sandstones and slates, in which no traces of coal are found, whilst the coals themselves are of Cretaceous age and, in some cases, even younger.

INTRODUCTIOK ABD BISTS OflBOIiOGT. 3

Ab a further illastration, gold-bearing reefs are found tro- Teraing achistose rooka, diorites, ticc, in Weatern Auatralla ; in Lower Silurian strata in Victoria ; in Upper Silurian and Lower Devonian strata in New South Wales ; in Carboniferous and Upper DeTonian atrata in New Zealand, and in the same colony the auriferous reefa of the Thamea Goldfield intersect submarine volcanic rocks which are certainly not older than Oretaceous and may be little older than Miocene. It will thus be apparent that whatever other guidea may be of importance to the prospector, but little can be gained from a scientific knowledge of the geological age of the rocks. We have to go to each new diatrict with an open mind, and be prepared to find the conditiona prevailing different in many features from thoae to which we have beeu accustomed elaewhere. The nature of the deposits must be studied, pointa of resemblance to other localities noted, and differences investigated so that a true appreciation of the value of the mineral deposits can be formed.

General Obserrations. — It is not intended to convey the idea that experience gained in one locality will not be of any value in another; for there are many features which are the same wherever one may go, and, after investigating the mode of occurrence of mineral depoaita, a few of the more important of them will be enumerated for the guidance of students. It ia important to cultivate a general eye for country, and be able to determine from a casnal inspection whether any particular district presents features which render it possible that mineral deposits will be found ; and, at this point, a broad distinction must be drawn between those which are found in ntu, or associated with the rocks themselves, although under varying conditions, and which will be called in these pages "MinertJ Deposits"; and "Alluvial Deposits," which have been worn from their parent rooks, and re-arranged in the gravels or sands of rivers, on sea beaches, or in certain glacier drifts.

UineraL Deposits occur under a great variety of conditions, which will be dealt with later; but, so &r as their association with the containing rocks is concerned, the same remarks will apply to each.

It is seldom that the principal mountain range of a country is the more important repository of minerals, bat those ranges which fiank the main range often contain these deposits. It is quite possible that the reason of this ia that the rocks composing the principal ranges are harder, and less liable to disintegration and decomposition than those of which the flanking ranges are composed ; for the harder rocks, unleas interatratified with ihoae

/

FSOSPKOriNQ FOR MIHEBAL3.

of softer texture, are not so congenial to mineral depositB as those which are aubject to decompoBition when exposed to the atitao-l sphere. It appears, therefore, that, aa the harder rocks seldoW contain mineraJ deposits of importance, the higher ranges must, as a rule, be leas productive than those of leaser elevation. It must not be supposed, however, that the really soft rocks are those in which mineral deposits are most likely to be found ; for, unless a rock is indurated to some extent, it is hardly likely to contain mineral deposits of value ; it thus appears that rocks of medium hardness are generally the most promising, and that those which decompose readily, and form a considerable quantity of oxide of iron in the process, are, generally speaking, the more worthy of attention.

The physical condition of the rocks also requires to be studied. Whilst the actual angle of bedding, whether flat or steep, appears to exert veir little influence on the value of the deposits, it is seldom the case, where rocks have been subjected to much contortion, where, in fact, they are bent and twisted / into many sharp anticlinal and synclinal folds, that they con' tain mineral deposits of a permanent nature. v /

The intersection of sedimentary strata by igneous dykes may, generally, be looked upon as a favourable indication, more especially when these ai'e of a homblendic or augitic nature, such as diorite or diabase ; but this condition, like the last, must not be taken to apply where the strata are greatly disturbed by the intrusions. There are certain rocks, such OS limestones and serpentines, in which very irregular deposits of mineral occur, and which do not follow any known rules, and in rocks of this class valuable, though very erratic, deposits are occasionally found.

It will thus be observed that what one has chiefly to depend upon, in deciding whether a new district is worthy of the attention of the prospector, is a development of an "eye for country," which can only be acquired by practice, bearing in mind the hints given above.

Alluvial Deposits are those which are derived from the parent rooks by denudation, and thus the general remarks ' regarding the nature of the country will generally apply to these deposits as well ; but there are certain points relating to them which deserve special attention at this early stage of the subject.

Those alluvial deposits which occur near their parent rocks are governed absolutely by the conditions already quoted, but, seeing that the denudation which produced the sands and

IKTBODtroriON AND HINTS ON QSOLOOY. fi

gravels in which alluvial gold and other precious metals are lound hea operated during long periods ; that, in some instances, this denudation has been on a gigantic scale, while the amouub of gold included in the gravels formed is only small ; that BUbsequent cross-drainage may have concentrated this gold in tho beds of streams until it is in sufficient quantities to be or value, and that the gold may have been transported for great distances from the point from which it was originally broken ; it behoves the prospector to test any beds of gravel or other alluvial deposits he may £nd, by panning, in order to satisfy himself whether or no any metal or mineral of value occurs in them.

It is not only on tho surface, in the beds of streams, that alluvial deposits may exist, but they are frequently found buried at some depth below the surface soil ; in these cases shafts have to be sunk until the bed rock is reached, on which the metal is generally richer than in the overlying drift There are also numerous instances in which the contour of the country has been completely changed since the deposits were formed, and many cases might be cited in Australia in which old river beds, carrying both gold and tinstone, have been buried below sheets of basalt, necessitating heavy expenditure in testing the deposit before it can be decided whether the metal occurs in sufficient quantity to make it payable to work.

It must be obvious that very few surface indications of deposits of this sort can be looked for, and, although a prospector well acquainted with a district may be able to form conclusions, it is quite impossible for a new arrival to do so with any degree of certainty, without having recourse to a study of the work of previous observers on the structure of the country ; and here it is of importance to mention the fact that in every civilised part of the world a great deal of information, of a reliable nature, is available regaining the geological structure of the country, and the experience that has been gained as to the distribution of minerals. The res[]ective governments employ geologists, surveyors, and other officials to investigate these points, and to report concerning them ; and it is of the greatest assistance to any new arrival to procure these reports and study them carefully.

Condltiona which have to be Studied. — It must be borne in mind that the prospector has not only to find mineral which is in itself intrinsically valuable, but must also know enough regarding the methods of working, the costs of different processes, &c., to determine whether the metal or

6 Pbospectino Fob Hihebalb.

miDeral is present in sufficient qnantitj to make the deposit of value.

There are many considerations that vill affect a decision on this point ; for, in certain cases, deposits of very low value can be worked, whibt in others, even moderately rich ores are worthless because the conditions that prevail are not favourable. While it ia beyond the limits of a book of this sort to enter at all fully upon so important a subject, it will be well to indicate in some way the points which require special attention. Naturally, the first question is the richness of the ore ; a question -which can, in certain caseB, be answered approximately by an examination of it, by panning tests, or by assay of carefullytaken samples. In testing this question, it must always be borne in mind that the value of mineral deposits will vary irithin a distance of a few feet ; hence constant sampling should be undertaken at every point available, so aa to decide the extent and value of the richer and poorer portions of the deposit.

It 18 obvious that a deposit only becomes of value when sufficient ore has been shown to exist to make it certain that it will pay for extraction, and when it ia known what treat* ment may be necessary. Until that time the deposit is only a prospect, and, as such, comes within the province of the prospector.

Having tested a deposit in this manner and arrived at a knowledge of its intrinsic worth, other points require atten-

Is water power available to enable the mine to be worked at a minimum cost, and what expense is likely to be incurred in utilising this t

Do facilities exist for transmitting, by means of electricity, power generated by water at a point some distance from the deposits

Is there sufficient water available for the mechanical or metallurgical operations that will have to be carried on !

Is there much or little water in the mine which will have to be pumped 1

Is fuel available in large quantity snd at a reasonable cost J

Is labour good, plentiful, and cheap I

Can mining timber be procured cheaply and of good quality}

Is there a good and suitable site on which machinery can be erected t

What facilities of communication by rail or road exist, and what is the cost of freight !

hull, .. A''."->'ll-'

IKTBODUOTIDir ASD HINTB OIT QBOLOGT. 7

Is the ore of a refractory nature, or can it be easily treated for the recovery of the metal it contains i

Do special facilities eJuat which make mining very cheap I

It is upon the answers to these questions that the value of a deposit will depend, seeing that, in some cases, mines are worked and mineral extracted with large profits from ores which are not intrinsically worth more than lOs. or 12s. per ton; while, in other cases, ores that have a value of £i or £5 per ton, or even more, will not pay to work, because the oonditions are not favourable.

It must be clearly understood that only very large deposits can be worked which are of so low a grade as those first mentioned, because it is only by treating large quantities that the cost of extraction can he brought to a minimum, and an operation of this sort will involve a very large expenditure of capital at the outlet. It is difficult to further define the conditions which must be fulfilled, so that the prospector must rely upon his own judgment to a very great extent, bearing in mind the points already alluded to.

Books. — In the mineralogical portion of this book allusion will be made to the rook-forming minerals, and it is now proposed to give some account of the combinations of minerals which compose the different rocks, as well as the physical conditions ander which they occur.

Bocks may be divided into two great groups, viz. : — Those which are of eraptive origin, or were, at the time of their formation, in a plastic state induced either by fusion or the influence of heat in the presence of moisture ; and those which are of sedimentary origin and have been deposited by the agency of water under conditions very similar to those which now prevail upon the earth's surface.

The latter group, however, is capable of further subdivision into meohanioally and oianioally formed rocks; while the former may be subdivided according as they were formed at great depths below the surface of the ground, like the granites ; were intruded as dykes, like the Cornish elvans ; or poured forth from volcanoes, like the basalts.

These subdivisions, both in the eruptive and stratified rocks, are not clear and well defined, but merge one into the other. Granites and basalts, for instance, both occur as dykes ; whilst calcareous sandstones are formed partly mechanically and putly by organic means. It is not proposM to give any long description of the operations of Ifature in producing these rocks,

PROaPKCTIVO FOR MIN1BAL8.

3 for distinguishing the dlfierent

iit.

lOKEOUB OK EbUPTITE ROCKB.

IgneouB rocks are either of hydro tier ma!, trappean, or volcanic origin, and any classification should at the outset take this division into consideration.

The hydrothermal rocks include all those of granitic character, auch as granite and syenite, and their various modifications, which are characterised by the presence or absence of special minerals. It will be sufficient here to mention that Qronite is a crystalline granular admixture of the minerals, orthoclase, mica, and quartz ; and that Syenite consists of orthoclase and hornblende. There are a number of intermediate rocks, some of which will be found in the table on p. 9 ; but the limits of this book will not permit of details.

These rocks have apparently been formed at great depths below the surface of the earth, and in the presence of water raised to a considerable temperature, thus allowing the respective minerals to crystallise more or less perfectly from the magma formed.

By the term magma, it is implied that at depths below the Buriace the rocks existing, whatever their origin may have been, are raised to such a temperature that, were they on the surface, they would fuse ; but being under the pressure of the overlying strata they are unable to expand, and so fusion is prevented. But in the presence of water, which appears to occur to every depth it has yet been possible to explore, the heat probably effects a partial solution, and in the digester thus existing, a more or less pasty mass is formed, from which the minerahi crystallise in a consecutive order.

The fact that of the minerals which constitute granite, the felspar and mica, both more fusible than quartz, occur as crystals ; whilst the quartz forms a crystalline paste, which ia always moulded around them, is in itself a proof that the rock could not have solidified from a state of mere fusion ; moreover, the enclosure of a number of microscopic particles of water in the quartz of granite appears to indicate that, in some cases at any rate, water must have been present at the time of its formation.

The trappean rooka, as they were called by the older geologists, form a convenient field-group of rocks of medium crystalline grain, occurring in dykes and sheets. Moat dolerites and diabases come under this head

D,g,l,..cbyGOOglC

Introduction Asd Hints On Oeoloot.

!

la

if , 11 It

Si fl

Tltreoiu

XXX i : i

QUMi,!.

: i 1 : i

M i M

ADglt..

i ! Ixxx

!xxx I

! i i i i

X X i i :

XX s: i

XX 1 i 1 1 1 i i i i 1

s

Quartz porphyry (Elvan, *c.). Fine grained syenite, . Fine grained diorite, .

Diabaae,

Trappean

termediata

Voloanio.

Toloanlo rooka are those which have re&ched the surface, either through volcanoes or simple fissures, and have been distributed as lava streams or as volcanic dust, &o. ; thej have very marked differences in structure, dependent upon, their chemical composition. The traohytes contain a large proportion of silica, and are generally of a grey colour j they consist of hornblende and sanidine, which is a transparent variety of orthoclase. It must be remembered that in true trachytes nojree quartz occurs, and that when quartz cryatala are developed, or when there ia an excess of silica in the glassy ground, the rock becomes a rtayolite. On the other hand, there is a series of basic volcanic rocks in which the percentage of silica is not high, and these are known collectively as basalts. Basalt consists of augite and magnetite, with a certain quantity of one of the triclinio felspars, and, generally, olivine ; these rocks are named basalt, anamesite, or dolerite, according as they are fine grained, of medium, or distinctly crystalline structure. There ia also a series of intermediate rocks between trachytes and basalts, known as andesltes, in which the homblende-andesites consist of hornblende and a triclinic felspar, and are allied to the diorites ; whilst the augite-andesites are very closely allied to the basidts, but contain more silica in their composition.

Sedimentary Rocks.

The meohanioally formed sedimentary rocks consist of mnd, clay, sand, and gravel, together with their corresponding shales, slates, sandstones, and conglomerates, which have been produced by consolidation of the sediments. They are also at times changed, by a process of metamorphism, analogous to what takes place in the formation of granite, to schists, gneiss, or quartzite.

The organically formed rocks comprise limestones and coals, the former being produced by the accumulation of the shells of moUnscs, &c., which have extracted lime from the water to form their covering; the latter, by the growth, decay, and submergence of trees and plants. Besides these, certain beds, such as gypsum and rock salt, have been precipitated from solution in inland waters, such as the Dead Sea, or Great Salt Lake of Utah.

MoTsments of the Books. — These varied rocks which have either, as the sedimentary deposits, been formed under water, or, as the eruptive rocks, Intruded through other beds at all times during the geological history of the Earth, have, since their

IBTBODUCriOIT AHD BINTB ON OBOLOQT. 11

formation, been sabjected to numerous changes. Some have been raised from the sea without being tilted to any extent from their original horizontal position ; others have been folded into most fantastic shapes ; and others again have been completely inverted. In other cases, movements which have taken place since the rooks became solidified have caused fractures, and by the rocka on one side of the crack sliding on those on the other, fooltB have been produced.

Without entering into any of the theories which have been propounded to account for these tnovemente, it may be stated that, even at the present day, great and important movements of the land are continually taking place ; in some parts the land is slowly rising from the sea ; in others, a continued but gradual subsidence is going on. Earthquakes, moreover, produce slight oscillations of the land, and thus a redistribution of the land and sea is in constant progress

There is ample evidence, in the occurrence of fossiliferons locka which enter into the structure of important mountain ranges, that these oscillatiouu of the land have also occurred in the past, and the varying angles at which the different sedimentary rooks are lying show that in many cases they must have been sabjeoted to a lateral pressure, which haa produced the crumpling of the rocks already referred to, and, in some cases, the dislocations or foults which have also been mentioned.

Where the rocks have been folded in the form of an arch, they are said to form an antiolinal ; and where they occupy a basin, they are spoken of as forming a BynolinaL Widespread folds of uie foregoing nature are called ge-antiolinals and geo-synolinals respectively ; and it is interesting to note that in the areas occupied by ge-antidinals the rocks are generally so much broken and jointed that they offer great facilities for removal by the ordinary denuding agents ; hence it is hardly to be wondered at that ge-anticlinals generally occupy valleys and depressions on the present surface of the earth. Not only is this the case with large structural movements, but the ordinary anticlines and synclines, which are of more local character, are found to exhibit the same peculiarity ; for the synclines generally constitute the hills, while the anticlines occupy the valleys.

Obaerrations in the Field. — While it is not necessary for the prospector to make accurate geological surveys of the country on which he is engaged, it is very often of importance for him to obtain some idea of its stmoture ; as upon

PROSPBOItNO TOR HINRRALS.

this may frequently depend the value, or otherwise, of special areas to which he iaa.j be inclined to devote his attention. More especially in stratified deposits, such as coal, is this of importance ; but, even when dealing with lodea, it is frequently useful to study the distribution of the rocks in order bo discover what effect those of different nature exert upon the mineral deposits.

In examining the surface of a country in which the rocks are of sedimentary origin, it will be found, as a rule, that the beds are inclined at varying angles to the horizon, and in making a geological survey of any special district it is necessary to note the dip and strike of the rocks at every available point When any well-marked bed occurs, such, for instance, as a seam of

Fig. 1.— Plan.

coal or belt of conglomerate or limestone, its line of outcrop should be carefully followed and mapped ; the boundaries of any eruptive rocks should also be clearly delineated on the plan.

The atrike of a rock is the direction of a horizontal line in any of the beds ; or, in other words, the direction in which a level drive would be put in on the Soor of the bed. The dip is a line at right angles to the strike on the plane of the beds, and the angle is to be measured in relation to the borizoO.

When any particular bed is followed on the surface, it is often found that it does not continue with the same strike for any great distance ; that, in fact, it gradually veers round, as shown at (a) in the sketch, the direction of the dip changing at the same time. By a study of a plan thus made the positions of the anticlines and synclines can be determined, and other lines of elevation can also be notwl ; and a section constructed,

such as the foUoving, which Herves to convey a very fairly accurate conception of the structure of ths country. As a. natter of &ct, the boundaries of rocks are sometimes rather obscure in consequence of the variable movements which have occurred ; but the occurrence of faults and dykes is what makes this tracing of boundaries on the surface most difficult, Tba

Fig. 2. —Section.

displacements due to faults may be only an inch or ao, or may be several hundred feet ; while in a few exceptional cases, as, for instance, in the fa,alt which crosses Scotland from Dunbar to. the Ayrshire coast, the displacement may be as much as two or even Uiree miles.

A study of faults is of very great importance, more especially on account of their close association with mineral lodes ; but . faults should never be assumed for the purpose of explaining difficulties which are encountered in mapping the sur&ce geology, unless very good evidence of their existence can be found, and until every other means of explanation of the phenomena has. been tried and found wanting.

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Chapter U.

TBR DETBBKIlIATIOIl OF IIIHEKALB.

Tbz determination, of the more important mineralB which majr be met with deserves special attention at the outset of the subject, and the present chapter will be devoted to the aitapler means of distinguishing them. It is not, however, intended to enoroaofa upon the detailed study of mineralogy, on which subject the many valuable treatises published can be consulted.

When minerals occur in a sufficiently pure state, thay are generally cryatalliaed more or less perfectly, in certain definite forms — e.g., ptfritee, caieite, and garnet — but many minerals, especially those forming sedimentary rocks, are composed of very minute grains, in which either the oryHtolline form baa been imperfectly developed or tbe minerals are altogether amorphous— e.., earthy Umettone, cocU, and massive pyriUs. A. few are incapable of crystallisation — e.g., amber and limonite.

Mineralogy treats only of natural inorganic substances which have tbe same composition throughout ; but rocks, which may be composed of several minerals, either crystallised or not, sometimes exhibit on a large scale regular forms, which must not be considered as due to crystallisation, but to the process of -cooling ; or to cooling and drying, and the consequent contraction. Compact basalt, for instance, which has been formed in .a molten state, is frequently divided daring cooling into more -or less regular prisms, are often six sided; and some of the extensive beds of gypsum near Paris have, in drying, assumed the form of huge prismatic pillars.

There are certain physical properties of minerals which are of importance in their determination, regarding which a few notes will be of interest.

SrRucrruBR, When minerals do not occur either in isolated crystals or in .distinct groups, but consist of aggregated crystalline or compact articles, they affect different kinds of structure ; and this struo-

THE DETERUIITATIOH OP XtNEBALS. 15

ture, besides assisting in the determlnatioa of minerals, is of economic importance; for on it depends the value of certain minerals for ornamental purposes.

Oran'olar Stnioture, of which stuidstone may be taken as a type, is produced by more or less rounded grains being cemented together, A coarse granular structure is best seen in chrome iron-ore, in which the grains, since they are not cleavable, can be noticed at once. Galena and zinc blende are often more or less granular; but, since both these minerals cleave readily, the fractare is lamellar when the grain of the ore is coarse. If, however, they are fine grained, these, in common with many other ores — e.g., copper glance, cinnabar, pyrrhotine, and, more rarely, ewvrgiu and stibniU — exhibit a fiiie granular structure, and are sometimes so fine grained as to approach more or less perfectly to a compact texture.

SaoohBfold Stractare. — When the mineral is composed of small crystalline grains, showing facets and cleavages, the Btruoture is called saoobaroid — e.g., aUUuary marble and alabaater,

IfEimellar Stfuoture. — When the crystalline particles are minute and flat, being laid one on the other, the structure is termed BOaJy — e.g., chloriU; while a true lameUar or 1n.TniTm,T foliated structure, which is best seen in tola and mica, also exists in molybdenile, and more rarely, and in a less perfect manner, in mc/cel glance.

Capillary struotuxe is best illustrated by aaheatoa, the fibres of which are readily separable; but a similar structure may be noticed in some specimens of milisrite, the fibres being easily separable, but small, brittle, and generally radiating. Only a few other mincrala possessing this structure could be mentioned, and an equally small number occur in velvet or tuft-like excrescences.

Fibrous Btraotore is the term employed to describe those minerals in which the fibres cannot be easily separated, and is generally to be observed in minerals crystellised in a lode perpendicular to the walls of the fissure ; but is sometimes developed parallel to the walla, or even in radiating groups. In the first two cases the fibres are straight, as in ehrgsotile, which forms small veins in serpentine, and is only a variety of serpentine itself; and again, in caleile and gypnan, two minerals which sometimes exhibit this structure, but do not ordinarily possess it; both fibrous calcite and fibrous gypsum have been called mtin-jpor, and are cut as ornaments. The fibrous radiate tmctare is conspicuous in malachite, wood tin, and some

heBmatite$; U well marked in stnlttctiteB of ealeite, ban/tet, and caiamine, 'while gothiie, fpheronderite, and apatite may atso be mentioned as occurring in radiating fibrous forms. Minerals possessing this radiate structure are often called " conoretions," but many concretions consist of concentric layers where there is no sign of crystallisation, and must, therefore, be distinguished from those in which crystallisation exists.

Badiate Struotore is not only found in minerals formed of minute needle-shaped crystals, but stout prismatic crystals with pyramidal ends are sometimes arranged in radiating groups, as in the case of amethyst quarts when crystallised in vughs or cavities in rocks or lodes. Pyrilei also, and azurite, when found in balls which have crystallised iu a semi-liquid mud, exhibit the above structure. When radiating crystals assume a slender prismatic form they diverge from one another, sending their needle-shaped projections in every direction around the centre, like spines on a sea urchin ; pyrolueile, ttUmile, and natrolite occur in such forms.

Baoillary Struotiire is the term used to describe those mioerala which occur grouped in bundles like sticks — e.g.,Epidote.

Dendritio Structure. — Where many crystals are attached one to the other, like beads in a necklace, and especially where these diverge like the branchea of a tree, they are called dendritio. Native cojiper, silver, and gold frequently occur in this form, and oxides of Iron and mangaaese are often found in the joints of rocks crystallised in the most beautiful fem-Iike

ConOTetionsry Stmotnre is affected by uncrystallised mineral* which have grown from a centre in concentric layers ; and may also be seen in certain rocks — e.g., basalts, BandtUmee, &o., in which decomposition has taken place around centrea Where nodules have grown around a centre in mud or loose sand, the form is spherical or nearly so. Many valuable ores of iron occur in spherical forms ; exteuBive deposits (oolitic iron) formed entirely of small grains occur in the Jurassic system of Europe ; pisolitic ores, in which the grains are the size of a pea, are found in the Tertiary rocks, and similar ores also occur in serpentine. In the Jurassic system, oolitic limestones composed of small perfectly round grains of carbonate of lime occur, and a simitar structureis devoted in the calcareous sand on the shores of the Great Salt Lake at Utah.

The centre of these nodules is sometimes formed of a mineralgrain, and very often of a fossil plant, fish, or shell. In slaty rocks the nodules are flattened and irregular in shape, and ara sometimes mistaken for fossils.

THE DBTBBMINATIOH OF IflllXRALS. 17

Mammillary Straotiue. When conoretious have been formed at the same time ai-ound several centreB, which are at regular distances apart, a mammillory structure is induced — e.ff., chaieedony, which is very variable in fonn and size ; different modificationB are described as botryoidal (like a bunch of grapes), remform (kidney-like), &o.

Nodules of ironstone with fossil fish occur in the Carboniferous and Permian syatema of Europe, and nodules of oement stone in the Cretaceous rook of Kew Zealand. When depoaition takes place around a stick, the concretion haa the form of a cylinder, this structure being very common in some bog iron ores; and earthy cobalt ores are found under the same conditions in New Caledonia, where thej occur in a decomposed diorite associated with serpentine, and have accumulated around the roots of existing trees. Concretions of manganese ore are also formed in the depths of the sea.

VitreouB Structure. — When minerals exhibit no sign of crystallisation they are called amorphous ; and some which do not possess the power of crystallising can be distinguished as having a oompsot or vitreous structure — e.g., amber.

Cleavage.

Crystallised minerals have a tendency to split more readily in some directions than in others; this property is termed oleavage. In some minerals the deavagea are so eaay that, in transparent varieties, the planes of cleavage can be seen through the crystals, this being often the case in Iceland-spar, oTlhodoM, and baytet.

In the cube and rhombohedron, in which the faces are all of the aame shape, there are three directions of cleavage parallel to the sides — e.g., galena and rock-salt in the cube, and caidte, dolomite, and aiderite in the rhombohedron. These cleavages are very apparent and are good characters for recognition of these minerals

The most useful instance of cleavage is that which occurs in the diamond, in which there is an easy cleavage parallel to the sides of the octahedron ; advantage is taken of this property in shaping diamonds for outting. If the blade of a knife is applied in tne proper direction, a smart blow will effect the cleavage.

In six-sided prisms there is an easy cleavage parallel to the base in some minerals — e.ff., beryl or emerald and apatite.

In the rhombic prism there is also irequently an easy cleavage parallel to the base— e.j., topaz and tale. Barytea, which cryatallises

ia modified rhombic prisms, haa two easy cleavageH parallel to the aides of the prism, and one parallel to the basa

In the oblique prisma oforthoeleue there are two easy cleavages, one parallel to the base and another at right angles to the first and parallel to the oblique diagonal. They are at right angles to oae another, hence the name of the mineral

Cleavage is also a property of certain rocks — e.g., slain — and is moat perfectly developed in roofing slates of good quality. In quarrying aandatonea advantage is taken of the joints of the rock to divide it into building stones and slabs of different thickness, which have subsequently to be dressed on the sides as required; but these properties of jointing and cleavage in rocks are of quite different origin from the cleavage of minerals, being due entirely to stress or pressure in various directions after the consolidation of the rocks, and have no relation whatever to the composition of the rocks, whereoa, cleavte in minerals is a structural peculiarity, which is constant in certain mineral species.

Lustre,

The term lustre is employed by mineralogists to describe, with certain adjectives, the brilliancy or gloss of any substance. In describing the lustre, well-known substances are taken as the types, and such terms as adamantine lustre diamond-like) and Titreons lustre (glaasy) are used. When minerals do not possess any lustre at all they are described aa "dull." The lustre of a mineral ia quite independent of ita colour.

The terms usually employed to describe the luatre of minerals are as follows : —

3. Ad&mimtine. 7. Nacreooa.

These terms are purely arbitrary for, although a plate of polished silver may be taken as the best type of metallic lustre, this is also exhibited by all the metals irrespective of their colour, and by most metallic sulphides, such as pyrites, atihnite, &c.; hence no distinct line can fee drawn between those minerals possessing a metallic lustre and those coming under the sub-metallic group, of which diallage and anihraeiU may be taken as types. The luatre of minerals will frequently vary —

(o) As they are more or less impure.

(6) As other physical properties vary.

D,g,l,.9cbyGOOglC

The Deterhi Nation Of Uikebalb. 19

Id illustration of the first claas of variations, irindow glass may be taken as the type of vitreous lustre ; but glass can be made to exhibit a lustre approaching that of the diamond, mother of pearl, opal, ikc, by the admixture of certain chemical substances. Something approaching; an adamantine lustre oan be imparted to glass by lead, and the same effect can also be btained, although with greater intensity, by substituting the rare metal thallium, which is very closely allied to lead in its chemical properties. Very good imitations of the diamond are made in this way, which are sometimes difficult to detect by a superficial examination.

The second class of variations may be illustrated by gypsum, which has a vitreous lustre when crystallised, but a silky lustre when fibrous.

Many minerals possess a difierent lustre on diiferent faces ; pyrosjnalite, for instance, which crystallises in the form of a sixsided prism, has a semi-metallio lustre on the sides, while the -ends are greasy or nacreous.

Oalcite and gypsum are vitreous on some &cea, and nacreous on others ; and the same may be said of oeleatine, orpiment, and orthoclase.

The lustre of minerals may be taken advantage of for the first subdivision in a scheme for recognition ; and for this purpose it iaonly necessary to divide them into those which have a metallic lustre and those which no not possess this property.

Metallio and Semi-Metollio IiOBtre. — The first term needs no definition ; all metals in the native or pure state, and especially the noble metals, exhibit this quality in the highest degree, and are, indeed, so bright when polished that they can reflect images perfectly. Some sulphides have a perfect metallic lustre, and iron pyrites was formerly used by the Indians of South America to make their mirrors. All metallic sulphides have a metallic lustre, with the exception of zino blende and cinnabar, which are adamaatine ; although some black varieties of zinc blende containing much iron might be described as metallicadamantine ; and hauerite (sulphide of mangaaeee), which has but an imperfect metallio lustre.

Without HCetallio Iinstre.— This group inolndes a large number of minerals, many of which are of commercial value ; and it will be well at this point to call attention to those which possess an adamantine lustre. Of these, the diamond aSbrds the most perfect type of adamantine lustre, although other wellknown minerals can also be considered as good illustrations — t.g., catsiterile when in pure and shining crystals, eircon, and

20 Fkobpsctiitg For Uinerals.

eeruaaite. It may be well to agaia reiterate tlie fact that colour has nothing to do with this property of ]ustre.

Most minerals whose lustre is adamautine are yerjr heavy ; the diamond is lightest — ap. gr, 8*6 ; then oelahedrxte, blende, and gOthile — sp. gr. &bont 4. Between 4 and fi sp. gr. another variety of titanic acid called rutile and also sircon occur; between 6 and 6 Bp. gr. vaiarOinile, cuprite, embolite, pyrargyrite, and prouslite are found ; between 8 and 7 ap. gr. eroeoinie, eeruaeite, angletite, and umljeniu — all of which are lead minerals ; these and calomel, or chloride of mercury, have an adamantine lustre ; and between 7 and 8 ap. gr. may be noted cassiterile, or oxide of tin ; mimetite, and pyromorphite — both of which are lead minerals; wolfram, or the tungatate of iron and manganese, and cinnahar. A few of these — e.g., rutUe, pyrargyrita, and wolfram — have a metallic adamantine lustre.

Out of the twenty minerals mentioned above as possessing an adamantine lustre, the diamond is the only non-metallic mineral ; the remaining nineteen are metallic, and of these

The remarkable property possessed by lead of imparting an adamantine lustre to minerals and artificial products is well known, and is taken advantage of in the imitation of precious stones, but the greater the proportion of lead employed, the softer is the glass formed.

Coloor.

The colour of minerals may be due to four different causes ; but in some cases it is difficult to say to which of these groups coloured minerals belong.

Qbouf 1. — Those in which the colour of a mineral is that which it would possess when pure, or when artificially formed.

Gkodp 2. — Those in which the colour is due to the mixture of substances crystallising in the same form, and replacing one another in the composition of a mineral.

Gboof 3.— Those in which the colour is due to a small quantity of (Solouring matter, dissolved in a, mineral, by which its chemical composition is not greatly affected.

Group i.— Those in which the colour ia due to a mechanical mixture of substances, which are not dissolved in the mineral, but can easily be distinguished on microscopical examination.

THB DETXBHtyATION OF HISBBALS. 31

In this group are included those minerals whose colours are due

to mere impregnation.

Gbocp 1. — The first group can be illustrated by the following examples : —

Black. — Graphite, coal, and black oxide of copper.

Blue. — Azurite and lapis lazuli.

Q-reen. — Malachite, libethenite, dioptase, atacamite, nickel ochre, texasite, and bromargyrite.

Yellow, — Sulphur, amber, orpiment, and wulfenite.

Orange. — B ealgar.

Bed. — Cuprite, pyrargyrite, cinnabar, red ochre, and red htematite.

Fink, — Brythrine, diallogite, and rhodonite,

WUte or ColoorleBS. — Nearly all the alkaline and earthy minerala when pure— e.., barytes, gypsum, calcite, meerschaum, cryolite, and quartz.

It will he seen that nearly all coloured minerals of the first group are metailic, although none are included in the above list whose lustre is metallic; they are, with few exce])tion3, anhydrous oxides of the metals, metallic sulphides, antimonidea or arsenides.

A few minerals possess a metallic lustre and characteristic colour, as follows : —

Tlolet to Copper Bed or Tlolet Brown. — Erubescite or bornite.

Greenish Grey,— Tin pyrites.

BrasB Yellow.— Millerite and copper [>yrites.

Copper Bod.— Native copper.

Iiight Copper Bed. — Nickeline, breithauptite.

BeddiBh Silver Wliite. — Cobaltine.

Beddish Brown (due to tarnish ; normal colour on fraotore, tan white to steel grey}- — Domeykite.

YellowiBh Brown to Copper Bed. — Pyrrhotine.

Violet Brown. — Nickel pyrites, sternbergite.

Brown Black. — Hauerite.

Group 2. — The most common instances of colour due to the interchange of iaomorphous substances are those of the carbonates of iron (aiderite), of manganese {diallogite), of lime (caicile), and of magnesia and lime {dolomite). The two first are coloured, while the other two are colourless or white ; but, since they can replace one another in any proportion, ntUriU, which is yellowish,

aad diallogiU, of a floBhy colour, wiU impart a shade of colonr to ealeiie or dotomile when combined with bhem.

Kerargyrile and brcmuvrgyriU are also isomorphous ; the first is grey in colour, the second dark groen ; and mixtures of the two, or chlorobromides of siiTer termed emholiU, &c., are of all shades from grey to dark green, according to the relative proportions of chlorine or bromine they contain.

Group 3. — Very little seema to be known of those substances, a very small proportion of which at times impart bright colours to minerals. The colour so derived may be described as accidental, since the trace of colouring matter does not greatly affect the chemical composition of the mineral, and in this clasa may be included all the gems. Diamond, which is colourless when quite pure, is occasionally red or blue, and then attains a fabulous value ; but is more frequently yellowish, brown, or black. Corundum ifl commonly blue {sapphire), red (rwiy), more rarely yellow {oriental topaa), and still more rarely green (firiental emerald) or violet (oriental amethyst).

Topaz is colourless, yellow, or light blue. Emerald, beryl, and aqua marine are the same species, but the first is of a rich deep green and the others of a pale bluish-green colour. The colouring matter of the emerald is still uncertain, for, although some analysts are said to have found chromium present, the emerald loses its colour at a red heat, at which temperature oxide of chromium should not be destroyed; this seems to suggest an organic matter as the colouring agent.

Quartz, which in its pure state is colourless, often occurs milky, smoky, or black, more rarely yellowish (citrine quartz), imitating topaz or violet (amethyst). A crystallised variety from Spain is hyacinth red, and a compact variety pink.

Amongst minerals other than gems three are most remarkable on account of the different colours they assume, these are fluor-spar, apatite, and rock-salt Fluor-spar and apatite occur in nearly the same shades of colour, ranging from colourless to white, pink, red, yellow, green, blue, violet, and the intermediate hues. Rock-salt is found colourless, white, red, yellow, and blue.

A variety of orthoclase, remarkable for its apple-green colour, ia found in Siberia and Colorado. The colouring substance is still unsettled, although stated by some to be copper.

It is not always easy, or, indeed, possible, to draw a clear line between the coloured minerals of Groups 3 and 3. If the most notable groups of the silicates be taken — e.g., the hornblende, augite, game epidote,' and tourmaline groups — it ia found in

THE DETERUItTATlON Of HINBHALS. 33

each that, while all the mineralB compoiiuig the group obey the fwme laws of orystaUisation, and only vary in compoaition within certain limits, the minerala are white, colourless, or highly coloured, according to the proportion of colouring matter, chiefly oxides of iron, manganese, and chromium, present. In the hornblende group there are white, or nearly white, varieties and IremoHle), which do not contaiu iron ; an intermediate variety (actinolile), which contains a smaU quantity of iron, is green ; and a third variety which contaios a large proportion of iron, ia black, or nearly black.

In the augite group there ia a variety (diopaide) which is generally transparent, colourless, or pale green, and contains only traces of iron ; while two other varieties are nearly black, and contain large proportions of iron and manganese.

In the garnet group there ia a variety (groaaviaria) which is white or very pale green, and contains very little iron ; a red variety (almandine), used as a gem, and containing much iron ; a black variety (melanie), also containing much iron ; and a green variety {uwarowite), containing much chrominm.

In the tourmaline group Che substances which impart colour are more difficult to determine precisely. Those containing much iron are brown or black ; the green contains iron and manganese ; the red containe manganese and no iron ; and the colourless contains no iron, and only a trace of manganese. All the colourless and light-coloured red and green varieties also contain lithia.

Group 4. — The substance which most frequently colour* rooks and minerals mechanically is oxide of iron, imparting a browniah or red colour to earthy-looking minerals and rocka, and it ia to this also that the yellowish and reddish colours of some sandstonea and limestones, used for building purposes, is due; although, in some marbles, the colour is said to derived from organic matter.

The nickel ore of New Caledonia, which consists of sUica, magnesia, and oxide of nickel, seema to be, in some varietiea at least, only silicate of magnesia impregnated with oxide of nickeL In some mines the silicate of magnesia exists nearly or quite free from nickel, and of a pure white colour, whence it passes through all shades to the richest green. Some specimens under the microscope ahow the green oxide of nickel diaseminated in grains throu the white silicate of amnesia.

In some cobalt and nickel mines in Germany stalactites of carbonate of lime are coloured pink by a mechanical imprnation of arseniate of cobalt-

2i PBOaFXCTUffl roB kiiikkau.

The silicftteB kdcI carbonates of zinc are white when pore, the presence of iron eu a mixture often gives them a yellow eolonr ; and calamine, when bine, ia coloured by copper.

Habdnkss. The hardest labBtance known in nature ia the di&mond ; all other minorala can be scratched by it. Between this and the softest — .ff., tale and hoover — certain minenilB have been chosen to form a aeries called the koala of hardness, which is of great use in the determination ot mlnerala. It need hardly be added that the true hardness of a mineral is that which it exhibits when approximately pure, and is best tested in crystallised varieties.

Sou.! or HAttDNBS.

Flnoi- Scratohed b; iteel of ordinary hardnesi.

6. Orthoclaae— Scratclied by well tempered atoel— not

by window glaaa.

7. Qturtz. S. Topaz.

9. Comndnm. 10. Diamond.

In descriptive books of mineralogy the hardness of minerals is always expressed by numbers ; thus, chromiU H. 0-S, signifies that this miuera.) will scratch apatite, but can be scratched by orthoclase.

Some precautions are necessary when testing the hardness of any mineral. The scratch should be made on a smooth clear surface and with a sharp edge or angle of the scratching mineral. It often happens, if the mineml experimented upon is the harder, that, instead of a scratch, a line of dust is left on its surface. This should be carefully wiped away, when it will be easily seen that no scratch ha been produced on the harder mineral, and that the edge of the other has been blunted. This is what would happen if an attempt were made to scratch topas with quartz or corundum with topaz.

Streak.

In testing the hardness of minerals another character of importance — viz., the streak or colour of the dust iormed when a mineral is either scratched or powdered, may be observed.

THB DETIBHIITATIOir OF HINXRAU.

!

Jl

a

1 j il ...;..; .

n

..ir i 1 . . . 11 . . .

h

a fc

26 PBOSPECTINO rOR UINERALa. y

A few minerala which are malleable — e.g., copper glance and tilver glance — aa well as the malleable metala ttemselvea, instead of giving a dust when scratched afford a shining streak. The streak, however, of moat minerals ia of a lighter colour than the mineral itself

A certain number of minerals with metallic or semi-metallic lustre are difficult to distinguish by their mere appearance, their colour ranging from silver-white to iron-black. For a discrimi&Rtion of these their streak is frequently of value, and the preceding table will be of service in distinguishing them.

Regarding these it may be noted that stibnite frequently has a blackish tarnish, bisTauthine and domeykiU have a yellowish iridescent, trnaltine has sometimes a greyish iridescent tarnish, while gersdorfftte and occasionally galena are tarnished grey or greyish black. Polybasite in small crystals is red by transmitted light and the dust of enargite has a metallic lustre. Among the softest minerala a few are malleable like was — e.g., ozokerite and korn-silver ; whilst others are composed of particles or lamellse so slightly cohesive that they separate when either touched or rubbed, and soil the fingers more or less readily — e.g., molybdenite, earthy manganese, red and yellow ochres, steatite, graphite, &c.

Flexibility and Elasticity. Some minerals can be easily bent without breaking — e.g., tala, miea, chlorite, molybdenite, riative silver, &c. Those that, after being bent, can resume their former shape like a steel spring are called elastic— e.g., miea, and elalerite. A remarkable instance of flexibility, even combined with elasticity, amongat the rocks ia that of a micaceous sandstone from Brazil called itacdumils, which ia the matrix of the diamonds there.

Malleability.

Malleable substances can be hammered oat without breaking,

and it is on this quality that the value of certain metals in the

depends — e.g., copper, silver, gold, lead, iron, Ac

A few are malleable and at the same time sectile, that ia to

say, can be cut with a knife — e.g., silver glance, ham-silver,

and ozokerite.

Mineral caoutchouc (elalerite) is sectile, but, like India rubber,

oan only be shaped when hot. The elasticity of elaterite is so

characteristic that the mineral wiil be readily recognised.

DuctiUty or the capability of being drawn into wire ia a

property which is confined exclusively to certain metals. It is

Thb Drtebu I Nation Of Uinrbalb. 27

posBflSBed by gold in the highest degree, slace that metal can be drawn into the finest wire or rolled into leaves of aach fineDes that 30,000 of them are not thicker than an eighth of an inch.

Shell.

A few minerals only, like bitumen, have a strong smell, which is readily recognised ; but specimens generally require to be struck with a hammer, rubbed or breathed upon, before any smell can be observed. Some black limeatonea have a bituminous odour, while some have a sulphurous, and others a fetid Bmell; hydraulic limestone haa a smell of clay, which can be detected when the mineral is breathed on. Some minerals containing much arsenic — e.g., mispiehel — smell of garlic when struck with a hammer.

Taste.

Only soluble minerals have any taste, and this oan only be described by comparison with well-known substances — e.g., acid, vitriol; pungent, sal-ammoniac; salt, rock-salt; cooling, nitre; astringent, alum metallio astringent, sulphate of copper ; bitter, sulphate of magnesia ; sweet, borax.

Sfbcifio Gravity.

Prospectors soon acquire some profioienay in testing the weight of minerals by handling them, and a little practice with wellknown snbstukces will enable them to class most minerals within certain broad limits by this system of observation. The specific gravity of a mineral is its weight compared with water at standard temperature and pressure, which is taken as the standard, and described as having a specific gravity of 1 ; consequently, to determine that of a mineral it is necessary find the weight of a piece of the mineral and that of a corresponding bulk of water, and to divide the first by the last.

This can be done with great accuracy in the laboratory, where delicate balances are available, but is not applicable in the field, when the most that can be undertaken is to class minerals roughly within certain broad limits, and, indeed, this is frequently sufficient for the prospector. A rough classification of minerals under three groups is as follows, the arrangement being consecutive ftm the lightest to the heaviest. This list does not include

all the minerals mentioned in this book, but may be t&keti aa a Bcale which will serve for purposes of comparison with other mineralfl : —

Oroup 1. — Specific Gravit; leaa than 3'6. — Amber, bitumen, lignite, coal, natron, sal-ammoniac, borax, Epsom salt, anthracite, potash alum, copperas, saltpetre, sulphate of zinc, sulphur, nitrate of soda, chabazite, graphite, sulphate of copper, rock salt, opal, gypsum, harmotome, quartz, orthoclase, lapia lazuli, serpentine, beryl, emerald, vivianite, cordierite, albite, anorfchite, labradorite, alunite, talc, steatite, calcite and marble, cryolite, dolomite, magnesite, aragonite, mica, fluor-spar, tourmaline, turquoise, anhydrite, nephrite {jade), apatite, andalusite, calamine, epidote, hornblende, augite.

Group 2. — Speoiflo Q-raTity between 3*6 and 8'6. — Topaz, diamond, olivine, diallogite, realgar and orpiment, spinel, pleonaste, strontianite, chrysoberyl, rhodonite, azurite, spathic iron, limonite, blende, celeatine, garnet, gosthite, corundum, malachite, copperpyrites, pailomelane, brookite, rutile, willemite, amithaonite, witherite, manganite, tnnantite, chromite, tin pyrites, molybdenite, magnetic pyrites, barytes, atibnite, eircon, hausmonnite, braunite, pyrolusite, pyrites, magnetite, tetrahedrito, htematite, kerargyrite, proustite, awenio (metallic), bomite, pyrargyrite, mispickel, cobaltine, cuprite, gersdorffite, anglesite, stephianite, tellurium, pitchblende, cerussite, bismuth glance, antimony (tnetallie), chloanthite, smaltine, tinstone, bisrauthite, argentite, wolfram, nickeline, galena, cinnabar.

Qroap 8, — Speolflc Gravity over S'6. — Copper, bismuth, silver, mercury, electrum, gold, platinum, iridium.

A rough idea of the specific gravity of minerals can be arrived at by washing in the tin dish, and this process, which in understood by every prospector, and in whose hands it can be made to yield the best results, will give sufficiently accurate results for the determination of the most common minerals. In all processes of ore concentration, based on specific gravity, the larger . stones are separated mechanically at the outset, and the grains of sand, in which the final concentration takes place, are of more or less uniform size. In dressing tin and lead ores this sorting is frequently effected by metallic sieves forming the bottoms of jiggers. The sorting in a tin dish is effected by picking out the larger stones by hand, but in testing the specific gravity of minerals they should be divided, in the first instance, into regU' lar sizes by sifting. For this purpose two sieves will be sufficient, one with eight holes, the other with sixteen holes to the linear inch ; then all which will pass through the coarser sieve, but not

THB DKTERHINATIOIt OF HINBBALS. 29

through the finer, will be of sufficiently uniform size for the testa required.

The lighter portions will first be separated by washing ; these will consist of sbale, ferruginous quartz, brown oxide of iron, pebbles of tourmaline, Ac, mostly of a lower specific gravitythan 3'&, and the heavier minerals which remain in the dish will be zincblende, magnetite, pyrites, htematite, mispickel, tinstone, wolfram, gold, platinum, <kc.

By a careful manipulation of the dish in the manner generally adopted by miners when showing the gold, these heavy minerals can be easily enough separated into three groups, viz. : — gold, platinum, &c., including the minerals of group 3 ; tinstone, wolfram, &o., including the heavier minerals of group 2 ; and zincblende, magnetite, htematite, mispickel, &c., including the lighter and medium minerals of group 2.

Some of these minerals, mispickel for instance, can be readily recognised, and, where this is the case, those which lie upstream and those below can be subdivided aa being of greater or less specific gravity respectively than 6-3, which is the specific gravity of mispickel. Where the minerals in the dish cannot bo readily recognised, a few fragments of metallic antimony or zinc, or tinstone painted white (all of which have & specific gravity of about 7), should be introduced into the dish to serve as a gauge.

Another way of dividing minerala according to their specific gravity is by meaua of liquids of high density, those most convenient in practice being the Klein Solution (Gadmium Borotnng state), and that suggested by Brauns, Methylene Iodide. The former can be diluted with distilled water, the latter only with benzole. The use of these liquids is discussed in most modern text-books of mineralogy or petrology, but th& most simple method oi rapidly determining the specific gravity of smai] mineral grains, gema, &o., is undoubtedly the Dlffiision Ootumn, devised by Professor Sollas. A small quantity of the liquid selected, at its maximum density — say 3 '3 — is poured into- a test-tube; A dilute solution of the same material is gently added to this, and fioats upon the top. Gradually, if left for from 12 to 24 hours, diffusion takes place, and Prof. Sollas has shown that a column of liquid results, the density of which inoreaaea with regularity from above downwards. If grains of' known density, such as fragments of well -selected minerals, are dropped into this column, they will fioat at diSerent levela, and will act as index-points. An unknown grain, unless its density is greater than that of the lowest layer of the column,.

will float at a certain level, where the liquid is of the aame density as itself. Its specific gravity can be found by measnriiiK the distance between any two of the index-grains, from whic£ the incretuie of deDsity can be determined for, eay, every milli- -metre that we descend in the column; the vertioal distance of the MntnowTj grain above or below one of the known ones will then serve, by a simple proportion, to determine its gravity.

It will be seen that nearly all the metallic minerals have a specific gravity between 3'6 and 8-6 — e.g., copper pyrites, chromite, pyroluaite, atibnite, iron pyrites, las. — or are lighter than copper, which stands by itself with a specific gravity of .about 8-7.

The heavier metals and metallic minerals have specific gravities ranging from 96 to 19. They are few in number, and will be easily recognised.

Lastly, the few metallic minerals in Group 1, with low speclfio gravities, are sulphates, carbonates, silicates, and phosphates, which contain a large proportion of oxygen, and they often contain water in combination with them. Amongst these are copperas, vivianite, dioptaae, chrysocolla, azurite, Im. ; none of them being compounds of minerals heavier than copper, and this for two different reasons.

In the first place, a heavy metal, such as lead, even when oxidised, will still form a heavy miner — e.g., cerussite or angleaite ; and in the second, the noble metab, which are at the same time the heaviest, do not occur as oxidised minerals, but are found only in combination with sulphur, chlorine, bromine, iodine, arsenic, antimony, or tellurium.

Amongst the non-metallic minerals a few are remarkable for their high specific gravity, in consequence of which they will be found to encroach upon the metallic aeries.

They are all found in mineral veins, although for one of them /celestine) this la the exception. Barytes is the heaviest ; its specific gravity being about 47, or that of stibnite. Witherite has a specific gravity of 4-3, or about that of tin pyrites. Celestino has a specific gravity equal to that of alabandine ; and strontianite is nearly as heavy as carbonate of iron, its apecitic gravity being 3'7.

The number of minerals whose specific gravity is not superior to 3'fl is far greater than all the metallic minerals; but their importance is not ao great, although they include all the com* buHtible minerals, all the soluble minerals, and most of the .earthy minerals; about half of them are silicates, all of which . are rather hard.

The lighter rnmemls of this series are chiefly either combustible or soluble, the heaviest combustible minerals beiog diamond, with a specific gravity of 36; graphite, 2-2; and sulphur, 3.

Amongst the soluble minerals the heaviest are sulphate of iron, 1*9, and sulphate of copper, 2'2. The others are all, or nearly all, alkaline salts, the heaviest being nitre or saltpetre with a specific gravity of about 2.

Amongst the numerous class of silicates, including silica itself, the lightest is opal with a specific gravity about 2; then come the zeolites, which are hydrous silicates containing a certain proportion of the alkalies, soda, or potash, which make them very easily fusible, and all of these have specific gravities ranging from 2 to 2'3; while quartz, on the importance of which mineral it is not necessary to insist, has on average sjKcific gravity of 3-6. Nearly ail the silicates, therefore, have specific gravities ranging between 2 and 3'5; but some are heavier, such as zircon (the heaviest of the precious stones), which has a specific gravity between 4 and 4'7, and chrysoberyl with a specific gravity between 3'6 and 3'S.

It will be seen from the foregoing remarks that the division of minerals into three groups according to their specific gravity will be easily made, and will be very useful for purposes of identification.

Minerals may be either hydrous or anhydrous, and consist —

1. Of elements alone; e.g., native metals, gold, tilver, platinum, Ac., or stdphitr.

2. Of combinations of the other elements with oxygen forming oxides; e.g., cuprite, hasmeUite, or guairtx.

3. Of combinations of the other elements with sulphur, antimony, arsenic, tellurium, chlorine, bromine, or iodine forming sulphides, antimonides, arsenides, tellurides, chlorides, bromides, or iodides ; e.g., pt/rite, alvanUt, kerargyriU, or enolite.

4. Of combinations of a metallic oxide, or base with an oxidised non-metallic element or acid forming carbonates, phosphates, sulphates, nitrates, or silicates; e.g., maiachite, lUethemle, pyrommpihite, dioplaae, &c

All chemical tests for minerals, whether with the blowpipe or in the wet way, depend upon some chemical change which is brought about, thus allowing the element, bas or acid to be recognised. These changes consist either of the decomposition of me mineral, or the formation of fresh compounds. The

following instancea will sufficientljr illustrate the character of tese changes.

If the oxide of a metal, copper for instance, is mixed with carbonate of soda and fused on charcoal, the copper ia reduced to a metallic state, the oxygen combines with the charcoal to form carbonic acid, which goes away as a gas, and any silica which is present decomposes the carbonate of soda to form a silicate of Boda, which may be looked upon as a slag.

If a hydrous mineral is heated in a glass tube, closed at one end, the water is given off and condenses as drops in the cool part of the tube.

If an arsenical mineral — e.g., mUpitfcel — ia heated in a closed tube a crystalline deposit of arsenic is formed in the tube ; but if it is heated in the air, white fumes of arsenious acid are evolved which smell like garlic.

If a drop of hydrochloric acid be placed on a carbonate, such as limestone, the presence of carbonic acid is recognised by the effervescence which takes place, the stronger acid having combined with the lime has liberated the carbonic acid in a gaseous form. To the case of very many mineral carbonates, the acid requires to be heated for this reaction.

The discrimination of minerals will form the basis of the determination of the value of an ore ; for if, by washing in a tin dish, a coarsely pulverised sample of ore which is known to certain galena and copper pyrites, the percentage of each of these minerals, which can be easily separated and roughly weighed, can be ascertained it will be possible to calculate the proportiotui of lead and copper within certain limits, and if either silver or gold, or both of these metals, be present ia the ore, these can be estimated in the concentrated galena and pyrites.

Assays are not only purely chemical or metallurgical, for in certain cases tbey can be made mechanically, as in the washing process for gold or tin ; and when ores are employed for certain purposes in the arts, their properties for these purposes can be tested on a small scale without any chemical analysis at allj and quite enough information can be gained to show whether the ore is worthy of any further chemical treatment.

The Blowpipe and IJainp or Candle. — The common mouth blowpipe sold by wholesale druggisis, or the one used by jewellers, will answer all the purposes of the prospector ; or a very useful and cheap blowpipe case, known as the Society of Arts' blowpipe case, can be obtained. The cheap blowpipe intended for mineralogical tests is made conical, and sufhcientljr large from the mouth end to the extremity (which connects with the

THR DETKSHIKATIOIT Of WNEBALB. 33

Bmall tube directed towards the flame), for the moisture to accamalate in the widest part, as otherwise it would spoil the test. It is necessary, of course, from time to time, to shake the blowpipe and expel the water. /

A common candle will be forino sufficient in most cases, but for reductions of metals, when abetter and more powerful flame is required, a mixture of methylated spirit or alcohol with turpentine or benzine will be necessary. Accordiog to the strength of the spirit, the proportions will be from 6 to 12 parts of spirit to 1 part of turpentine, or about i parts of spirit to 1 of benzine. This mixture can be burnt in the common glass spirit lamp used by chemists, but with a flat wick fitting in a suitable socket, and of about an inch in width by one-fifth of an inch in thickness.

The Ubs of the Blowpipe requires great practice, and it is

Fig. 3.— Oitdising and Foiing Plama,

Fig Flam.

probably not so difficult to acquire as it ia to explain. The blast is not obtained by sending air direct from the lungs, but

by BGoamnlatiiie it in the month, the cheeks being inflated, and then sending the air into the blowpipe hy the action of the muaclee of the cheeks. The opentiona which have to be conducted with the blowpipe consist of fudons, oxidations, and reductions. Fusion will require the use of the hottest part of the flame ; oxidfttion, a sufficient acoeu of air into that part of the flame in which the assay is placed j and reduction will retfuire air to be excluded from the assay, in which case the combustible materials in the flame which require oxygen to burn them will extract that oxygen from the mineral being tested.

The foregoing drawings illustrate the different results, either oxidising or reducing, which can be obtained by the use of the blowpipe.

The Ozldlsins and Fiuing Flame. — The wick should be out a-fresh, parallel to the inclined rim or socket, if the lamp ia used, since a charred wick will produce bright yellow bands in the blue cone of the flame, which are rich in carbon and possess a reducing action. The nozzle of the blowpipe must be placed a little in the flame, and nearly touching the wick, so as to send the air into the middle of the flame. The blast should be moderately strong, and the inner part of the flame produced will be a long pointed bluish cone, which is a little brighter near the point; the outer part will be very thin and pointed, of a light blue colour, and scarcely visible. The bright point of the inner cone is the hottest part, and in it the minerals to be fused will be placed, whilst those to be oxidised will be held a little beyond this point in the outer flame where the oxygen is plentiful.

The Beduoing Flame. — The flame of the lamp or candle should be stronger tban in the first instance ; and, if possible, the blowpipe should be used with a smaller aperture, or the blast should be moderate, so as to obtain but an imperfect combustion. At tM same time, the point of the blowpipe must not penetrate into the flame, and the air should pass a little above the wick. The flame will then take the shape of a long, bright cone, surrounded by a pale blue flame slightly visiblehe obscure inner part being shorter than in the oxidising flame.

BeagentB. — The only reagents which will be absolutely necessary are borax, carbonate of soda (calcined), and, rarely, microcosmic salt, nitrate of cobalt, and a little hydrochloric and sulphuric acid A few others are occasionally necessary, but their use is limited.

AooessoriflS. — Some platinum wire, platinum forceps, a small pestle and mortar made of agate, a small sieve, a magnet, some

The Drtbruirattoit Op Hihbr&amp;L8. 3B

small glass tube, and some good firm charcoal, practically complete the necessary equipment.

Fusibility. The ease or difficulty vith which minerals are fused, while not affecting their chemical composition, is frequently of use in their diacriniiDation. Nearly all the sulphides are fusible — e.g., etibnite and pyrites; and some ailicates containing soda or potash are also very easily fusible — e.g., teoUles; many oxides are infusible — e.ff., ehromile aad corundum — as also are many silicates, carbonates, sulphates, containing oxides of alumina, magnesia, lime, Ac., in considerable quantitiea. Zinc forms many infusible compounds, and sulphide of zinc or anoinde ia the only infusible sulphide.

Aa a rule, minerals composed of several oxides are more easily fusible than those in which only one of the infusible oxides is present. The following is the scale of fusibility generally adopted for purposes of compturisoa : —

1. Stibnile. — Fuses easily in the candle flame.

2. NatrcliU. — Fuses in the candle flame.

3. Almandine garnet. — Fuses easily even in large fragments

before the blowpipe.

mblende,

Fuse more or less easily before the , Orthoclase, f blowpipe in minute ft'agments.

6. BroTis. — Small fragments are only rounded on the edges

before the blowpipe.

7. Qnonx. — Infusible in the ordinary blowpipe flame.

Colour of Blowpipe Flake. — Certain minerals, when heated before the blowpipe, impart characteristic colours to the flame. The mineral should be used in small scales or fine powder. In the first case it should be held by the platinum forceps, and in the second taken up on red-hot platinum wire. In both cases the platinum must be quite clean, and impart no colour itself to the reducing flame. Platinum is best cleaned by heating it red hot, and plunging it into sulphuric acid.

Flame colour-tests can be made either by strongly heating the mineral in the reducing flame, moistening with hydrochloric acid, and heating again ; or, which ia better, if the wick of the candle be trimmed very short, and the mineral be heated and then brought rapidly in contact with the ii'ick, the flame coloration is observable as a flash which is very distinctive.

The Same colorations are as follow : —

36 PEtOSPECTINQ rOB HIITEBALB.

Bod Flame. — Strtnttia, Lim, or Lithia. — Of these, the lime flame is jellowisb-red, and that of atrontia and lithia purple-red. The strontia coloration does not disappear when looked at through blue glass (coloured with cobalt), while that produced by lime and lithia is extinguished.

Yellow Flame. — All compounds containing soda.

Oreen Flame. — Minerals containing baryta — e.g., harytta and wiriU — give a yellowish-green flame.

Minerals containing copper (except in the presence of cblorlne or bromine) colour the flame emerald-green.

Phosphates — e.g., apatite and pyromorphite — when moistened with sulphuric acid and held so as scarcely to touch the l.ordera of the flame, impart to it a very pale bluish-green colour. Borates moistened with sulphuric acid and held in the flame ot the spirit lamp, without blowing, colour it green approaching emerald in tint.

Blue Flams. — Chloride of copper gives a blue flame with a purple border, and bromide of copper greenish -blue. All copper minerals moistened with hydrochloric acid yield this reaction.

Violet Flame.— Some minerals containing potash colour the flame violet, but the smallest trace of soda is suihcient to destroy this colour. If a strip of blue glass is used a beautiful purple colour is seen through it.

OoLODB OF BoRAZ Beads. — A loop having been made in the platinum wire, sufficient borax should be taken up and fused in the loop to form a. clear transparent bead. A small quantity of the mineral to be tested being fused with this, the bead will be coloured if certain substances are present It should be understood that in applying colour tests either with borax beads or flames the minerals must be pure, because when complex compounds are treated the different colours are liable to obscure one another. Consequently, colour tests are only characteristic for minerals which are not too complex in composition. The following are the characteristic colours of borax beads : —

Cobalt. — Bead of a deep blue colour in both oxidising and reducing flame.

Copper.— Bead blue in oxidising flame, and red and opaque in the reducing flame.

Titanates and Tungstates. — Bead colourless in the oxidising flame, and violet-blue in the reducing flame.

Manganese. — Bead violet in the oxidising flame, and colourless in the reducing flame.

ITiokel. — In the oxidising flame the bead b violet when hot.

Thk Detebmihation 07 Minerals. 37

and pale reddiah-brown when cold. la the reducing flame the bciid becomea grey from the reduction of nickel oxide to the metallic state.

Chromiom. — The bead is always green.

UrBnium. — Bead yellow in oxidising flame, and green in reducing flame.

Iron. — In the oxidiBing flame the bead is yellow to red while hot, and from colourless to yellow when cold. In the reducing flame the bead is bottle green.

Colours op Microcosmio Salt Beads. — This salt is not so often used as borax ; it requires the loop of the platinum wire, and consequently the beard, to be much smaller, as otherwise, the fused salt being more liquid, it would not adhere to the wire. With few exceptions, the colours imparted by metallic oxides are the same as those already mentioned for borax, but they are often more vivid.

With microcosmic salt iron givea, in the reducing flame, a reddish bead ; whilst with borax, in the same circumstances, it it bottle green. Urauium, instead of a yellow bead in the oxidising flame, gives a green one.

Tests on Cbarooal. — One of the most useful and practical tests for minerals is that which can be made with a piece of charcoal, or even a small wooden stick put in a solution of carbonate of soda and burnt at one end. A small hole is made at one extremity of the charcoal, and a piece of the mineral, about the size of a mustard seed, put into it. Some minerals possessing an easy cleavage decrepitate or fly when heated before the blowpipe, and they will have to be used in powder.

The fusibility of the mineral will, of course, be observed, but the principal characters that can be detected depend chiefly upon the easy reduction, oxidation, or volatility of certain substances. A few give off a characteristic smell on volatilisation. Minerals which contain sulphur, as sulphides, yield fumes with the smell of burning sulphur ; arsenic gives a smell of garlic ; and selenium one of horse radish. t

Some metals of easy reduction, but which unite quickly'with oxygen at a high temperature, yield only a pulverulent <ning of oxide. Zinc gives a yellow coating when hot, which iWcomea white when cold. Cadmium gives a brownish-yellow coating. Other metals give, at the same time, a metallic bead and a coating of oxide. A bead of lead will be known by its malleability and a yellow coating on charcoal. Bismuth is brittle, and the coating is yellow ; antimony is also brittle, but the coating is whit&

3ft FROSFECnNO FOR UIHBBALS.

Metals can be reduced without giving any coating when they are not eaBily ozidisable, such as gold, silver, or copper. It is very easy to obaerre the malleability of a bead thus formed by striking it with a small hammer ou a clear surface of an anvil.

Some iron minerals, especially oxides, and some compound of nickel and cobalt give, when treated on charcoal, ajirtly reduced grain which is attracted by the magnet,.

Teats on CliaTOOBl with Carbonate of Soda. — Oertaln metals of leBS easy reduction will be obtained in the metallic state by mixing them with carbonate of soda in fine powder and treating them on charcoal with the blowpipe ; the minerals mentioned under the foregoing division will exhibit the same characters, and will be more easily reduced than with charcoal

Tinstone, which is an oxide of tin, mineralogically called caesiterite, is very difficult to reduce on charcoal with carbonate alone; but with cyanide of potassium it is easily reduced in small globules, which can be flattened out in the agate mortar in water, and are easily recognised.

Sulphates- — s.ff., gypnim, harytea, alunite, anglesife, &o. — when fused with carbonate of soda on charcoal are reduced with the formation of sulphide of soda (a mass of liver colour called hepar). If the fused mass be placed on a clean silver coin with a drop of water it will leave a black stain of sulphide of silver.

Tests with Carbonate of SodA and Nitre. — Manganese and chromium may be detected when heated oo a piece of earthenware or platinum, after having been mixed with the above reagents, by forming, the first a greeu, and the second a yellow mass. Nitre is necessary in these teats as, containing a large quantity of oxygen, it supplies it for the formation of the compounds, which are both salts containing a large proportion of oxygen — viz., manganate and chromate of soda.

Teata with ITitrato of Cobalt. — Nitrate of cobalt dissolved in water, and used in exceedingly small quantity, helps to discriminate between certain white minerals — e.g., kaolin, Tneeraekaum, magnetite, dolomite, ka. The mineral is reduced to powder and moistened with a drop of a very tight solution, and then heated before the oxidisiiig flame of the blowpipe. Kaolin and other minerals containing alumina assume a rich blue colour, while meerschaum and other minerals containing magnesia become flesh coloured. Oxide of zinc, under the same circumstances, becomes green, and this can be tried with the white coating obtained on charcoal by reducing an ore of zino with carbonate of soda.

luuile

Tbk Det8Rhiitati0V Of Hinxralb.

Tests in aiasa Tubes. — These can be better made over a spirit lamp, so as to avoid the deposit of soot on the glass ; but they can also be made with the blowpipe flame, provided it is used carefully, avoiding too sudden a heat, which would break or fuse the glass. The presence of water in minerals will bo detected in this way, and the water collects in small drops in the cold part of the tube. Hydrous minerals which are likely to give this result will be easily found in the list of minerals.

Some minerals containing sulphur, arsenic, antimony, tellurium, and selenium often give a characteristic deposit.

Minerals containing mercury can also be tested in this way, as by adding a little carbonate of soda, sometimes with cyanide of potassium, a sublimate of metallic mercury will be formed in the cold part of the tube. A little charcoal should be added to arsenical minerals.

Organic combustible minerals generally leave a deposit of carbonaceous matter at the bottom of the tube, and the volatile hydrocarbons condense in the cooler part ; the tube should therefore always be long enough to allow for this condensation, minerals which yield a characteristic smell will be best tested in this way.

DETEBMINAnON OF MINERALS.

The present scheme will be found to answer in most case for the identification of minerals of common occurrence, but will not discriminate between the many rarer species. Fully a thousand minerals have been described from time to time, but in this book it is not proposed to deal with more than about one hundred which are of common occurrence. In any case, however, the system adopted will give some clue as to the nature of an ore.

The physical chai'acters already described may, in some cases, render it unnecessary to follow out the course of the tables given below, but, when any doubt exists, the systematic tests enumerated are best followed.

Minerals have been divided for purposes of identification into

(a) Minerals with metallic lustre. {bj Minerals without metallic lustra

Some doubtful minerals exhibiting a semi-metallic lustre — e.ff., siwMende — are placed in both groups.

An attempt has been made to form groups of the useful minerals, so that each group could be easily recognised by one or

more characters. All the ores of copper, for instance, yield a bead of copper Then treated on chai-coal with aoda before the blowpipe, BO that the group of copper minerals can be separated at once and the different minerals identified in the manner described in the chapter on Copper Ores.

Many minerals are mentioned in the tables which have no apparent value to the prospector, but had a scheme of determination been drawn up for only the most common minerals, say fifty in number, mistakes would have been unavoidable when any rarer minerals, not so included, were found. In the present scheme all minerals of any importance to the prospector are included as well as many which, while of no economic importance, are likely to bo met with, and no time will be lost in discrimination if the directions are intelligently followed. As regards the metallic ores, they can he classed as silver, copper, lead, Ac., without pushing the inquiry any fui-ther if it is only desired to form an estimate of the nature of the ore and not to determine the mineral species.

Although, as already stated, some of the minerals included in the tables would not, at first sight, appear to be of any importance to the prospector, they are, many of them, of indirect importance as constituents of certain rocks. It will be seen how intimately connected with the different mineral deposits are the characters of the rocks in which they occur, and a prospector who would ooquire the scientific knowledge which underlies his business must learn to distinguish the different classes of rocks, the first step towards which is the recognition of the minerals composing them. It is perfectly true that in prospecting for valuable ores a thorough knowledge of the eruptive and other rocks is of scarcely less importance than the discrimination of the ores themselves.

Hinerals vith Metallio Iiustre.

The native metals which are malleable may be recognised at once ; they are platinum, gold, sUvtr, and copper. Mereury and and the native amalgams can also be easily recognised. Silver glance alone, which is so malleable and sectile as to be mistaken for.lead, would have to be further tested for sulphur with the blowpipe to be identified with certainty; but native lead is extremely rare, and silver glance is not likely to be confounded with silver. Platinum will be recognised by its infusibility before the blowpipe.

THE DETBBUltTA-rtON C

MiiTERALa Easily Fusible or Volatile.

I. Before the blowpipe, give smell of garlic due to arsenic.

{a) With soda on charcoal give, before the blowpipe, a bead of copper (see Copper Ores and Silver Ores iov polyoaiite).

(6) With borftx give, before the blowpipe, a blue bead due to cobalt (aee Oobalt Ores).

N.B. — Some nickel ores occoaionftlly contain enough cobalt to give this reaction, but otherwise they give a brown bead.

(c) Before blowpipe, do not give the above results, hub in a glass tube afford a crystalline sublimate of arsenic.

If the mineral, after having been heated for a long time before the blowpipe on charcoal, melts to a black magnetic bead it is mitpickel ; bat if, in Hie tube, it is oompletely volatile it is native artenic.

ir. Before the blowpipe, give off abundant while JuJnes without tell, due to antimony.

N.B. — A smell of snlphur or arsenic may sometimes be observed in minerals belonging to this group if these substances are present in sufficient quantities, but the white fumes of antimony are characteristic. At the commencement of the operation the charcoal is covered with a heavy white coatine which does not colonr the flame ; but this must not be conhiunded with the ashes of the charcoal which are also white, but are very light.

(a) With soda on charcoal give a bead of silver (aee Silver Ores).

(6) On charcoal with soda give a bead of copper after the lead present has been oxidised ; leaves also a dark red coating on the charcoal (see Copper Ores ; boumonite).

(c) On charcoal, before the blowpipe are almost, or entirely, Tolatile.

N&ttTe antiniOIiy is entirely volatile, leaving a white coating ; there is no smell of sulphur, and the metal is tin-white.

Stibnits (see Antimony Ores) is lead-grey to steel-grey, and is also entirely volatile, but focus a black slag at first, and a smell of sulphur can &lso be detected.

Jamesonite and Zinekenlte (see Lead Ores) ore lead minerals containing antimony, are net of common occurrence, and are not entirely volatile. With soda they afford a bead of lead as also a smell of burning ulphur, and, in the oxidising flame, a yellow coating on charcoal.

ff.B. — Some galenas when miied with atibnite give the same reactions ; but galena will be recognised by its three cubic cleavages, while zinckenite ia not cleavable, and jamesonite has only one cleavage.

Ill, Be/ore the blowpipe, give a smell ofgulphtir without white Jumes, and treated with eoda on charcoal form an alkaline aulpkide.

If.B. — The bulk of carbonate of Kxla med ihauld be three times that of the Bua; ; when the mass is melted it U separated from the charcoal with tho point of a knife and placed on a silver coin with a. drop of water. If it praMut a brown Etain will be formed on the ulver,

(a) On charcoal with soda, before the blowpipe, give a bead of copper (see Copper Ores and Silver Ores ibr Stromegerine).

Stromeerine will be identified bj diaBolving in nitric acid and precipitating with Bait, a white Qoccnient precipitate ra chloride of diver oeing formed.

(b) On charcoal with soda, before the blowpipe, give a bead of silTer (see Silver Ores),

Silver g'lance ii easily aectile and very fnaible,

(c) On charcoal with Boda, before the blowpipe, give a malleable bead of lead and, in osidiaing flame, a yellow coating in the charcoal (see Iad Ores — Galena).

(d) Treated as above give a brittle bead of metallic bismuth (see Bismuth Ores).

Treated as above yield a magnetic moss.

Millerite {aee Nickel Ores) us a rare mineral of a brass-yellow coloor and occurs in capillary crystals.

Pyrites (see Iron Ores) occurs as brilliant crystals or massive of a light brasB-yellow colour, and is hard enough to scratch glass.

Steiberglte (aee Silver Oree) is of a bronze -yellow colour, doe* not scratch glass, and yields a magnetic bead containing silver,

NleOpyrlte (see Nickel Ores] is bronze-yellow or copper-red, does not scratch glass, and with microcoemic salt forms a bead which ia red when hot, yellow when cold.

PyPrhOtine (see Iron Orea) is bronze-yellow or copper-red, does not scratch k'ii >nd with mtcracoBmic salt gives a green bead in the reducing flame, while in the oxidising Some the colonrs are the same as for nico-

e the blowpipe, a smell of horae-radish ia

Seleninm occurs combined with lead, copper, mercury, and silver forming minerals which are very rare, and are not again moiiti<'ned in this book.

V. On charcoal, before the blowpipe, give a tffiite coating tokich beeomtt green or greenish-blue be/ore the reducing me.

When heated in a glass tube with excess of concentrated salphnric adjl the eolation assnmea a purple or hyacinth colour, which disappears when water ia added, a, greyish-black dust falling to the bottom uf the tube. This dust is tellurium, a rare metal which occura in many minerals, especially with silver, gold, and Icsd (see Tellurinm Ores}.

VI. A few minerals which melt more or les easily </o not answer to any of the ftfrtgoing characters and will be considered

THE DBTEltHtNATIOtI OF HINEBALS. 43

(o) Reddish silver-white, brittle; specific gravity 9-7 (heavier than copper), very brittle and easily fusible ; native biamuth.

(b) Ked, dust cherry-red, brittle. On charcoal with soda yield a bead of copper. Cuprite (see Copper Ores),

(c) Black, not easily fusible or nearly infusible.

WolfPSJn (bcb Tnngsten) is black, dust dark brown-red or brown-black with a semi-metallio lurtre j its specific gravity is 7 to 7 '5 ; and It ia fuaible to a magnetia globule with crystalline earface.

HEematite (see iron Ores) u black to red in colonr and the dost red. It ii practically infiutble, bnt before the tdaciiig Hame become magoetic.

Hlnetite (see Iron Ores) is black, and the is black ; it is magnetic, and fusible with difficnltj.

Psllomelane (bbs Manganeie Ores) ia black, and the ia black ; with borax it give a violet bead due to manganeae ; or a green maaa with nitra and carbonate of aoda.

M1NBHAL8 IkpDBIBLK or FuSlBLK WITH MORE DIFFIC0LTT THAU ObTHOOLABB HOT VolATIlK.

I. On ekareoal, tn reducing flame, become magnetic, or are magnetic in their natural slate (see Iron Ores).

2f. B. — Titanic Iron and aome chromitea would be included here ; and linoblende aometimea containa enough Iron to become magnetic under the above circamatancea, bnt if treats with hydrochloric aeld zjncblende evolve* a smell of rotten egga due to aulpharetted hydrogen.

II. WOK borate a tmall quarUity of the mineral gives a vioUt bead ; does not become magnetic as above (see Manganese Ores).

III. Minerals wkiehdo not anwer to the above characters. (a) Minerals pitch black, hardness over 6.

(i) Minerals, lead-grey or iron-black, very soft, will mark on paper like a penciL

Holybdenltfl (see Molybdenum) ia lead-grey in acaly and flexible laminee.

Graphite (see Carbon) ; iron black, not generally scaly.

Minerals without Uetallio Xiustre.

MiNEBALS Soluble in Wateb.

I. Found in JetaUio Mines.

(a) Colour blue ; with soda on charcoal, before the blowpipe, yield a bead of copper ; sulphate of copper (see Copper Ores).

,i?dl

Prospect Ino Por Uinerals.

) Colour green ; with soda on charcoal, before the blowpipe,

i a magnetic mass j stQpliRte of iron {see Iron Ores).

(c) Generally colourlesB ; found chiefly in old metallic mines ;

before blowpipe, on charcoal fuse, and give white incrustation,

which turns green with nitrate of cobalt ; goslarite (see Zino

The moat common of the above metallic sulphates, and most likely to attract attention, is the salphate of copper, bnt snlphate of iron is also common in Bome mines, and goalarite is not infrequently met with.

II, ot generally found in metallic mines.

MiNBRAte Insoluble in Water,

I. Bum or volatilise be/ore the blowpipe.

N.B. — No mineral harder than quartz will ocoar in this group, (a) Smell of sulphur in burning.

Native sulphur, characCeriatic yellow colour, and very brittle. Clnnabaf (see Mercury Ores) of a deep red colour, entirely volatile. With aoda gives drop of mercury.

(fi) Smell of garlic in burning ; due to arsenic.

Orpiment (aee Arsenic Ores) of a yellow colour, with a resinoua, greasy, or nacreous lostre.

Realgar (tee Arsenic Ores) of a red or orange colour, with n reainons or greasy luatre.

{c) Volatiliea, giving off dense white fumes. Oxides of antimony (see Antimony Ores).

{d) Bum or volatilise without exhibiting the above peculiarities. See Carbon Minerals.

II. Before Uie blowpipe melt more or less easUy.

The least fusible mineral of thia group is orthoclsee, which fuses only when in amall scales or fragments. All those minsrals which in very thin scales can only be ronnded on the edges will be considered as infusible, or nearly so.

(a) On charcoal with soda, before the blowpipe, yield a metallic bead or powder, noa-magnetic.

and colour the Same either blue or green.

not in&raietlo.

HolTDdlte (see Molybdenum Ores) ia uot reduoed to t, bead, bat oau be obtained aa a powder by cnubing the fiued nuBS and WMhing. Tha mineral ia earthy and yellow id colonr, and the coating become* olue [a the reduoiog flame, bnt the colonr ia transient.

(b) On charcoal with soda yield a. magnetic mass, but it is Eometimes necessary to reduce a considerable quantity before the magnetic properties can be observed.

Cobalt Bloom (see Cobalt Ores) and seTSFal arsenlates of iron and nickel (see iron and Nickel Ores) aSbrd a smell of garlic on charcoal before the blowpipe, of wbioh cobalt bloom may be dislioguUbed by the bine coloration it imports to the borax bead.

The are several other minerals which do not afford a smell of Rarlio, oa

Wolfram (see Tungsten) ; aa heavy as tin ore. Vlvlanlte (see Iron Ores) ; scratched by the noil and blue in colour. Siderlte (see iron Ores) ; scratched by a kaife, buff in colour, and powder effervesces with hot acid. Ldpldolltfi (aee Mioos) ; scratched by a knife ; colonr, white, violet, or

EaFtby Hsematite (see Iron Ores] ; scratched by a knife ; gives t, characteristic red streak and powder.

RhodOnltO (see Manganese Ores) ; not scratched by a knife ; generaUy flesh red, powder rosy white ; with borax gives a violet bead duF tc manganese, and a green mass with nitre and carbonate of soda.

QapnetS (see Gem Stones) are generally orystaUised, anH are harder than quartz.

if. B. —There are some other silicatM which oooasionally give a magnstia glaas when fused before the blowpipe — t,g., bomblendQ, aUfitd, and some other ferruginous minerals, such as black toarmaliue and epidote. Among the foregoing minerals lepldoIltS and rhodonltd will only yield a tnagaetic mass in rare oaiea when they contain much iron, so they will also appear In another group.

(e) Minerals which yield a coloured powder and on charcoal with soda do not yield a metallic bead or magnetic mass.

UltramaFine or Lapis Lazuli (see Gem Stones) is bine, with a binishwhite powder, and Qan be scratched by a knife.

N.B. — A closely allied blue mineral, hauyne, answers to this description, bat is only found in volcanio rocks, and ia transparent, while lapia lazuli is opaque.

Rhodonite (see Manganese Ores) is not scratched by a knife, U generally fleah-red, and the powder rosy-white, while it exhibits the manganesereactions with borax, ko.

Garnet (we Oem stones); generally red-brown or black in colour ; is not scratched by the knife ; genery orystalliaed ; and apeoiQc gravity about 4.

Cassltent (see Tin Ores) ; red, brown, orange-yellow in oolonr, or black with a light grey or brown powder ; easily reduoed with cyanide of, potasainm on onarcoal to metallic tin.

PBOBPBOTtlire FOB MINERAI&

Jd) Miaerals which field a white powder aad on charcoal with a do not yield a metallic bead or magaettc mass. Boraelte (aee Qem in cabes, ftc. , and ia bont .as hard at quartz.

ToUPmalltie (see Gem Stones) oconrs ia priBnu. This division iDcludes a great number minerals whiah are Bcratched by quartz, some of which are componnda of lime, baryta, atrontia, to., euob as anhydrite, selenite or gypsum, barytas, atrontianite, withorite, cryolite, fluor spar, and apatite,

none of which, with the exception of fluor bt and apatite, are harder thau barytes. It alio includes a etill greater immber of Bilicates, which all, with few eiceptioni — e.g., lepidoUte and mageslte— are harder than

baiytea, and moat of them harder than floor spar. These two division) will be considered separately, under Insoluble saltS and sUicates, and they may mostly be recosniBed by their phyeioal characterB md the coloun they impart to the blowpipe flame.

IIL Before the blowpipe, inftisible ; or futile with more dijtcvliy than orlhoelaae, being only rounded on the edges when used in very thin tealee.

(a) Aa hard as quartz or harder than quartz.

if.S,—All the gems proper are to be inclnded here, except opal, which -is scratched by quartz ; and toarmaline, which, in some varietiea, is fusible. Tin ore is sometimes aa hard as quartz, and being fusible, with great difficulty might be found here. It will be reduced ou charcoal with cyanide of

.Andaluslte [aee Gem Stones) is usually found in atont aqoare prisms ; with nitrate of oobalt on charcoal the powder assumes a blue coloar.

Disthene of Cyanlte (see Gem atones) also assumes a blue colour with nitrate of cobalt, and usually occurs in fiattened prisms which are white or blue in colour.

Quartz and the other gems do not awnme a blue colour with nitrate ot cobalt.

(b) Scratched by quartz; powder or streak coloured. Siderite (see Iron Ores) ; powder light brown ; eServescea with hydrochlorio

acid when warmed.

Dlallogite (see Manganese Ores); powder reddlah-whlte ; borax bead-

Limonite or Brown Hsematlte (see Iron Ores) ; powder yellowishbrown ; usually kidney shaped, concretionary or stalootitio ; on charooal with soda forms a magnetic mass.

BOff Iron Ore (see Iron Ores) ; powder ochre-yellow ; mineral earthy. -On charcoal with soda forms a magnetic maoa.

Chromlte (see Chromium) ; powder brown ; mineral, black with a lustre approaching metallic ; borax beads green. On charcoal with soda forms a magnetic mssE.

Pitchblende {see Uraninm Ores) ; powder olive to brown ; colours of nucrocoamic salt green when oold. On charcoal with soda does Aot form a magnetic mass.

The Determination Ov Minehalb. 47

CflSSiterite {see Tin Ores} ; powder light grey or brown ; ylelda oietAllia tin with cyanide of potsminm on ch&rcoal.

ChlOFlte (see SilicAtea of Magneaik) ; colour of powder greenish j mineral, ereen in *mall loalea.

.B.— Highly coloured Herpentine will give a very light atreak or powder, much lighter than the deep green or brown of the rock, and it will appear practically white compared with the colour of the rock itself. Some aerpentinea and the nickel ores of New Caledonia |ailicate of ulckel <uid macueaia) will be doubtful in this case, and therefore have also been included in the next group of the table. The nickel ore ia apple-green; !. 1... ig ooQuderably lighter, but becomea green again when moistened.

(c) Soratohed by quartz ; powder or streak wbit or Tcry pale

StFOntlaillte (aee Insoluble Salta) eflerreBcea with acid and colaura the "blowpipe flame crimson.

6 (MS Inaoluble Salta) effervesces with acid and colours the blowpipe flame yellowish-red.

BaFytocalGlte (see Insolable Salta) efferveaces with acid and ooloura the blowpipe flame first red and then yellowish-green.

Dolomite (aee Insoluble Salts) efferveaces with acid only when heated, and has a charocteriatic pearly lustre.

Apatite, Mica, Cassltente, Hutlle, SeFpentlne, and Silicate of Mickel donoteOervesoewithaoidand wUIbefoniid under their respective

Iq illustration of the use of these tables, a crystal of oeruABite <or carbonate of lead may be taken, and it will be foimd —

1. It is a mineral without metallio lustre.

3. It does not burn or volatilise.

4. Before the blowpipe it melts more or less easily.

5. On charcoal wiUi soda it yields a metallic bead which is not magnetic.

6. The bead is lead, being malleable and giving a yellow coating oa charcoal. The mineral, therefore, belongs to the lead ores, and a reference to the chapter devoted to lead will easily distinguish oerusBite from other lead minerals, lor it efiervesces in powder with hydrochloric acid, especially if

-warmed.

n,g,t,7.cbyGOOglC

Chapter Iii.

It is difficult to separ&te these two different claaaeB of minerals, as some whicli form extensive rock deposits are commercially valuable ; besides which it is inadvisable for purposes of discrimination to treat them separately.

Soluble Salts are not of common occurrence, although some, like rock salt, occur as beds of great commercial value in sedimentary formations; while others, as natron or carbonate of soda, occur as surface efflorescences in dry countries, such as Kgypt, where they have no chance of being dissolved and carried away by rain.* The varied uses of rook salt are well known; its principal application is in the soda industries, but the consumption for domestic purposes is alao considerable.

The moat important potash mineral, carnallite (which is a chloride of potassium and magnesium), occurs in the upper beds of rock salt at Stassfurt in Germany, and is scarcely known elsewhere; while the most important mineral source of aitre is nitratine, or cubic nitre, a nitrate of soda found in Peru and Chili, the working of which has during late years formed a most important and remunerative industry. In the district of Tarapaca, at a height of 3300 feet above the sea, the ground has been for about 40 leagues covered with beds of this salt, which were at places several feet in thickness, and associated with gypsum, common salt, Glauber salt, and the remains of recent shells.

Sulphate of magnesia or Epsom salt, which is much used in medicine, occurs as an efflorescence in mines, especially where pyrites has undergone decomposition in presence of maguesian rocks. It is also found in caves.

Another soluble salt of value is borax, which is found crystallised on the basins of dried-up lakes in Thibet and California; in the latter locality, in the Calico district, some important beds of borate of lime are being worked which are interstratified with shales.

A remarkable deposit of trOTia, a carbonate of soda containing water than natron, occurs in Adair Bay in the Qulf of California. It is found as a cruat from 12 inchei to 25 incliea in tbiokneaa on the anrface of a small lake about 50 acres in extent, the waters of which are saturated wiUi carbonate of soda ; the lake oacnpies a depreasion in a wide extent of sand dunes. The mineral has oryBtalliBed on the surface of the mother UguoT like ice on the aurfooe of water.

Rook-Fobhiho Add Mon-Metaluo Hiveiuls, 49

The Boluble metallic salts, such as the sulphates of iron, copper, and zinc, are easily known ; they are found in mines where iron pyrites, copper pyritefi, or zinobleii<)e have become oxidiBed, and frequently occur in solution in the waters of certain mines, rendering them quite unfit for domestic purposes. In Southern Spain, the river called Bio Tinto has been so named on account of the quantity of sulphate of copper held in solution by it.

It 'wilL be readily understood that waters circulating below the sur&ce of the ground dissolve some of these salts, and when they reach the surface aa springs frequently contain a greater or less quantity of them in solution. These mineral springs are classified according to the minerals they hold in solution.

Kartht Oabbonatk akd Sulphates, with Apatite, Flcob Sfab, and Cryolite.

In this group are included fifteen minerals, only a few of which are very common — viz., calotte, gypsum, and magiiealte, which are of universal ooourrence ; while some of the others are abundant in certain localities. Cryolite is only known from Greenland, but being a valuable mineral it cannot be omitted.

Five non-metallic minerals may be considered as lode-forming minerals ; the most important of these — viz., quartz — will be subsequently described. The four others are osilalte, bar;tes, witherite, and fluor spar; while others — e.g., apatite — occur less frequently in reefs.

Carbonate of lime crystatlises in two distinct systems, and the name of caloite or calc-spar is reserved for those crystals which, while occurring in a great variety of forma, can all be reduced by cleavage to a rhombohedron. Calcite occurs in reefs, and sometimes, especially in limestone countries, accompanies auriferous quartz, and even carries gold itself, as at Qnndagai and Tuena in New South Wales, and Gympie in Queensland. It also occurs crystallised iti rents and fissures in limestone.

Although crystallised calcite occurs in metalliferous veins in many countries — e.g., Derbyshire and Oumberland in England, and the Hartz in Germany — the largest crystals are found in Iceland, where it is very pure and transparent, and is called Iceland spar. It exhibits the property of double refraction most perfectly, and on that account is used in the construction of some optical inetruniente. Probably Iceland can boast the largest natural crystals in the world, since specimens of calcite are recorded from there in single rhombohedrons six yards in length.

The other species of carbonate of lime is called aragonlte

PB08PI0n50 rOB KllTBRAU.

BAKTH? CARBONATES AND SULPHATES, WITH APATITE, FLUOR 8PAB, AND CEyOUTB.

Btm.

3i-*l

H-H

Stroutiuiite, Witbarite, .

B&rytoealoite, Anhydrite, .

Celeitine, . Buytes, . Floor ipai, .

u

PhMpbKto of Ca with fluoride or ohloride ot

OryttftUof ten curred

and Buddle ahaped ;

In Mrpentine, not

COmnion. Laitre omat

Dsoreoiui on cUv-

If bnmed give lime. Priams, often

KcoiiFa. Loatre greaay

fnctare. Loatre greaay

fisctme; occnra

Needle eluded ; yelloviah

-white. Generally found with

gypnia uid rock

When bamed avells np.becomeaopi and form* pu of Pari*.

Cryatala white, often with a bluiah tinge.

Very heavy; 00

Lnaire greaay cleaTaga laoea and fraetnre; an-'-

Al, Alnmininm ; Mg, Magoesinm ; 8r, Strontinm ; Ba, Barium ; Ca, Calainm; Ha, Sodium,

Bock-Fobhing Asd Noh-Kbtallic Minerals. 51

because some of the most perfect cryBtAla have been found in Aragon in Spain; it ctyatollises in prisma. Aragonite forms many of the stalactites ia limestone oaves, and it ocours in radiated kidney-shaped masses in cavities in basalt. When recently deposited from lime springs and stratified in beds it forms what is known as OEcareouB tufa or travertine, but calcite also occurs in similar deposits.

Before the blowpipe aragonite whitens and falk to pieces, but in other respects resembles caloite. The reason for this behaviour before the blowpipe is explained by the fact that under the influence of heat aragonite is changed to oalcite and splits up into a number of small rhombohedrons.

Limestone forms extensive sedimentary deposits in beds of all ages, and when subjected to metamorphic action takes a crystalline form, the pure varieties which are white and fine grained, and are suitable for statuary purposes, being called Baooharold marble. Marbles assume every colour and shade according to the substances which are mixed with them ; in the Devonian and Carboniferous formations, where fossil corals are plentiful, marbles are found which exhibit, on polished sections, the starlike forms of the corals of which they are composed. "When a marble consiste of broken fragments which have been snbeequently cemented by an infiltration of carbonate of lime it is called a breoointed marble.

Marbles which are pure white or of a characteristic colour will always be valuable, but for a deposit to be properly worked the means of transit must be easy. The stone must be free from quartz veins or fossils transformed into quartz, and be easily obtained in blocks or slabs of large size, suitable for ornamental work. Marble has to be sawn with toothless stone cutters, bnt softer limestones, which hare not been metamorphosed, can easily be cut with a toothed saw ; these softer limestones are called freestones, and are used for building purposes; y they usually occur in the later formations, such as the OoUtio/ limestone of Bath, or the Oamaru stone of !New Zealand.

Litbphio atone is a very compact and fine-grained nmestone, free from veins and fossils, easily cut into large slabs, and of a light colour. A lithographic stone possessing these qualities is not obtained in many places, and will always command a good price.

limestones are also of value for smelting purposes or for burning for quicklime, and, according as they contain certain proportions of other materials, may be of value for the manuftctnre of hydraulic lime or cement. It is not, however, possible

for the prospector to determine these properties ia the field, and samples should always be submitted to a chemist, and, if sufficient inducement offers, to cement manu&cturers.

The next most important mineral of this group is gypsum, which is extensively used for building purposes. It is a hydrous sulphate of lime, which loses its water and falls to powder when burnt ; this powder, which is perfectly white when free from iron, possesses the property of re-absorbing the water lost, and in a very short time of assuming again the solid state, expanding slightly in so doing. It is this last property that renders plaster of Paris so valuable for obtaining casts.

Gypsum occurs in lenticular masses of considerable extent in the fresh-water Tertiary formation at and near Paris. The large arrow-head shaped crystals which are to be seen in all collections of minerals are exceptional in these deposits, the whole mass being in a compact sugar-like state. Gypsum also frequently exists in groups of crystals arranged around a centre, and is found in isolated crystals in salt lakes, such as occur in South and Western Australia, a small proportion of sulphate of lime being present in the water. It is also found crystallised in clay beds in New South Wales and elsewhere. The incrustations, which form in boilers on board steamers, are mostly composed of sulphate of lime. Gypsum is occasionally found in mines where deoomposltion of pyrites has taken place in the presence of calc spar or limestone.

Anhydrite, which differs from gypsum by the absence of water, occurs in rocks of various ages, especially in limestone aud those which contain gypsum, and is also very common in beds of rock salt ; gypsum is often found to proceed from the decomposition of anhydrite.

The fibrous structure and silky appearance of some minerals has already been explained, and reference made to the occurrence of calc spar and gypsum in this state, as well as to their value for ornamental purposes. The fine-grained forms of both these minerals are sometimes called alabaster, but the term is generally applied to gypsum. The two varieties can be readily distinguished, as gypsum can be scratched by the nail, while calcite cannot.

Dolomite is carbonate of lime ajtd magnesia, and crystallises like calc spar. Dolomitic limestones contain variable proportions of magnesia aud lime. Very many limestones are thus, partly or wholly, dolomitic, and some of them burn to very good hydraulic limes. The dolomitio limestone of Ohio, U.S.A., is of special interest as forming the reservoirs in which the petroleum

Bock-Pobuiko Abd Nos-Mbtallio Minerals. B3

of that field ia stored, it being (argued by geologists that the dolomitbation has resulted in innumerable small cavities being left in the limestone, which ia thus enabled to act like a sponge,

U Enesite is carbonate of magncBia. It is rarely crystallised, occurs in talcoBc schists, serpentine, and other magnesian rocks, , and is used for the manufacture of Epsom salt Pure white nagnesite has been observed to arise from the spontaneous decompoBition of the heaps of refuse from sJiafts on mines ; pebbles are quickly cemented together by it, and timber, old tools, &c., encrusted.

Hydromagnesite, which differs from magnesite by containing water, occurs in earthy mosses under similar conditions to

Barytes and Witherite are respectively sulphate and carbonate of baryta, and both occur in veins, sometimes with galeoa or copper ores, as in Spain. Barytes is sometimes found in veins alone, and is mentioned in association with gold at Mitchell's Creek, New Sonth Wales. Both barytes and witherite are used in the preparation of baryta and its salts, but witherite is far the more valuable mineral. It is used in sugar refining, and also in the manufacture of plate glass.

Celeatlne and Strontianlte are sulphate and carbonate of strontia, and are used in the preparation of the salts of strontia for red fireworks. Cetestine is usually associated with limestone, gypsum, rook salt, clay, and sulphnr, while strontianite is found with galena and barytes in veins. The strong crimson colour imparted to the flame oy these two minerals will always easily identify them.

The three minerals yet remaining to be dealt with under this

§roup are apatite, fluor spar, and cryolite, all of great value for ifferent purposes. Apatite is a phosphate of lime with calcium chloride or fluoride, and occurs under the following conditions : —

1. In metamorphic strata, where it is supposed to have originated from animal matter {Dana). It thus occurs in the lAurentian rocks of Canada in green crystals of large size, and is also found in !Norway under similar conditions.

2. As on accessory mineral in metalliferous veins, especially those of tin, and beautifully crystallised and of various colours in many eruptive rocks.

3. In veins by itself, mostly in limestone, but sometimes in granites and schists; e.g., Spain and France. In these deposits apatite also occurs as concretions, sometimes showing a radiated structure, but of an earUiy appearance externally.

C4 PBOBPECTiira roB hiiterals.

4. In sedimealacy formatioos where a considerable aceumalation of fosaila has provided the phosphate of lime. In these deposits it ocoare in two principal forms, (a) Ooprolites, whidi are excreta of large animals, especially Saurians ; and (6) concre' tions formed at the expense of the same coprolites, together with shells, bones, &c. The richest of these deposits are from Lower Cretaceous to Lower Jurassic in age, but phospbatio deposits are ' found and worked in sedimentary deposits of all ages.

Phosphate of lime is very valuable aa a manure, and the deposits included under Groups 1, 3, and 4 are worked for thia purpose.

Fluor Spar is a lode-forming mineral, sometimes alone, but also associated with other minerals, especially tin ore and galena. In the lead mines of Derbyshire and Cumberland, which are in limestone, it is found in beautiful crystals of con* spicuoua colonrs, and, when obtained in blocks of sufficient size, is worked into vases and other ornaments. In Derbyshire the blue and purple varieties are known to the miners aa "blue John."

The presence of fluor spar in metalliferous veins is a great advante, aa it ia a valuable flux for smelting, and when found in veins by itself it is mined for the same purpose. In addition to its value as a flux it is also used for preparing hydrofluorio acid for etching glass.

Cryolite also contains fluorine, but combined with aluminium and sodium. It forms very fusible compounds, and is used as a flux; but its principal application is for the manufacture of aluminate of soda, and as a source of the metal aluminium. It is also used in America for the manufacture of a white glass which imitates porcelain.

The two hardest of these minerals are apatite and fluor spar, and the heaviest are thoe containing baryta and strontia. All minerals of thia group will answer to one of the following tests: —

1 . Eflerveace with acids either hot or cold ; Carbonates.

2. Yield a stain on ailver when fused with carbonate of soda. and moistened with water ; Sulphates.

3. Etch glass when treated with sulphuric acid in a platinum or lead dish; Fluorides.

4. Colour blowpipe-flame dirty green when moistened with sulphuric acid, and with magnesium wire in a closed tube evolvethe disagreeable smell of phosphu retted hydrogen; Phosphates.

A reference to the characteristics in the table will serve readily to distinguish one from the other by the blowpipe tests already given.

n,g,t,7.cbyGOOglC

E-FOBItIKO AND NOIT-IIETALLia

QdABTZ AMD Ofal.

Quartz is the moat commoa substance with which the prospector has to deal, aad it is therefore aecessarj to explain its characters. It is, ohemicallj, silica or silicic acid, a' compound of silicon and ox7geu; and it may be remarked that silicon does not exist in nature, except in ooDtbinatioii with oxygen, forming quartz and silicates.

In the Dlast furnace silica is not fused, but Is reduced in very small quantities to silicon ; whilst fusible silioates or slags are also formed. It is only by combination with oxides, such as lime, alkalies, metallic oxides, &c., that silica forms fusible substances in the blast furnace or before the blowpipe, and these fosible substances ore termed Silioatea.

The highest temperature which can be produced artificially is obtained by th.e combustion of hydrogen in oxygen, and this osybydrogen flame is employed to fuse both platinum and quartz, which are only fusible uader the same conilitions. Gold or silver at such a temperature fuse immediately and volatile, forming a dense vapour.

The Stanhope pocket microscope, which Is only about an inch in length, is made with a drop of fused quartz with one face cut ; fused quartz has a specific gravity of 2*2 only. The specific gravity of the quartz iu reefs, as well as that which occurs in granite and some of the acidic volcanic rocks, such as rhyolite, ranges from 2'5 to 2*8, pure quartz giving 2*65. The only natural form of silica known which has as low a specific gravity as 2*2 is a mineral called trldymite, which occurs in some of the highly silicated rolcanic rocks, such as rhyolite and trachyte, and crystallises in small hexagonal tables, often occurring in groups of three crystals. Its chemical composition is the same as quartz.

These observations are of interest, because they show that, notwithstanding the views still held by many practical men, the quartz which forms our reefs and occurs in granite and other eruptive rocks has never been in a state of fusion.

Quartz can be produced artificially ia microscopic crystals by the aid of superheated water ; while the geysers sufficiently illustrate the solubility of silica in hot water chained with carbonic acid and its deposition therefrom. Quartz is always cryatalline, for even in quartz reefs, where the mineral is compact, it is confusedly crystalline ; while f int and the chalcedonies are minutely crystalline when seen under the microscope, but probably contain some amorphous opaline matter. Agates, which

fi6 PBOSPBCTtBa FOB HINERAtS.

are the only varieties of quartz of anj value, consist of layers which are altematelycrystalline quartz and variegated chalcedony.

In opal water is generally present, although Dana calls it unessential, and in the siliceouB deposits from geysers the silica is still combined with water and the specific gravity is lower, ranging between 1*9 and 2*3.

Common opals are of frequent occurrence in eruptive rocks and in veins at the contact of serpentine with other beds. Even in sedimentary formations where siliceous concretions of flint are common, hydrous silica is also found, and is then opaque and resemblea flint in appearance. The opal which is of value for ornamental purposes, and is sometimes called noble opal, will be dealt with under the head of gems. A substance of some value for industrial purposes, called infusorial earth or tripoli, ia also hydrous silica. It is composed of microscopic organisms called diatoms, and is used in the preparation of dynamite and also in making soluble glass.

Silicates of Magnesia and their CBrBTAi.i;.ooBAFHic Allies.

It is necessary to divide the silioateB into groups according to their chemical composition. Those first dealt with are ail silicates of magnesia, and all are hydrous. When sufficiently pure, meerschaum, talc, and steatite will give before the blowpipe, when moistened with a solution of nitrate of cobalt, a pink mass which is characteristic of magnesia.

The first three minerals in the table are sufficiently soft to be scratched by the nail j but serpentine is harder, approximating in hardness to calcite.

None of those minerals, when pure, effervesce with acid ; but if they contain an admixture of carbonate of lime, which is sometimes the case with serpentine and meerschaum, effervescence can be observed.

As regards fusibility, they are very refractory, being only fused with difficulty in small fragments and on thin edges.

Ueerflohaum, when pure, is very Ught; and, when dry, will float on water. It will be recognised by its property, when dry, of adhering to the tongue, and by its smooth, compact texture. It is generally found in serpentine, in which rock it occurs in nodular masses ; but is also in limestones of tertiary age. It is a useful substance when found in quantity, and of a snowywhite colour, being used, as everyone knows, for the manufacture of pipes.

Talo, Steatite, and Boapstone are, mineralogicalty speaking,

Amd Non-Uetallic

Bird-ne

M.

epacine

Maerehkam,

Silica, mkgneiiEi,

White, atreab

ilig; BhlDing

Earthy. Givea pink colour with cobalt aolntioa before blowpipe.

Talc, . .

Do.

Green

Pearlyorresinousi

fr."'?bi.,'"t,"t

elastic. When heated, loiea colour and emiU light, but doei not fuBO.

Do.

n

Grey,

green.

yellow

tera fusible to

white enamel.

water

yellowreddish

Becomes brownish-red when heated and loses water. Fuses at

water

H

Olive, green

edges.

ly flexible, not elaatioi fuses at edges only. Yields water when heated in glass tube.

WWte mioa.

Silic,

SUvery

alumiDa, poU.h

white

fusible or fuseB only on edges to

a grey or yellow

Black mica

glass. Lamina thin-iron

, potuh

streak, greeniab grey

lustre nacreoos on cleavage. Before blowpipe

fuses on thin edges; gives iron

LEpidolito. .

Silica, alumina,

iroii,ithU,

Pink

yellow.

bead with borax. Lustre pearly in small scales or massive. Before

ish

blowpipe colours

flame crimson.

le

S8 FBOSpnTTiiTa ros hiitebalb.

the Bftme mineral, of varying degrees of purity and in different modes of aggregation.

Talc 18 the pure crystallised mineral, occurring in transparent lamince, which can he bent, but are not elastic like mica. The colour of tolo is often a light green or pearly-white, its lustre is nacreous or greasy, &nd it is characteristically soft and soapy to the touch. Steatite or soapstoae is a massive variety of talc, and, when sufficiently homogeneous and free from cracks, it can be sawn into blocks and used as firebricks. Crushed and purified by washing, it is formed into cakes of difierent colours, and is used by tailors for marking cloth. Talc and its varietiea occur associated with serpentine, magnesian limestone, and especially with talc and ohloritia schists.

Serpentine is found in. extensive masses, sometimes forming high mountain ranges ; it also occurs in veins and beds, and is consequently to be considered as a rock of some importance. Its occurrence and distribution are, moreover, of interest, on account of the valuable mineral deposits — .g., gold, platinum, copper, nickel, and chrome-iron — frequently associated with it, and it is also the principal repository of meerschaum and soap stone.

Chlorites and MioM are remarkable as occurring generally in thin laminse easily separated one from the other, and transparent. They are all softer than calo spar, and are not easily fusible. These characters alone would not be sutfioient to distinguish them from talc, but the greasy feel of talc will serve to distinguish it easily enough in most coses ; besides which, talo is generally light green, while the most common variety of chlorite, which occurs in small grains or scales, is of a deep green colour. The micas are nsualfy white or black; their plates aro elastic, while those of talc are not.

Chlorites are hydrous silicates of magnesia, alumina, and iron, and there are varieties in which the proportions of these basis are different. In some, magnesia predominates, such as the variety called pennine ; while in the variety called ripidolite or simply oblorite, alumina is in the larger proportion, and iron. in greater quantity than magnesia. They all fuse with difficulty before the blowpipe to a grey or black slag, and when iron present in sufficient quantity this slag is magnetic. Pennine occurs in serpentine, often associated with other minerals ; ripidolite is the most common variety in chlorite schists, talcose schists, and amphibolites, being often associated with garnet, &c.

Rocks and minerals of a dark colour, usually green, are frequently associated with metalliferous deposits, especially those of copper and more rarely gold ; and chlorite is frequently met with in metalliferous districts, not only in the dark or basic rocks, but also with tin in light or acidic rocks, such as granite.

luuile

AND VOIT-lfSTAIXIC UINERALS. 59

Mioas, eBpecUllf when found in large plates, are both flexible and elastic, and this property renders mica very valuable whea it is white and can be obtained in large sheets. It ia sometimes used instead of window-glass on board ship, for stoves, and for chimDeya for lamps. Biotite, or black mica, contains more magnesia than alumina, and is sometimes called magnesian mica; it is oftenpresent in eruptive rocks, especially some granites, Muaoovite, or white mica, on the contrary, contains more alumina than msgnesia, and as it also contains potash in small but appreciable quantities it is sometimes called potash mica.

In the Trans. Inat. o/Min. and Met., Mr. A. M. Smith classifies the mica mined in India aa : — (1) Ruby mica, hard and tough; (2) white transparent mica; (3) discoloured and smoked; and (4) black mica and flawed. The prices for beat ruby are, for sheets : —

No. Sq. Id. Per lb. No. Sq. ia. Perlb.

a) 36 to 50 . 6/8 I (4) 10 to 16 . 1/- (8) 24 to 30 . 4/' (5) to 10 . /4

Special sheets of over 50 sq. ins. bring as much as £1 per lb., according to size of sheets. The white mica is worth about onehalf, discoloared one-quarter, and flawed oue-eighth the price of ruby.

Muscovite is an important mineral to the tin miner, since it is always found in stanniferous granite, and with quartz it forms greisen, which ia very generally associated with tin. Granite with large sheets of mica is sometimes called pegmatite. Muscovite also forms an essential part of other light coloured acidic rocks, such as gneiss and mica schist, and is sometimes found as an accessory in granular limestone and some volcanic rocks, such as trachyte and basalt, but only as an accessory mineral. The small scales in sedimentary rocks are probably of granitic origin.

Iiepidolite, or lithia mica, is a variety of muscovite containing practically no magnesia, and characterised by the presence of lithia, an alkali which is of value on account of its medicinal properties. Lithia mica will be readily recognised before the blowpipe, as it imparts a beautiful crimson colour to the flame, especially if powdered and mixed with a little fluor spar. It generally occurs in scaly granular masses in granite and gneiss, and is sometimes associated with limestone and tonrmaline. It is very abundant in Bohemia; but the moat plentiful supply of lithia is derived from a mineral spring in Oomwall; and it is probable that the lithia in this water is derived from the tin granites of the country. Lithia mica is associated with tin granites in Bohemia, Sa:cony, and France.

For Ii In Bb Alb.

(OryjioHin* Rock-forming Minerals.)

Hud

Bpecifli

Colour

Orarttj

Kemarta.

Silica, alumiuB potaah

ColonrlMi, white, pink,

W bite or pale

Fosible to bubbly glass, blowpipe

Albito, .

SUioa,iilaiiiiiiB

rescUaDfbrpoUsb. Fusible to bubbly

Bocu

glass.

Silica,aliimiiia,

White, greyUh

Fuaible.

soda, time

Labradorita,

Mors emily fuiibte.

time, Boda

yellow, with coloured plays of light

easily attached by acid*.

Anortliite. .

Do,

lime

wyte '

Silica, magne-

White or pale

FnaibU with ebulsia

, Ume

green

lition to white

glass.

Aclinolite, .

Silic*, magne-

Green, streak

Fusible to a grey-sia

, lime, aad

little iron

white

w

Silica, m§ne. sia, lime, iron

Bi

Black or deep green

Fasible to greyish or glass.

SUica, lime, magnesia

ColourlsBB, white-green

Fuaible to white or greyish glass.

Dialkge, .

Silica, lime.

3S

Grey, greenish,

fusible to a grey

s

mttgnesia

brownish

or green glass.

u

Silica, lime.

BUck or deep

Fusible to a black

green

magnetic glass.

Augit.. .

Silica,' lime.

Black, deep green, generally opaque

Fusible to a black often magnetic glass.

Bnstatite, .

Silica, magne-

Greyish, white Brown , yellow-

Nearly infusible.

Brontlte, .

Silica, magnesia

Nearly infusible.

and liUU Iroa

Hypenthene,

Silica, magne- WB, iron

Greenish or brown-black.

Fusible to a black magnetic glass.

copper - red

SiUca, lime

colour?

Fnsible with difficulty.

EOCK-FOBKtNa AND NON-UBTALLIC HINBBALS. 61

There are several magnesian minerals which have received different names, bat are really only varieties of serpentine ; they are generally coloured green by the presence of a little iron or sometimes nickel. They generally occur in serpentine formations, and the deep green varieties are often associated with the silicated nickel ores.

The minerals of this group are of great importance in formingrocks, especially the eruptive; but topaz, tourmaline, olivine, epidote, and garnet, which less often play an essential part ia the constitution of rocks, are included with the gems.

All minerals included in this group are anhydrous silicates and may be subdivided as follows : —

1. Felspars, including orthoclase,albite,oligoclase,labradorite, and anorthite, which are silicates of alumina and other oxides.

2. Hornblendes, including tremolite, actinolite, and hornblende, which are silicates of magnesia, lime, and other oxides.

3. Augltes, including diopside, diallage, hedenbergite, and augite, which are of similar composition to the hornblendes, with different proportions, however, of the component substances.

4. Enstatite, bronsite and hTpersthene ; the first is a silicate of magnesia; the last two are silicates of magnesia and iron.

For the composition of the eruptive rocks, see the table on p. OrthooloSd. — If a piece of granite be taken and a variety composed of Urge crystals chosen, it will be found that, besides the scales of black or white mica, grains of quartz will be easily recognised by their transparency, irregular shape, and hardness ; whilst the rest of the rock will be found to consist of a white, greyish, or pink mineral, scarcely transparent, and breaking easily in two directions, on one of the faces of which the mineral, exhibits a nacreous lustre. If the facets produced by the fracture are large enough it will be seen that the two are at right angles to one another. This mineral is orthoalase, the most common and moat important of all the felspars. It is alsocalled potash felspar, and it is this mineral principally which, by its decomposition, forms deposits of kaolin or clay, the potash being dissolved. In some lavas it is stated to form an amorphous, paste, whilst some well-formed crystals of orthoclaae can also be detected ; and it is also one of the component minerals of gneiss and many crystalline schists. These are all rocks, in the formation of which water, at a considerable temperature and underpressure, has taken a prominent part.

S2 PROSPEOnSO FOB HINEBALB.

If, on the other hand, & specimea of trachyte be taken in whitish large crystals are developed, it will be found that crystals occur, which like orthoclaae in granite, have two cleavieB at right angles to one another, but a casual examination of these orratals will further show that they are transparent and vitreous. This constitutes another variety of orthoclase, known as sanlne. It characterises rocks, such aa trachyte in the formation of hich heat has played an important part, which have, in fact come to the surface in a state of fusion. Not only is the ortho- -clase in these rocks different in physical aspect from that of granite, but, as already pointed out, the <]uart is sometimes replaced by tridymite, the specific gravity of which — viz., 22 — is that of fused quartz.

Orthoclase, as wall as the other felspars, is fusible before the blowpipe ; so that a light-coloured granular or compact rock which is fusible in small iragmentB is most probably composed of felspar, and generally orthoclase. Some of the fusible rocks are granular or compact, but still of eruptive origin — e.g., euriU; some are vitreous and compact — e.g., obsidian — a black rock which is also called volcanic glass ; and some are vitreous and porous — e.g., pumiee — in which the porous state has been produced by steam evolved in the interior of the molten mass. These are all of volcanic origin, but there are also rocks composed of very minute, even microscopic, grains of felspar which are truly sedimentary rocks, and are termed euritinea. Orchoolase is used in the manufacture of porcelain and enamels.

Albite is a felspar, resembling orthoclase, in which soda replaces the potash. It is generally white, and occurs in some ]>articular varieties of granite porphyry, diorite, gneiss, crystalline schists, &o. It is a rare mineral compared with orthoclase as a constituent of rocks, but some granites contain it as an accessory mineral ; and it is also found forming veins in ordinary granite, being frequently the matrix in which the rarer associated minerals, such as beryl, tourmaline, &a., are imbedded.

Oligoolasd is like albite, but contains a little lime. It generally occurs in laminar masses or crystals in the same rocks in which albite is found ; its colour is generally white, greyish, eenish, or green. This mineral possesses an easier cleavage than the other felspars, and characteristic parallel stria can be seen on the cleavage planes. The varieties of felspar which are used as ornamental stones, and are called sunstone and moonfltnne, are pure orthoclase or oligoclase with enclosed flecks of reflecting material.

lAbradorite, like oligoclase, is rarely found in crystals, but

BOCK-FORHinO AND SOH-UETALLIC HINEBALB. 63

in deftvable laminftr masses, the cleavage faces being striated. It ia grey, white, yellow, ifcc., and on certain faces often exhibits a remarkable play of colours, such as blue, yellow, green, red, fiery, or aemi-metallic. In this felspar lime is an important constituent, and there ia also a smolL proportion of soda. It is more easily fasible than the other felspars, except oligoclase, and is in great part solnble in acids. It constitutes an important element in the basalts, but often occurs in such small crystals that it can scarcely be seen with the naked eye. An iridescent variety is found on the coaat of Labrador in large masaes, and forma a. yaloable ornamental stone.

Anorthite ia a rarer species of felspar. It occurs in small white or colourless crysUJs resembling albite in shape, ia almost entirely a lime felspar, and is easily fusible, although not so easily as labradorite ; it is also attacked by hydrochloric acid. It occurs in granite, gabbro, serpentine, and many volcanic rocks.

Tlie hornblende group includes three principal varieties in which the colour varies in proportion to the increasing percentage of iron present. Tremolite, containing little or no iron, ia white; aotinolite, containing a few units per cent, of iron, is green ; and homblende, containing iron, ia black. They are in consequence sometimes called white, green, and black hornblende. They are all fusible with ebullition before the blowpipe, the first forming a white, the second a grey, and the last a black bead.

The most common form in eruptive and metamorphic rocks is hornblende, the black variety, which occurs as a constituent of fiyenite, diorite, hornblende -andesite, hornblende-schist, itc., ;generally in the form of flattened prisms. It ia also associated "With angite in some modern volcanic rocks.

Aotinolite occurs mostly in hornblende-schists, where it is -frequently in the form of slender needle-shaped or flat prisms. These hornblende-bearing rocks, it may be remarked, are often connected with metalUferoos deposits.

Tremolite is of less importance as an element of rocks, but is interesting in other respects. It is more rarely found in well formed crystals than the two other varieties, but is often in baccillary or radiated fibrous masses, forming the well-known .-substance called asbeBtos when pure and in long flexible filaments, and mountain leather, ic, when of inferior quality. In the compact state, when its crystalline structure can hardly be detected, tremolite forms a very tough and valuable substance known as jade or nephrite, which varies in colour from white te green, and is found in Obina, Mexico, and New

Zealand. The Chinese images are well known ; the hard ones are made from jade, and those which are soft from other minerals cloaely allied to steatite. The Mexican and New Zealand jades are well represented ia most collections by stone axes, arrow heads, izo.

It may be added, to avoid confusion, that one of the minerals used by the Chinese, and known ss jatU, is not compact tremolite, but a compact variety of white epidote called xoisite.

The angite miaerala form a nearly parallel group to those of which hornblende is a type, and differ from them principally in the angles of the crystals. The varieties of the augite group are as follows : —

Dlopaide is a transparent, colourless, or light green mineral which occurs in serpentine and granular limestone, but is comparatively rare. It is not a rock-forming mineral, but occurs in veins, and is a silicate of lime and magnesia, with, occasionally, traces of oxide of iron. In the blowpipe flame it ia fusible to a white or greyish glass.

DiallagG, which is of greater impoi'tance as a rock-forming mineral, is a variety of augite. It occurs as an element of some varieties of serpentine, and in the important rock called gabbrc which often accompanies serpentine. It contains more iron than diopside, besides a little alumina, and is easily fusible before the blowpipe to a grey or green bead. It is found in laminar masses, and has generally a nacreous ox semi-metallic lustre on the principal cleavage face, and in colour is grey, green, or brown.

Hedenbergite is a black lamellar variety of augite containing much iron, manganese, and zinc, besides lime, and is fusible to a black magnetic bead It is found in some cavities and veins in the older formations, and has no importance as a component mineral of rocks.

Augite is the best known, and most important mineral of this group. It occurs generally in well-formed black crystals, sometimes difficult to distinguish from hornblende, but in the prisni of augite the angles of the primitive faces are about 87° and 93°, thus approaching a rectangular prism, whilst in hornblende they are about 124° and 56°, the section of the hornblende prism thus forming a more oblique rhomboidal figure than augite. In jufSciently large crystals these angles can also be obtained by cleavage, as the easy cleavages in both groups are parallel to the feces of the prisms. Another character by which crystals of augite may sometimes be distinguished from hornblende is the brilliant lustre of augite compared with the dull lustre of hornblende.

BOCK-roBHIBO AKD NON-MBTALLIO UKER&LS. 6S

Augite contains lime, magnesia, iron, &o., and ia fumble to & black glass, which is often mogaetio. It is common in the volcanic lavas, where it ma; be seen ia the samd specimen as a constituent of the paste in mioroscopio grains, and in well-formed crystals.

Enatatlte is very closely related to augite, having nearly the same crystalline form, but belongs to the rhombic system. It ia a silicate of magnesia, and, except for its associations, would be more properly included in the preceding group. It is practically infusible or fusible with difficulty on the edges of very Hmall scales. It occurs in some andesites and serpentines, and in the rock called Iherzolite.

Bronzite is a variety of enstatite, and is isomorpbous with it. It occurs in some serpentines, where it has a lamellar structure, and exhibits a nacreous semi-metallic lustre on the face of easy cleavage. Its colour is brown, pale brown, or greenish-yellow, and it fuses with very great difficulty, like enstatite.

Hypersthene is also isomorpbous with enstatite, but contains as much oxide of iron as magnesia. It is a dark laminar mineral, characterised by a reddish-brown colour, with a capreons lustre on the cleavage planes. It is fusible to a black magaetic bead, and helps to form the eruptive rock called hypersthenite.

Wollastonlte ia a silicate of lime, and is a white mineral, rarely crystallised, possessing a nacreous lustre, and occurring ordinarily in lamellar or bacillar masses in granular limestone, grtuiite, or basalt. In some cases it is associated with silver and copper ores, and frequently with garnet. It is fusible with difficulty before the blowpipe.

Htdbous Silicates of Lihx and Alumina with tqiib Allies-

The Zeolites form a highly interesting group of beautifully crystallised minerals, occurring, in the majority of casea, in cavities or fissures in volcanic rocks, but as they are of no economic importance and are seldom found in mineral veins, much apace will not be devoted to their description.

Zeolites are bydroua silioates of alumina with other oxides, usually alkalies, and their specific gravity ranges from 21 to 2-9. The softest is scratched by fluor spar, and scratches calcite ; the hardest is prehnite, with a hardness between orthoclase and quartz. They are usually colourless or white, or of a very pale pink grey or green, as they contain little or no iron. Even in the darkest of all, a brick-red variety of bealandite, the colour is attributed not to iron, mixtoCftof another mineraL

66 PBOSPSOIISO FOB HltrBBALB.

Frelmite, which is uaually pale green, ooatoina a, smEtU percentage of protoxide of iron. All zeolites melt and swell up when heated before the blowpipe.

HYDROUS SILICATES OP LIME AND ALUMINA WITH THEIR ALLIES. {ZeoliUt—OryitaliUed Mineralt (if Secondary Origin.)

Uiuenili.

Componenta.

aiadtr'

Strukud

Bemsilu.

Hmlandite, .

Silic*, aln-

3B-4

White to

Fusible with intu-brick

-

meeoence, soluble

water

red,

streak

white

in acids without gelstinising.

Silica, aln-

WMte to

Fuses to white

miM, lime.

brown

enamel.

Apophyllite,.

Silicft. lime.

4&#x27;B-5

White to

Exfoliates andfuses

grey or

to white enamel.

Fed

potash flame.

3iHea, aln-

White,

mino, lime.

White,

acid.

water

Qehitinises with

N&trolit, .

Silica, alu-

S-0-5-6

acid, fusible In

mina, Boda,

yellowish

oandle flame.

water

Silica, alu-

B-B

White to

Fuses very easily to white enamel.

mina, lime.

brown

Hoda, water

icid.

HMmotome,.

Silica, alu.

WMte or

Fuses without in-mina

, baryta,

grey

water

ble without gela- Untsbg.

Silica, aln-

S-5-B

White,

Fuses quietly to

mina, soda,

greenish,

glass, geUt&ise.

reddish

with acid.

Silica, aln-

White to

In rhombohedrons ;

mina, lime.

reddish

whitens before Fuses with intn-

Prehnite, .

Silica, alu-

a-6-e

Pale

mina, lime,

green

water

in acids without radiate groups.

Some zeolites are fotind in gneiss — e.g., heulandite, laumonite bBTEBotome or cross stone, and prehiiite, Harmotome and

HOK-METAtLIO UIMEBAL8. 67

betlliuidite have been found in tlie silver mines of Andreasberg; analoime in the amygdaloida at the copper mines of Lake Superior ; and prehnite ocoura, not only in the above copper mines, but also, in New South Wales, with orthodase and copper ores at Beedy Greek, County Mnrchison. ,PreImit6 is certainly, of all the zeolites, the most interesting in consequence of its associations. It is further mentioned as occurring in crystalline rocks and especially in diorite and other hornblende rooks, from the decomposition of which mineral it ia probably derived.

Basalts and lavas containing abundance of zeolites may sometimes be utilised in the arts when, in consequence of the quantity of alkalies present, they are so fusible that they may be easily melted and cast into different forms.

Chabazlte is the most common of the zeolites found in basalts.

Basaltic lavas, especially when they are in the state of sand a contain a sufficient proportion of alkalies, are used as puzzuolana in the manufacture of cement.

NON-CBTBTALLIirB SILICATES OF ALUUINA.

ClB. — The clays are all prodacta of alteration lirom other minerals, their composition is variable, and they do not crystallise. The true clays are all plastic and refractory to a greater or less degree, and on these properties their value for industrial purposes depend. Pure kaolin is the type of all the clays.

Suoh hard earthy minerals as allophane and halloysite may be termed, by analogy, hard clays, since their composition is generally similar to some of the soft plastic clays ; but they have not yet been used for msnu&cturing purposes. They are not plastic, ont are derived, in some cases at least, from the decomposition of fetspathic rocks, and are often found in mineral deposits.

The presence of alkalies in clay is objectionable, as it renders them fusible, as also do many other oxides. Iron is not only objectionable on the score of fusibility, but also as a colouring matter. The presence of too large a proportion of water, carbonic acid, or organic matter causes clay to contract under the action of fire, and the same result will ensue if the clay is partially fusible. Contraction may also arise from the mechanical arrangement of the particles, and of two clays having the same chemical composition, both of which contain a certain percentage of free silica, the finer one will contract more than the coarser, in which the particles are preserved from that close contact which is necessary for their ready combination and fusion.

The soft clays are divided into kaolin or poroelain olay,

6S PBOSPBcnira fob hihebals.

which is nearly pure, and is derived from the decomposition of felspar in pegmatite or granite ; plaatio or pottery Olay, not so pure oe kaolin ; and bole, containing a great percentage of oxide of iron. Fnller'a earth is a kind of clay uaed for freeing wool from &tty matters. It is not easily mode into a paste with water, and its application is therefore limited to the above purpose, for which it is of great value.

Ohapteb Iv.

Pbk0I0U8 Stones And Oems.

Thb minerals which are used for ornamental purposes are mostly of considerable hardness, and capable of receiving a high polish. They yary greatly in their chemical composition, but are best divided by their hardneaB into two groups, viz., those which are harder than quartz, and those which are not harder than

Hakdib than Quartz.

Diamond is pare carbon. Its hardnesi, specific gravity, and peculiar lustre, due to its high refractive power, have been already referred to. It will be readily recognised by the prospector who has onoe seen it in the rough, if simple tests are applied, for diamond will scratch sapphire. The gem prospector should always carry with him some pieces of sapphire, topaz, and rock crystal, as well as a diamond.

In ite natural repositoriee, diamond is not always readily recognised by its brilliancy, and it is often encrusted with a black coating, or cemented with ironstone ; but its greater weight will cauae it to settle to the bottom of a tin dish or sieve when washed with other non-metallic minerals of the same size ; and if the dish or sieve be turned over suddenly, the diamonds will remain on the top of the heap, which should be carefully picked over.

Dana says {Sytem of Mineralogy, 5th edition) — "The diamond appears generally to occur in regions that afford a laminated granular quartz rock called itaeotvmiie, which pertains to the talcose series, and which in thin slabs is more or less flexible. This rock is found at the mines of Brazil and the TTrala, and also in Georgia and North Carolina, where a few diamonds bava been found. It has also been detected in a species of conglomerate

PBECIOCS STOKES AND OBHS. b9

composed of rounded siliceous pebbles of quartz, chaloedon;, &c, cemented by a kind of ferruginoos clay,"

In some of the scbiatose rocks of Brazil, above alluded to, it is admitted that the diamond exists in siia, or in the rock in which it was formed; and M. Gorceix states that these rocks are traversed bj veins of quartz with rutile, tetrahedrite, oligiste, and martite, the two last being varieties of htematlte.

In the Kimberley district, 8. Africa, the parent rock of the diamond is a kind of serpentine, which forms huge dykes or necks of igneous rock which have come to the surface, but have not apparently overflowed the lip of the vent or crater, and, according to Mr. Dunn, a geologist at the Cape who baa devoted much time to the study of the diamond and gold deposits of this part of the world, these so-called "pans" are local depressions in the flate, and are sometimes as much as three miles in length. He also states that when the eruptive rock has been removed the walls of the cavity exhibit horizontal beds of shale, their edges being turned up along the line of contact with the eruptive rocks. The upper bods are, in some instances, formed of grey, pink, or yellow shales with fossil remains (Saurians) ; the lower beds, from 60 to 150 feet thick, consist of black carbonaceous shales. So combustible are these shales, that when accidentally ignited they have been known to bum for over eighteen months. In this serpentine diamonds are generally found crystallised in octahedra and some of the allied forms.

In Borneo diamonds are said to occur in a matrix of serpentine, and In New South Wales and at Beechworth, in Victoria, good diamonds, although small, are found in alluvial deposits in great numbers. Some of these deposits have of late years received a good deal of attention, and may eventually prove of considerable value. Diamonds have also been worked in alluvial deposits on the Yaal Kiver in South Africa, at Golconda in India, and other places; indeed, with the exceptionof the mines of the Kimberley district, in which the stones occur in sitli in serpentine, all the important diamond fields of the world have been tluvial deposits.

The occurrence of diamonds of different colours affords a remarkable illustration of what has been said about the colours of minerals. As pure carbon, diamond is colourless, as also are the microaco[)ic diamonds artificially produced by an electric current; but in nature the stones are of different colours, wliich are imparted to them by a very small proportion of foreign matter.

The yellow and grey tints decrease the value of the diamond;

bnt red, blue, and green varieties, on the contrary, are ao rare, that when diamondB are ao coloured their volae is conBiderably greater than if perfectly colourless. For inatacoe, the best blue diamond known (44 carats) is estimated at double the calculated value of a good colourless diamond of the same size, viz., £30,000.

In Borneo a kind of black diamond ia found which is very highly prized in consequence of its exceptional lustre and rarity; it is even harder than the ordinary diamond.

In Brazil another variety of black diamond, called "bort," which is rough and without lustre, and somewhat resembles the deposit of gas retorts in appearance, is found in quantity, and ia used for diamond drills. It sometimea occurs in masses as much as 8 oza. in weight, and is as hard as the ordinary diamond.

Octahedrite, a mineral occasionally found with diamond, is mentioned under rutile, and is sometimes so splendent as to be mistaken for diamond itself. Diamond should also be compared with white zircon, the lustre of which is also adamantine.

Xhe diamond always occurs as a constituent of rocks or in alluvial deposits and never in lodes. It is principally valued on account of its hardness and high refractive power, being the most valuable ornamental stone. It ia also largely used in rock boring drills ; and diamond dust is of importance for polishing purposes.

CoTUodum (sapphire, ruby, &c.). — A. number of hard atones of various colours and known by different names belong to this mineral species ; they are all essentially composed of alumina. The most common of these gems is blue eorundtim or sapphire, which is very frequently found associated with alluvial gold in Australia.

Green varieties, called Oriental emeralds, also occur with sapphires, sometimes in considerable numbers, but seldom of a good colour, the moat common tint beiig that of water worn bottle glass which may be so often seen on the sea shore. When pure, and of an emerald colour, they are of a great value, both on account of their hardness and rarity.

Yellow corundum is called Oriental iopax, and, being harder than topaz itself while of the same colour, has a greater value. The violet variety is called Oriental amethyst and is not

Bed corundum or rviii/ is next to diamond in value; indeed, a ruby of 3i carats when perfect is even more valuable than a diamond of the same size. A ruby of 4 to 6 carats in weight ia

Pbeoious 8T0Neb Asd Geus. 71

a great rarity and ia worth forty or fifty times as mach as the best sapphire of the same weight.

Black corundum ia often met with ; like emery (which is only an impure variety containing more iron), it ia useful for cutting and polishing stones of less hardness than itself. Emery, which is largely used for polishing purposes and for the manufacture of emery wheels (now ao largely used in machinery works), is the coarsest and commonest variety of corundum ; it contains from 10 to 60 per cent, of magnetite and its abrasive power is about half that of sapphire. Most of the emery of commerce comes from K'axos or Asia Minor, It is found in Asia Minor near the Bur&ce like a bed of conglomerate resting upon limestone, and it is roughly hand picked on the mines. It is minedby blasting, the bore holes being made in the joints of the rock which are frequently filled with oaloite ; sometimes also it is worked by firesetting, although this is said to deteriorate the quality.

The fine varieties of corundum have been chiefly obtained from alluvial deposits ; they have rarely been traced to their parent rock and have never yet been found in a matrix from which it would pay to extract them, as is the case with the diamond in the Eimberley district and the emerald in £eru. In parts of New South Wales, corundum is said to Occur &i basalt with olivine; in alluvial deposits it ia found with other hard stones and with tin, gold, ho.

The hardness of this mineral, which is next to diamond, should make it easy always to distinguish ; so far as the sapphire is concerned the colour is quite distinctive. Numerous mistakes, however, have been made about the ruby, and it is no uncommon thing for zircon and garnet to be mistaken for it, notwithstanding the easy means of discrimination afforded by the respective hardness of the difierent minerals.

Dana says (System of Mineralogy, 6th edition) — "Corundum is associated with cryatalline rocka, as granular limestone, or dolomite, gneiss, granite, mica alate, chlorite slate." A species of felspar with oblique cleavages, called anorthite or indianite, ia said to be the gangue of corundum in the Carnatic, India, with garnet, oyanite, and hornblende. At Barsowski in Russia a granular variety of anorthite is said to occur in the auriferons sand as the gangue of tdie sapphire.

ChiTBoberyl comes next in hardness to corundum. It ia not transparent, but translucent, and exhibits a play of colours in different shades of green, like a cat's-eye ; sometimes a bluish opalescence is to be seen internally.

In alluvial deposits it occors as rolled pebbles, and in tlie Ural mountains is found in sUil, in peculiar star-like groups of crystals, in mica slate associated with beryl and phenakiw. It is composed of alumina and glucina.

Spinel is an alumiuate of magnesia, and includes several varieties, of which the red variety, spinel niby, ia generally meant when spinel ia spoken of as a gem. A variety, which contains a fiur proportion of iron and is sometimes called black spinel, is referred to under the name of pleonaste as a stone often found with alluvial tin.

Spinel rubiee generally have a dull bluish tinge, which places them &r below the true ruby ia point of value ; they can readily be distinguished by their lesser hardness even when in colour they rival the more valuable gem.

Green and blue varieties of spinel also occur. The blut variety is very inferior to the sapphire, even when of very good colour ; and green spinel is more a curiosity than a gem. It occurs in octahedra when not waterworn.

.Red gpinelt are sometimes found in alluvial deposits with gold, but they are generally very small ; and they have occasionally been found in sandstone, but were probably derived from igneous rocks. They are also said to occur imbedded in granular limestone and with calcite in serpentine, gneiss, and allied rocks, as also in cavities in volcanic rocks.

Topaz is a silicate of alumina with fluorine; and its hardness is little less than that of spinel ruby.

Whiu topax is common as waterworn pebbles in alluvial deposits associated with gold, and has an easy and characteristic cleavage parallel to the base of the prism. It is sometimes sufficiently brilliant to be valued as a gem, especially when well cat; but it is not to be compared with a well cut diamond.

Theyofe blue variety is of value for cutting into large stones for brooches ; specimens are occasionally found of several pounds weight.

Topaz of a beautiful sherry colour occurs in BraziL Specimens of this, when heated, become pink, when they are known as burnt topaz. A lighter coloured variety is found in the tin mines of Saxony, and is said to have been found in Tasmania.

The yellow varieties are cut as gems; although not very valuable they have considerable brilliance and look very well.

Emerald and Beryl are chemically the same, being composed of silica, alumina, and glucina.

The varieties known as beryl are generally opaque or nearly so, and are light green or yellowish in colour. Large crystals, six-

Fbbci0U8 Btokes And Gems. 73

sided prisma, are common in veins of pegmatite traTersiag granite, and are also found imbedded lb quartz.

A pale greea or light blue transparent variety is known as aqwvmwriae, and is sometimes used as a gem, but bas no great value. It ia sometimes mistaken for topaz, but is neither so hard nor so heavy ; nor does it, like topaz, become electric by friction.

According to lapidaries, enumld is a little softer than beryl, but its rich and characteristic green colour makes it a gem of great value. It is found in mica schists in Siberia and Salzburg ; and in clay slate with concretions containing Oretaoeous fossils in Granada. The emeralds &om the last locality are especially noted for theit beauty of colour, but the largest crystals have been obttuned from Siberia. Some emeralds have been found in a vein traversing granite in 2few South Wales, and minute specimens in a syenitic gneiss at Dusky Sound, Iew Zealand.

Phenakite differs from emerald in composition by not containing alumina nor the traces of green colouring matter. It is generally colourless, but rarely wine yellow, so that it is difficult to distinguish from topaz, their hardness being also the same. Phenakite is, however, lighter and considerably rarer, It occurs in the Ural in mica schists with chrysoberyl and emerald ; and elsewhere, associated with other minerals.

Zircon is a silicate of zirconia. The crystals are of various shades from colourless and transparent, when they are sometimes mistaken for diamonds, to yellowish, green, brown, and red. The smoky white varieties are known as jargons, the transjiarent red varieties as hyaeirOht, and the grey and brown forms as zircons.

This mineral is remarkable for its brilliant lustre, which approaches that of the diamond, but it is not of much value. It has been found in granite and other crystalline rocks, and occasionally in volcanic rocks.

Dichroite or Cordierlte is a silicate of alumina, iron, and magnesia. It is not commonly used as a gem ; it is of more value as a curiosity, in consequence of its showing two different colours when light is passed through it from different directions, than on account of its real beauty. It has been named dichroiU from this property.

It exhibits various shades of blue in one direction, and a brownish-yellow or yellowish-grey in a direction at right angles to the first. It is known to jewellers as "sapphire d'eau." It occurs in granite, gneiss, hornblende, chlorite, and talcose schists, snd allied rocks, with quartz, orthoolase, albite, tourmaline,

hornblende, ondalasite, and, sometimea, beryl It is also found in Tolcanio rooks, and is often decomposed.

Tourmoliiie will be mentioned as a mineral accomp&n jing tin. There is a remarkable instance of it occurrence with gold in the New Mount Morgan mine in Western Australia, where gold is commonly disseminated through the joints of the crystals, it is a boro-silicate of alumina and other oxides, and contains fluorine.

There are many varieties, but those used as gems are either red, green, or blue. The first is termed vtAellita by mineralogists, or simply towrmaiine by jewellerB ; the green and blue varieties are known as Brasilian emerald and sapphire respectively, and in Brazil they are worn by dignitaries of the church.

Tourmaline is usually found in granite, syenite, gneiss, mica schist, chlorite schist, or talcose schist, as also in diorite, dolomite, granular limestone, &c The most common variety, schorl, is black. It is easily recognised, as it occurs in long needle-shaped crystals, which become electric when heated.

Gamdt is also alluded to as a mineral which often accompanies tinstone, or is likely to be mistaken for it ; only those varieties used as gems will be mentioned here. The colour is blood-or cherry-red, passing to various shades of crimson, purple, and reddish-violet on the one hand, and to orange, red, and hyacinth-brown on the other.

Unlike other red stones, garnet is not readily out in faoea, and ia generally cut as carbuncles or, in other words, with a smooth oval surface. In this form the best qualities display brilliant fire-red flashes of light. The best garnets used as gems belong to the varieties called almandtne and pi/rope; they are chiefly obtained from Syria and Bohemia, and are called in the trade "Syrian" and "Bohemian garnets."

Besides the red-coloured pyrope and almandine, there are some other varieties of very diflerent colours. A green garnet, called ouvxtroviile, is coloured by oxide of chromium ; a black garnet found in crystalline schists is called melamte, and contains much iron.

Not Hardeb thar Quartz

There are many varieties of quartz which claim some attention as ornamental atones, all of which consist of silica.

Book Crystal occurs crystallised in six-sided prisms with pyramidal ends ; it is perfectly clear and transparent, and is used both for optical instruments and for ornamental purposes.

PBXOIOtta BTOMES AMD OBHB. 75

It is sometimeB found m crystals of enormoas size, several weighing from 8 to 10 cwta. having been recorded; and it is reported that about a century ago a druay cavity was opened at Zinken from which 60 tons of rock crystal were obtained, which realised X60,000.

Smoky quarts, or Caimgorm, has a smoky yellow to brown tinge. The colour ie probably due to titanic acid, as orystaU containing rutile are generally smoky. It is called eaimgorm. from the locality in Scotland of that name.

Citrine quErtE, or False Topaz, which ie yellow in colour, is easily distinguished from topaz, which it resembles, by the absence of cleavage and the difference in hardness.

Amethyst quarts is the most highly valued of the coloured varieties. It may be described as clear and of a purple or violet colour. It is usually found in cavities in volcanic rocks.

Choedony generally occurs in stalactitic or concretionary masses, and is usually whitish, yellowish, or yellowish-brown, rarely pore white. This variety, in common with those which follow, is translucent.

Agate is a variegated chalcedony alternating with bands of quartz, in which the colours are cloudy or banded, but rather dull and not showing any sharp contrast one with the either.

Onyx differs from agate in being distinctly banded in wellcontrasted shades, such as black and white, or brown and white, but most of the black varieties are artificially stained.

Sardonyx is a brownish-red or orange variety of agate.

For agate to become an important article of trade it must bo found in large quantities, and in rocks so much decomposed that the process of extraction would be an easy one. Agates are mostly found in cavities in volcanic rook, where they have been deposited by water.

Cameliau is of a clear blood-red or light-red colour, but this colour is said to be produced in India by burning, it being due to oxide of iron.

ChryBoprase is of a beautiful apple-green colour, due to oxide of nickel In a warm, dry place the colour of chrysoprase is destroyed, but it can be again restored by keeping it damp.

Plasma is an olive-green chalcedony.

Heliotrope or Bloodstone is plasma traversed by small veins or specks of red jasper.

Under the names of agate and dendrites agate are included those varieties in which dendritic crystals of metallio oxides occur, a common mode of crystallisation for oxide of manganese.

Most apecimenB of petrified wood, when there is no earthy or clayey matter present, are transformed into chalcedony.

Gat's Eye is another translucent variety of quartz, but, unlike chalcedony, it is crystalline, but not amorphous. A variety containing fibres of asbestos is sometimes incorrectly called " crocidolite." It is yellow iah-green in colour, with golden and green streaks of light, and has a silky appearance, due to the fibres of asbestos. The original fibrous crocidolite is of a fine blue colour. This stone is well known as occurrintr in the diamond districts of South Africa, and is also found in Germany, Ceylon, and elsewhere.

Opal is silica in an amorphoua condition, usually with some water, and includes not only noble opal, but also those common varieties which are of no value. Fossil wood often consists of hydrous silica.

The opal used as a precious stone is translucent, and has a beautiful play of different fire-like colours — red, yellow, green, and blue being conspicuous in some varieties ; while in others, one of these colours is prominent, the rest being less distinct.

Perfect opals are very valuable, but their value is greatly enhanced when they are set, since the operation of cutting is very difficult, in consequence of their hrittleneas. They are usually found in cavities in amygdaloidal rhyolite and some other lavas.

Orthoclase, Oligoolase, and Iiabradorite. — Some varieties of orthoclase and oligoclase contain minute flakes of other material, are iridescent and exhibit a beautiful play of colours. They are called guntUme and tnoonstone, and are occasionally set in brooches, but are too soft for rings. They are chiefly obtwned from India, America, and Ceylon.

Iridescent Ltdtradorile, which is chiefly obtained from the coast of I/labrador, is sometimes found in blocks of large size and of varying colours— violet, blue, &c. It is used for decorating artistic furniture, and is sometimes cut for pins, &c.

A beautiful variety of orthoclaae known as Amazon stone occurs as large green crystals in Siberia and the United States. It would form a pretty ornamental stone, hut is not transparent.

Olivine or Chrysolite, which ia also known as peridot, is a silicate of magnesia coloured with a small proportion of iron; its usual colour is bottle green of various shades. It is not so hard as quartz and but little harder than glass, besides which it is brittle and therefore of very little value. It is an essential constituent of basalt, and occurs in serpentine. In New Zealand and New Caledonia it forms a massive rock, which frequently contains chromite, and has been named dunite.

Precious Bt0Ni9 And Obhs. 77

Epidote is a silicate of alumina and lime, with small proportions of iron and water. It occurs crystallised in loog prisms of aa olive-green colourin one direction and yellow or brown in another; so that, like cordierite, it ia dichroic It is more a curious than a precious stone; its lustre ia vitreous, and it iatoo dork for ornamental purposes. It is of common occurrence in many crystalline rocka, especially those which are homblendic, and in serpentine ; and it oiten accompanies beds of magnetite and heematite.

Eyanite is a silicate of alumina, generally of a light blue colour, but also white, grey, or green. It occurs in long, thin, blade-like crystals imbedded in mica schists and gneiss. It is of no value as a precious stne.

VeauTionite or idocrase is a complex silicate of alumina and other oxides, and is allied to garnet, but crystaUiaes in different forms ; it resembles tinstone, from which, however, it can beeasily distinguished by its fusibility. It has a vitreous lustreand a hardness of 6'5, but is of no value as a gem. It is found in volcanic rocks at Yesuvius and in crystalline schists and gneiss in many locaKtiea

AndaluBlta has the same composition as kyanite, but crystallises in different forms, besides having, when coloured, a reddish tinge. The variety chiattoUle occurs as small white rod-like crystals imbedded in slate, and exhibits the form of a dark cross due to impurities in its sections. It is a little harder than quartz, and its lustre is vitreous.

Turquoise Is a hydrous phosphate of alumina. It is amor~ pious and opaque. The best quality, the Persian turquoise, is of a beautiful sky blue colour. Odontolite, called by jewellers, "turquoise of newtock," is fossil hone, coloured by copper. It is of far inferior quality to the true turquoise, and is easily decomposed ; when the unpolished surface is carefully examined the structure of bone can be seen. Odontolite occurs chiefly in cave deposits; while true turquoise is found in sandstones, where it is found in seed-like groups.

Ultramaxiiis or Iiapis Ijazuli. — This beautiful stone is blue ; opaque or semi-translucent; and is often traversed by veins of pyrites. It ia a very complex mineral chemically (if, indeed, it must not be regarded as a rock), consisting of silicate of alumina, with soda, lime, sulphur, chlorine, &c. So long as the pigment which bears its name was obtained solely from this source, the price of the colour was enormous i but since it has been manufactured artificially the price has been greatly reduced, and ultramarine can now be obtained at a fraction of the priooformerly paid for it

Although its oil;, hauyne, is cry stalUaed, lapis tazali ooours in a massive state, being found in crystalline limestone on the banks of the Indus; and in granite, in Persia, Ohina, and Siberia. It is used in mosaic work, and costly vases are made from it ; but it is also worn as a jewel.

Borsoite. — This mineral, though not a gem, is included here account of ita hardness, which is that of quartz. In the table for the determination of minerals it is placed with tourmEkline, which it resembles by containing boron, and also in becoming electric when heated. It contains chlorine, and, mixed with oxide of copper, will colour the flame azure blue. It is rare, bub is found in small white crystals with gypsum and rock salt.

Colours Of Precious Stones.

name.

s

j

Zircon, Cordierite, . Pbeiutkit, .

R

R

R R

:

R

Scale Op Hardness Foe Precious Stones.

Opd.

5 Apatite (not ft precioaa BtoDe) ; Bcntched by ateL 6'S The hardest glass (imitation gems are Btill softer),

6 Orthoolaae; scratched by hardened steel, Turqaoiae; „ „ „

7 Quartz, amethTit, cairngorm, Tonnnaliiie, . 7'fi Zircon, garnet, . . ./cordierite, . S Topaz, spinel ruby, emerald, beryl, phenakite. 8 '5 ChryeoberyL

9 Corandum (sapphire, ruby, oriental emerald, oriental amethyst, oriental topaz). JO Diamond.

n,g,t,7.cbyG00glc

BTBATiriED DEPOSITS.

Agate,

Eauyne, .

to 2-6

Heliotrope,

Kyanite, ,

Beryl,

Labradorite,

Lapis lazali,

Boracite, .

Olivine,

Ooyx, .

Cat's eye, .

Chalcedony,

Orthoclue,

Phenakita,

Chrysolite, .

to 2-8

:

Citrine, .

Cordierite. .

Sardonyx,

Corundnm,.

Crooidolite,

Spinel, .

Topaz, .

Diohroite, .

Emerald, .

Turquoise,

Epidote, ,

Veeavianite,

Gatoet,

Zircon, .

Chap!

Er T.

Stbatifibd Deposits.

Those claaaes of mineral deposits which come under this head have been formed at the same time as the rocks with which the are iuterstratified, and, indeed, ma be looked upon as rocks themselves.

substances as slate, marble, and the various building stones, which are quarried; coal, some deposits of ironstone, rock salt, and gypsum, which are either quarried or mined ; and, lastly, rocks which are impregnated, to a greater or less extent, with metallic minerals, come under this group.

Begarding those sabstancea which have to be quarried, such AS slates and the various building stones, it is not proposed to enter into any description, while the other two groups require separate treatment, because the former (of which coal may be taken as a type) will be worked so that the greatest quantity of material will be removed ; the latter, so that only that portion token which will be of a remunerative character.

Coal. — It will be of advantage in the first instance to study the manner in which coal has been formed, and thus arrive at Bome of the principles which govern its distribution.

That coal is of vegetable origin may readily he proved by examining a thin slice of that eubatance under a microscope, when the tisanes of plants can he more or less perfectly seen ; but in most cases there are two kinds of structure visible, one the so-called structure of mineral charcoal, resembling charred wood, in which the vegetable tissue cannot be reoogniaed; and the other, composed of round cell-like bodies.

It has been shown that, in many cases at all events, the bituminous or volatile matters in coal are due to these round cell-like bodies, and these have been traced to the resinous spores of plants which are allied to the club mosses of the present day; but unlike these, which seldom grow to more than a few inches in height, the plants to which these spores belonged grew to a very great height, and the climate and conditions generally must have been extremely humid.

lb is now generally oousidered that coal seams were formed on the sites where the plants from which they are derived grew, and, therefore, that the bed of underclay which is frequently found below the coal was the soil upon which these plants grew ; but in some few cases coal seams may have been formed by vast accumulations of drift wood. That most seams of coal were formed in silli is borne out, however, by the occurrence of roots in this under clay.

A careful examination of any section in which seams of coal occur demonstrates the fact that the rocks with which they are chiefly associated are alternating beds of shale and sandstone, with occasional beds of fireclay and ironstone. It is not at all unusual to find a thickness of several hundred feet of these rocks, including several seams of coal of varying thickness and quality, some of which could be worked to advantage, while others are not of sufficient value to pay for mining.

It is seldom the case that these shalea and sandstones contain marine fossils ; remains of plants and occasional freshwater shells are the only fossils that occur in them, and there can be no doubt that they were deposited under conditions which allowed of the growth of dense forests, of their submergence below freshwater areas, and of their subsequent elevation when fresh forests grew, which in their turn were altered to coal. Subsequent depressions on a larger scale have in many cases submerged these coal-bearing beds below sea-level, and rocks containing marine fossils are then found overlying the coal-bearing series.

Btratipibd Deposits. 81

It will be perfectly evident that with the mode of formation described the extent of valuable seams of coal is not aeceaaarily ootenuinouB with the shales aad sandstones with which they are interstratified. The extent of the coal seams will depend to & great extant upon the local conditions which prevailed at the time of their formation ; and whereas the conditions of soil and climate may have been identical over very wide-spread areas, in which case the coal will be of uniform quality and thickness for great distances, it may equally well prove that these conditions were very local, and consequently that the seams vary much in short distances, thinning and deteriorating in passing from one property to another.

It is seldom the oskse that seams of coal are found in an absolutely horizontal position, and so, if they have any dip at all, they are generally to be found outcropping somewhere

or other. Those outcrops

may be, as in mountainous countries, represented by a p liff, frequently with a hard sandstone forming a Boarp, with the softer coal underlying it, as in the accompanying sketch, in which case the cool can

easily be tested and meas- l~Z~II

nred with very little work ;

or, as in flat or undulatine t- c

' . . ,u Fig- 5.— Section.

country, where the rocks "

have been much decomposed, the outcrops may be obscured by surface soil, and then more judgment is necessary in order to decide what work should be done.

The following sketch (Fig. 6) will illustrate the conditions alluded to. Where these prevail, some information regarding the strike and dip of the strata and the probability of coal existing can generally be gained by an examination of creek beds or any ontcrops of rock which exist; after which, a careful examination of the soil will frequently reveal small pieces of coal in it or, possibly, only a black sooty-like smu( in the soil, which will afford some indication of the best places in which to sink small trial holes in search for coal.

Snr&oe prospecting is of the greatest value for deposits of this olasi and shoved always be undertaken before any more expensive methods of testing the ground are adopted. Having demonstrated the fact that a seam or seams of coal exist on any

PEtOSPECTIFO FOR HIITXBALa.

property, the next point that will have to be considered in forming aaj idea of the extent of these coal seams is, to what movements have the rooks been sobjeoted ; what, in fact, are the angles of inclination or dip of the different beds 1 Knowing that sears of coal are stratified deposits, or have been formed during

Fig. 6. — Section.

the same geological period as the rocks in which they occur, it wilt be certain that the ooal seams themselves have been subjected to the same movements as the rocks, and having once settled the position of a coal seam in a section, any further observations of dip or strike may just aa readily be taken In the rocks which crop out at the snr&ce as in the coal seam itself.

To illustrate this by a section ; if it is supposed that a coal seam has been found cropping out at the surface in a cliff aa at a (Fig. 7), and dipping in the direction indicated, the thickness of

Fig. 7.— Section.

the beds to the summit of the cliff can be measured, and then the upper bed traced along the surface towards the dip. Taking advantage of every outorop of rock which is to be seen, and noting the dip of each, an exact idea can be formed of the course of the ooal and the depth at which it will be found at different points. If the dip was uniform, as shown in the section, this would be very simple ; but if, on the other hand, the dip and strike changed at different places, the surface would have to bo studied very carefully in order to arrive at these conclusions.

In the following plan (Fig. 8) let (a) be a seam of coal, cropping as shown, and (b) a bed overlying it, also cropping at the places marked, and dipping as shown by the arrows. In this case, the

8Tbatipied Deposits. 83

mun body of coal would lie in the direction indicated by the large K,rTOw, and coal struck along this line could be worked to the rise in three directions.

A surface study of the groond may thus be of the greatest value in determining in what direction boring operations ean beat be carried on, and may frequently save a great expenditure in useless boring, since it is not a very unusual thing for bore-

Fig. 8.— Flui.

boles to be sunk when the same information could be better obtained by a sur&ce study of the ground.

This sunace prospecting, however, will not inform us what the thickness of the coal seams may be in any particular area, nor give us any notion of their quality. Having by surface work arrived at a conclusion as to the distribution of the beds, boreholes, situated judiciously so as to prove the thickness and quality of the seams, must be put down and an accurate knowledge regarding them thus obtained.

It is an old and true saying that " a colliery well bored is half won " ; but even boreholea will not give notice at the outset of all the troubles which may be met with in the workings. There may be small or even large &ults which have disturbed the seams, and may thus give rise to a large amount of dead work ; or there may be bands of stone and partings, formed during the

81 PfiOSPBOTINO TOK MINIBILB.

depositioD of the coal by streams which carried a certain amount of sediment with them ; or " vash onta " may occur where the coal hu been completely carried avay by running water, and ita placo filled in with sand or gravel j or the coal may even be cut out by dykes of igneous rock, which have been forced up from below, as at Newcastle and Illawarra in New South Wales. All matters such as these can only be determined in the workings, and we must always be prepared to find a fair proportion of difBculties to contend with and oTeroome.

Surface prospecting and boring can, however, determine the area of the coal-bearing rocks in a certain district and can demonstrate the existence of workable seams of coal in these deposits ; beyond this the prospector can hardly be expected to go. There are always elements of uncertainty in mining, and although coal mining ia perhaps the most certain of all, it is not free from disappointments. The quality of coal varies considerably, for while some classes are suitable for steam raising and smelting purposes, others have a much leas extended use; but these characters will be referred to later.

In working ooal it must be borne in mind that everything depends upon local conditions, the thickness of the seams ; the presence or absence of hands interstratified with the coal, and the nature of the roof and floor ; and it ia worth while considering a few points now which bear upon the question.

Seams of coal not more than 18 inches thick can be worked to advantage under special circnmstaacea, but these must all be favourable. The roof and floor must be good ; the inclination of the seam small ; there should be facilities for driving coalontting machinery at a cheap rate ; wages should be cheap and the sale price of coal comparatively high ; and, especially, there should he no competition with thicker seams under as favourable conditions in the neighbourhood.

Seams are worked up to 50 feet, and even more, in thickness ; but no Special advantage exists in working a seam over 6 ft. or 7 ft. thick ; as, although more coal can be won in a given area, the expensea of aupporting the roof and the difficulties of ventilation militate against cheap working. In the early hiatory of a district the cost of working coal is generally at a minimum and even when wages are high, as, for instance, in the United States, there are many cases where outcrop coal is worked at about 4b. per ton; while in England, with lower wages, the coat ia often 7s. per ton (or even more) when worked from shafts, with pumping and surface charges to be considered.

The presence of bonds or layers of ahale or stone in a coal seam ia sometimes very prudicial to the working, indeed, at

times will make au otlierwise valuable aeam nEeleaa; but, ia other coses, where the bands are fairly large and separate easily from the coal, the stone from them can be used to build pack walla in the mine, and they are no serious inconvenience.

Iron Ores. — Deposits of ironstone occur under somewhat similar conditions to coal, but they are much more irregular in their extent. They are frequently found associated with the coal measures, but quite as often are interstratified with beds in which no coal is present. Most stratified depoeits of iron are either carbonate of iron, known as day baiid irontUme; carbonate of iron mixed with some carbonaceous matter, known as black band ironatone; or a hydrous oxide of iron, known as brovtn iron ore. There are also deposits of red hnmatite, the anhydrous oxide, but these are of rarer occurrence.

By far the greater quantity of ironstone mined is brown iron ore, of which the extensiTO deposits of Bilbao in Spain may be taken as a type. The ores are mined and picked so as to produce as high a percentage of iron as possible, and are sold on the basis of 50 per cent iron, so much per unit being paid for each per cent above this. The prices naturally vary somewhat, but from id. to 6d. per unit for ores of 60 per cent and over, delivered in "Wales or the North of England, may be taken as about their value. Evidently the margin of profit in working this ore is slight, and the conditions must be very favourable to allow of a deposit being worked to advantage

Hook Salt and Gypaum also occur under somewhat similar conditions, but hardly merit any special remarks here, although, of course, the salt industry is enormous.

Metollio Ores. — The group of impregnated stratified deposits ia well represented on the Oontinent of Europe by the Bunter sandstone, which in parts of Germany is charged with fine grains of galena, the whole rock at times containing about 3 per cent of lead; and by the copper slate of Germany in which the impregnated rock yields 2 to 3 per cent, of copper, and is enriched at places by veins containing more valuable ores.

At Lake Superior extensive conglomerates impregnated with native copper, and amygdaloids formed by lava-streams, the Tesicles of which have been filled with various minerals including native copper, form the important copper - bearing deposits of that region.

It is of importance to note that such deposits as the Bunter sandstone and copper slate have afforded employment to many hundred men for between 200 and 300 years, and so may be looked upon as deposits of very great commercial importance. This also affords another illustration of the fat that efiWfe

86 FBOBPECTiira worn miitebals.

deposits of thia sort will pay well to work if the qnuitity of ore is Bafficieiit.

Gold Depositfl. — By &r the most important, however, of the impregDAted stratified deposits which have yet been found are the so-called banket beda of the TranavaaL These beds consist of quarti oonglomerateB which are interstratified with shales. The remarkable feature oonceming them is that the pebbles of the ooBglomerates appear to be imbedded in a matrix of quarts, which must have been deposited from solution around them j it is in thia enclosing quarta that the gold occurs. There are several of these beda lying one above the other and separated by beds of shale. In tiie neighbourhood of Johannesbui they have been trnoed and worked for miles along their strike.

The most interesting and valuable fact regarding this deposit is the oomparatively uniform yield of the atone; for while, of course, it ia not all equally rich, experience haa shown that very large areas yield ore which is constantly payable to work, and that by opening the ground on a large scale a constant and Steady yield can be maintained. It ia difficult to account for the origin of theae deposits ; and although many theories have been propotinded, it is doubtful whether any of them satisfactorily explain the occurrence, for it is not easy to understand how the eaotosing matrix of quartz can have been formed unless from siliceous springs which also carried gold ; and if this be their source it is hard to imagine that these springs should have the widespread distribution which would be necessary to explain the phenomena. It is true that some chemical decomposition in inland waters might account for the occurrence, but even this it is hardly possible to investigate at present on the basis of observed facts.

Be their origin, however, what it may, it is certain that the deposits are widespread in the Transvaal, and have opened a field for gold mining such as has never been seen elaewhere, and under conditions which have never before been secured. Instead of the uncertainty of reefs, in which rich shoots of gold are succeeded by barren ports, thus preventing one from forming any estimate of value beyond those portions of the reefs or lodes that can actually be seen, the TrauBvaol beds have been so developed aa to show their continuity in such a manner that, although they are not uniformly rich, they have all the elements of permanence possessed by a coal seam.

Their early history, moreover, did not foreshadow the great value they would ultimately acquire; for it was found that by battery amalgamation only a comparatively small proportion of

OTBATIPIBD DEPOBira. 87

the gold was saved, and it ia due to the cyanide proceBs for the extraction of gold that the succeaa of the Band mines ia due, while it ia equally true that the snccesa of the cyanide process ia due to the Band.

In no part of the world has gold mining been carried on npoa the extensive scale which ia adopted here, and perhaps in no case has capital been so lavishly expended in equipping mines with all the latest improvements, as no expense has Deen spared when succesB could he gained by incurring it.

At the present time the Band mines are yielding over 400,000 ounces of gold every month, approaching a value of X3,000,000 sterling; and there appears no reason anticipate any immedi* ate falling off in the yield.

No similar deposits to these have yet been found, but the prospector should devote careful attention to testing any similar beds he may meet with. It must be remembered that eminent mining engineers did not attach great importance to these beds when they were first discovered on the Band, and it is quite possible that similar beds may be found elsewhere ; the Tarkwa conglomerates in West Africa may or may not he of the same origin. There are certain conglomerates associated with the Oarbomferotts rocks of New South Wales in which gold has been found; and in Spain it is stated that auriferoua conglomerates exist; but in neither case have they been developed. There are many other cases in which rocks have become impregnated with valuable minerals in the neighbourhood of veins and dykes, which will be referred to under the heading of Irregular Deposits; but there is one case to which attention should be called at this place, viz., the Belubnla deposits near Carcoar in New Sputh Wales. These beds, which crop out close to the Belubula Biver, rise as a small hill, are regularly stratified, and dip towards the river, aa in the following section i—

Pig. 9.— Section.

In a vertical section of about 90 feet, over 60 feet in thickness ia composed of material carrying gold.

The auriferous beds are of a fine sandy nature, and are very easily crushed, while the beds with which they are interstratified are of a slaty character, and are stated by soma

obseirers to be very tine graioed " laccoliteaj" the whole eeriea being considered as of igneous origin. There is, however, a very well marked strati ficatioD, and the lines of demarcation between the auriferous and nonauriferous beds are well and clearly defined.

Pittman considers that the ore bodies were porous submarine tuffs laid down contemporaneously with the beds of mud (now forming claystone during intermittent periods of intense volcanic activity, which brought about the induration of the claystones, the obliteration of the original structure by hydrothermal solutions, and the filling of spaces with calcite, silica, and auriferous sulphides and arsenides.

The auriferous beds are not uniformly rich in gold, but vary in their gold contents from mere traces to nearly 1 oz. per ton. Some thousands of tons have been crushed in a battery, and are reported to have yielded between 5 and 6 . of gold per ton.

These surface beds are somewhat heavily charged with soluble sulphates, such as alum, sulphate of iron, &c., which makes it impossible to recover a fair proportion of the gold by ordinary processes, unless the ores are previously roasted.

Working Expenses. — The most important matter for the prospector to bear in mind as regards the occurrence of impregnated minerals in stratified deposits is that, if it can be shown that these impregnations extend over a considerable area, the conditions of working will be such as to reduce working expenses to a minimum. Under no oouditiona in lodes can the ore be mined so cheaply; consequently, if large beds exist, it is safe to calculate that, working on a large scale, very low returns will pay. It is true that a large initial expenditure will be necessary to equip the mine on such a scale as will allow a margin of profit upon low grade ores, but when this preliminary expense has been incurred the business becomes one of an industrial nature rather than the ordinary mining risk. There is little prospect of any sensational returns, but steady profits can be looked for if proper care is exercised iu the management.

There Is yet one point to which attention should be called when considering the working of stratified deposits generally, whether coal, iron, salt, lead, copper, or gold — viz., that the whole success depends in every case upon a most careful attention to detail It must be accepted as a principle that the profit per ton of ore mined will be small, and that a little laxness in the management here and there will very soon convert a surplus into a deficit. When it is considered that, on an output of 1,000 tons a day, a halfpenny per ton represents over .£600 a year, it

Hivbral Veins And Lodes. 89

will be seen that the most rigid care has to be exercised on small details in order to make this class of mining Buocessfiil. It is true that this question, perhaps, hardly affects the prospector but still it should be always present in Mb mind, for he must look ahead and be able to decide whether any property which he secures will bear the investiKation it is sure to receive before he can reap any profit from his discovery; and a thorough knowledge of the conditions which should prevail in subsequent working is the only way in which he can avoid mistakes and an undue expenditure of time and labour in the early history of a mine.

CHAFrEE vr.

Mineral Veins And Lodes.

MiNEBAL deposits formed after the rocks in which they occur are of two kinds: — (a) Deposits in pre-existing cavities; (6) deposits replacing certain constituents of the rocks themselves.

Fre-existing cavities have been formed in various ways, and may be divided into (a) lodes of various classes, (b) some contact deposits, and (c) some deposits in calcareous rocks in which caves have been dissolved prior to the deposition, of the mineral within them. The replacement deposits, while varying much in form, have all practically the same origin, being due to the solution of one class of mineral by percolating waters and a coincident deposition of one of another class. The channels by which these infiltrating solutions have come to their work vary with different deposits, and replacements take place at the junction of igneous rocks and sedimentary strata, where what is known as regional metamorphism has taken place ; in the vicinity of lodes, and again in limestones. It will be seen, therefore, that it is difficult to draw hard and fast lines between the different classes of mineral deposits, and that frequently two or more forms of origin may be illustrated in one mine.

The actual agents in the formation of these deposits are practically the same in every case, although their chemical constitution varies, and it is better to consider this question first before describing the deposits themselves.

In the early days of geological research there were two schools of geologists, one of which attributed everything possible to

igneona origin, while the other sought the &id of water to explain moBt of the observed facts. It ia needleaa to remark that theae extreme views led to a great number of absurd theories being propounded both on one side and the other, but the mode of origin of mineral deposits has remained a matter of dilute after many other points of difierence have been settled.

It has been held by one school that mineral deposits are of igneoDB origin, and have, therefore, been filled from the interior of the earth, and, by the other, that they owe their origin to aqueous agencies and have been filled from the surface; bnt neither of these views can be taken as correct in its entirety. So long as these two theories were held by opposing parties, it was supposed that, if a reef was filled witii fused matter from below, it would necessarily widen as it went down j whereas, if the filling took place from the surface, the width of the reef would gradually diminish until it at last pinched out It may bo safely affirmed that in no case have the walls of lodes beea altered by other means than an infiltration of silica, which frequently hardens them, or other chemical change due to the action of percolating solutions, besides which, quartz is far less fusible than most of the rocks through which reefs pass. When the walls of lodes are examined, no signs whatever of fusion can be seen, but many angular prominences yet remain. In many coses, lodes are also found to have a banded structure in lines parallel to the walls, the difierent bands sometimes containing different minerals, showing that the solutions which deposited these minerals varied from time to time.

A consideration of the foregoing phenomena leads to the con< elusion that in every case lodes have been filled directly by crystallisation of minerals from solution, and that the constituents of these minerals have been dissolved &om the rocks through which the subterranean water filtered. In some cases they may have been derived in the immediate vicinity of the lodea in which they are found; and, in others, they have come from some considerable distance, being only deposited when the waters have met with rocks of special composition or other conditions have been favourable.

The following are some fiimiliar instances of the solvent action of water under different conditions : —

Limestone, for instance, is nearly insoluble in quite pure water; but when this water has previously dissolved a certain quantity of carbonic acid, which all rain water takes up in falling through the air, it is then capable of dissolving carbonate of lime. All water in limestone districts is " hard," or, in other

HINBB&I. TEIlirS AKD L0I>£9. 91

words, contains carbonate of lime in solution ; and the caves, which are always found in limestone, show the extent to which solution has gone on. Caves, however, not only afford proof that the limestone has been dissolved, but show also how it may again be deposited, the stalactites which hang from the roofs and the stalagmites on the floors having been thus formed. In many cases deposits of calcareous sinter occar on the surface, and some remarkable deposits are found in mines, to which allusion will be subsequently made. The action of carbonic acid is not, however, limited to the solution of carbonates, bnt haa also the power of decomposing many minerals, such as the felspars, in doing which it dissolves the alkalies in the form of carbonate, and sets free silica in a soluble form. Quartz is also soluble in these solutions of alkaline carbonates.

The solvent action of water charged with carbonic acid is greatly increased when either the temperature or pressure augmented, while, with decrease of temperature or pressure, the substance held in solution is (ain deposited.

As a proof of the foregoing statement, reference need only be made to the botspringa of the Rotomahana district, N.Z., where, before the Tarawera eruption which destroyed all the terraces which had been deposited by these springs, all the actions specified were going on. The water came to the surface charged with carbonic acid, which was given off when it reached the surface, the pressure having been diminished, and the silica which had been dissolved from the rooks through which the water had passed was again deposited as sinter, forming the &mous white and pink terraces. The silica held in suspension by the water was the canse of the bright pellucid blue colour so characteristic of these springs. The sinter consisted entirely of silica, while carbonic acid was evolved in large quantities at the geysers.

Sulphuretted hydrogen is not less important in the chemical laboratories of nature. As a gaa it issues from springs in many districts, being readily recognised by its unpleasant smell like rotten eggs. This gas has properties which are relied upon for many reactions ia analytical research. It precipitates some metals in acid, others in alkaline solutions; but most of the metals are dissolved in alkaline sulphides.

It ia essential to remember that in all cases, whether water be charged with carbonic acid or sulphuretted hydrogen, the solvent action is greatly increased by pressure or heat ; and that when the temperature ia lowered or the pressure decreased deposition will ensue. This is the principal reason why minerals have been

deposited in logos, for it must be borne in mind that tbe water circulating in lodei cannot be ntider the Bame preasare as it was when in the pores of the rocke, and that as it rises towards the nrface the temperature Bteadily decreases.

As an illnstratton, an extract may be quoted from Air. G. F. Becker's report on the geology of the Oomstock lode {U.S. Geologia:U Survey, 1880-81) :—

"Baron von Bichthofen was of opinion that fluorine and chlorine had played a large part in the ore depoaitioa on the Comstock, and this the writer is not disposed to deny ; but on the other hand, it is plain that most of the phenomena are sufficiently accounted for on the supposition that the agents hare been emily solutions of carbonic and hydros utphnrio acids. These reagents will attack the bisilicates and felspars. The result would be carbonates and sulphides of metals, earths and alkalies, and free quartz ; but quarts and the sulphides of the metals are soluble in solutions of carbonates and sulphides of the earths and alkalies, and the essential constituents of the ore miglit, therefore, readily be conveyed to openings ia the vein where they would have been deposited on relief of pressure and diminution of temperature."

" An advance boring on the 3,000 feet level of the Yellow Jacket struck a powerful stream of water at 3,065 feet (in the west country) which was heavily chained with hydrogen sulphide and had a temperature of 170* F., and there is equd evidence of the presence of carbonic acid in the water of tbe lower levels. A spring on the 3,700 feet level of the Yellow Jacket, which showed a temperature of above 150° F., was found to be depositing a sinter largely composed of car bonates."

But it is not necessary to turn to America alone for illustrations of the filling of reefs, for any mining district which has been sufficiently studied will afford subject for reOection. In the Thames Goldfield, New Zealand, for instance, most of the phenomena alluded to are very clearly demonstrated. The country rock consbts of numbers of stratified bands of submarine volcanic rocks, some of which are bard, green, and undecomposed ; others consist of a softer white rock in which the felspars have suffered decomposition, and the rock itself ia charged with numbers of small crystals of pyrites, especially near the reefs. Tbe rock is also traversed by numerous smaU black veins, chiefly sulphide of iron and antimony, and it is in these decomposed rocks that the richest deposits of gold are found in tbe reefs. All miners who are acquainted with the

hull, .. A''."->'ll-'

HINBBAL VBIK8 kVD LODES. 93

ThKmes Ooldfield will recognise the carbonic acid which has been alluded to in the heavy gas so prevalent below the 400 feet level, and which render! ventilation so difficult. The Big Pump affisrds an illustration of the quantity of carbonates held in solution under pressure and ready to be deposited when this pressure is removed; and the records of the Pumping Association show that a vary heavy expense was incurred in cleaning the columns from the incrustation of carbonates, which, during the earlier days of the deep levels, formed with almost unprMedented rapidity.

Although free sulphuretted hydrogen has not been detected in this locality, it evidently existed during the charging of the reefs.

It is a well-known fact in all mining districts that the junctions of lodes are generally the richest points, always supposing that the junction takes place in " kindly country"; the explanation of this is simple on tbe aqueons theory of filling of lodes.

Water traversing two different channels of necessity passes through different belts of country, and thus holds different substances in solution. As a case in point, suppose the water in one channel contains carbonates of lime and alkalies in solution, as well as silica derived from decomposition of felspars ; and that the other, charged with sulphuretted hydrogen, brought with it sulphide of antimony dissolved in sulphide of lime. The result of these two waters meeting would be that carbonate of lime would be formed, sulphuretted hydrogen set free, and sulphide of antimony deposited, as well as tbe silica which was formerly held in solution by the carbonic acid.

Numbers of such illustrationB might be given, but it is not the object of this book to explain all phenomena which occur in lodes, bnt merely to direct the observations of prospectors into tlie right channels.

It is well known that in every district certain rocks are more "kindly" for one special mineral than for any other. Limestone, for instance, is very often the rock in which galena occurs; while gold is frequently closely related to diorite. In snob cases the solution carrying the metals may have traversed various rocks flowing sometimes for great distances without meeting with conditions favourable for deposition, and only have met with these conditions when it reaohed that belt of country which we, in working the mine, designate "kindly ground," where, by an interchange of materials, by chemical action, in fact, deposit tion ensued, and shoots, bunches, or courses of ore were formed as the case might be.

9i PBOSFECriita fob hirebals.

This raiEBs the very interesting question of the origin of gold and other minerals which have occnmulated in lodes, and a very close relationship can hardly fail to be traced between the rocks encasing the lodes and the mineral deposits which occur in them. In connection with this a quotation may be permitted from Mr. F. S. Emmons's report on the minliig industry of the Leadville district, Colorado, because it very well expresses the views it is desired to enunciate. He says : — " The earlier geologists devoted much speculation to the subject of the origin of metallic minerals in ore deposits, and arrayed themselves on the side respectively of the Neptauists or Flntoniats, according as they believed them to have been brought to their present position by descending or ascending currents, whether gaseous or liquid. As pure theory has been gradually modified by the results of actual investigation, the upholders of the two opposing schools have come to concede in this, as in other questions of general bearing on geology, an element of truth even in the views of their opponents. Only extremists maintain that any series of geologiccii phenomena admit of but one explanation, or are due to one universal immediate cause. It is generally agreed that subterranean waters, however deep seated their apparent source, came originally fhim the surface. It is, moreover, proved that no rocks are absolutely impermeable to -water, but as on the earth's surface, so within its solid crust, there is a constant circulation either through capillary pores, where it is not readily visible, or through the larger and more apparent channels formed by joints, cleavage planes, faults, dykes, and stratification lines, the direction taken by such waters varying with different local conditions. In the case, therefore, of ore deposits, which are derived from aqueous solutions circulating within the earth's crust, a class which is constantly augmented by scientific investigations, the question as to the immediate sources of the metals in solutions from which they were deposild, whether above or below the present position, is one which must be determined independently in each individual ease, and to which no general answer can probably ever be given."

A few examples may be mentioned in illustration of the foregoing remarks. At Adelong, N. B. Wales, the reefs traverse a hard, nndecomposed syenitic granite, and are undoubtedly true fissure reefs ; but the country rock from the surface to the lowest levels exhibits no appreciable change in its composition, the granite throughout being a hard, solid compact rock. The lodes themselves, however, are nut completely filled with quarts,

Mineral Veihs And Lodes. 96

but &re really after channels of country largely composed of chlorite ; and all those parts which were not filled mechanically have since been charged with auriferous quartz by the cironUting vaters. In t~bis case, the deposition of the gold and quartz was probably due to chemical changes induced in these softer channels, and not in any way to the decomposition of the solid granite itself. Grenfell, on the other hand, which is also in N. 8. Wales, may be taken as a case in point where the rock has exerted a powerful infioenoe on the mineral deposits. The rock in which the richest deposits of gold occurred in the Consols Beef was a dark-coloured porphyrite containing a darkgreenish mica, while in the lower levels, where the reef ceased to be payable, no mica was to be seen.

In this case, the presence of mica in the rock appears to point to the class of ground which possessed the necessary substances for precipitating gold, and shows how necessary it is to trace the extent and boundaries of different classes of rock.

Even more marked than this is the case of the Thames, where the shoots of gold can be traced through several different belts of rock with which other beds are tnterstratified, in which gold does not occur in payable quantities; and a section of the Albumia Mine will illustrate this varying character very well, those belts marked a fFig. 14) being the hard and unproductive

Fig. 14. — Section through Alburnia Mine.

country. It is often the case that the charging of reefs is attributed to what is known as solfotaric action, the final stage of volcanic eruption when only steam and gases are emitted from the craters being called the solfatara stage. In Mr. Becker's report on the Corostock lode, which has already been quoted, he shows, in a section from Mount Davidson through the upper end of the Sutro tunnel, several belts of country which have been decomposed by solfataric action, although it is worthy of notice that none of these bands approach the Oomstock lode itself, which occurs at the junction of diorite and diabase at its outcrop, but intersects the diorite in depth.

In hia earlier report oq the Mount Morgan gold deposits, Mr. K, li. Jack, Goremment Geologist for Queensland, attributes bfae occurrence of gold at that place to deposition from a hot spring. The countiT in the immediate vicinity appears to be traversed by dykes of rbyolite, and there are coDsiderabte deposits of siliceous sister resembling in character the deposits of geysers. It is in association with these siliceous sinter deposits, as well as with brown and red hematite ores, which might justly be described as gossan, that the gold occurs. It is perfectly reasonable to believe that deposits of gold may be formed in this manner ; indeed geysers and hot springs generally afford the best illustrations of many of the operations going on during the charging of reefs, and in isolated cases, such as Mount Moian, substances of economic value may well be introduced ; but it must be borne in mind that nearly all lodes which contain iron in any form, notably as iron pyrites, decompose near the sur&oe to form a porous kind of hwmatite which is known to miners as "gossan," and that this gossan will sometimes extend for a depth of 100 feet to 160 feet from the surface before the true ore of the mine is met with.

It is very questionable whether the theory of deposition from a hot spring is correct in the case of Mount Morgan, or whether the deposit is simply a lode which has opened to very large dimensions ; later developments appear to point to the deposit being nothing else than a lode.

Gossans are due to the oxidation of ores containing iron, and all substances in a lode which oan be readily oxidised are so changed when exposed to the action of the weather above ground water-level. When copper pyrite, for instance, is present in the ore, the copper is changed to sulphate, which is carried away in solution, while the iron remains as a porous gossan.

Noble metals, such as silver and gold, are rarely carried away in solution, but silver is frequently changed to a chloride. Alt silver mines afford illustrations of how tMs action has gone on.

Bearing these points in mind, it will be evident that the character of a gossan will seldom afford any index of the true nature of the lode it covers. Generally speaking, lodes which have a good gossan on the surface are valuable in depth for one class of mineral or other ; and a gossan which has a snofly-brown colonr and great porosity may generally be looked apon as the beat indication.

Traotoilng of Books. — Bearing in mind the nnmerouB movements of elevation or depression to which strata have been subjected since they were originally formed, and the dislocation

Its And Lodes. 97

to which theae movementa have givea rise, it becoinea possible to investigate the origin and characters of metaliiferooB deposit occurring in lodeB or fissures in the rocke.

It will at once be apparent that when sedimentary strata in an unconsolidated condition are raised from the sea, tilted from one end, or even folded into a number of anticlinal and synclinal curveB, they will still be in a sufficiently plastic condition to adapt themselves to any Iresh form which they have to assume. This is the reason why the you&ger sedimentary rocks seldom contain mineral reins unless they have bean bend rapidly by some local cause. On the other hand, where strata have, during the lapse of ages, become consolidated, and changed from mud, sand, or clay, to shale, sandstone, or slate, either in consequence of great pressure or chemical action ; or where they hare been further subjected to the process of metamorphism and thus assumed the characters of quartzites, schist, or gneiss, it will be evident that any further movements of the rocks must be attended by the formation of cracks or fissures trarersing them, because they are no longer sufficiently plastic to accommodate themselves to new forms without breaking.

Any granitic upheaval, or intrusion of other crystalline rock, tilts the adjacent beds, and, if these are hard, forms a number of cracks or fissures in them, following a direction parallel to the line of upheaval. These cracks are of two kinds, viz., those which dip or underlay away from the line of elevation, and those which are inclined towards it.

Bocks are of very different degrees of hardness, and, when broken, the line of fracture will vary in angle in the different beds. Prospectors hardly need to be told that this is the case, for they know from their own experience that difiTerent closes of rock break very differently when struck with a spalling hammer; some have a clean straight fracture, others break with curved faces, and others split more readily in one direction than in any other.

The varying angle of fracture in different classes of rocks haa been the primary cause of the opening of mineral veins or fissure lodes, as will be demonstrated shortly; but in the meantime the fact is of the greatest importance to be remembered.

It ia seldom the case that the line of elevation is ezactl; parallel to the line of strike of the beds, since these have generally, while in a plastic condition, been subjected to certain plications. Hence, in by far the greater number of cases, lodes pass through several difierent belts of atrata; thus a lode, instead of being represented by a straight line on the surface, follows a

iinuOBE coune, which ia determined by the characters of tha rocka through which it paaaea.

In investigating the history of the formatioD of lodes it may be auDmed that a granitic bosB has been forced upwards and haa tilted and fractured the rocks resting upon it ; and after this some settlement of the rocks haa again t&ken place before they assumed a stable condition. These movements are attended with results which may be illustrated by the following diagram : —

Fig. 10. —Section.

The upheaval forms cracks through the overlying strata from (a) to (6), these cracks dipping away from the line of elevation represented by the granitic Ixms ; a settling down of the beds results in a sliding of the rocks on the hanging wall side of the fissure over those on the footwall side of it.

It has already been pointed out that the cracks do not traverse the various beds

Fig, n.— Section,

at a uniform angle, and ai . when a sliding takes place of one uneven surface on another, the result will be that certain parts of the lode remain closed, whilst other parts are opened. This is shown in Fig. 11. Underground channels are thus opened which are subsequently filled with the various minerals form* ing lodes.

The opening of fissures in this manner can easily be demonstrated by drawing an uneven tine on a piece of paper, tracing this line and allowing the tracing to move on the original. The result will be seen to be that the steeper parts of the lode are opened, while the flatter portions remain closed.

The settling down of the granite boas gives rise to another series of cracks, which underlay towards the line of elevation (as

Hinebal Veins Amd Lodes. 99

sbovn in the sketch), and these open in the same manner by the sliding of the hanging wall on the footwall in the granite area, the sedimentary rocks having by this time come to rest.

Iiodes. — These movements are attended by the formation of a number of intersecting lodes in the region of a (Fig. 11), where the two series of fissures meet; and many secondary lodea might also be formed having a less angle of inclination than the principal fractures; also, since these cracks must terminate at soma point or other, cross courses are produced having a direction nearly at right angles to the average strike of the true ree&. These croaa oonraea may be either barren or productive, as the conditions of the country are favorable or not. The ultimate result of these movements is to form a number of underground galleries through which water can circulate freely, and these subterranean waters deposit the various minerals found in lodes.

The sections (Fig. 12) show that, in a simple fissure, the steeper parts of the lode will remain open, the fiatter portions

f m

Fig. 12.— Sections.

being closed ; and that in the secondary fissures joining the main lodes the reverse will he the case, because the wedge-shaped block between the two fissures would be bat slightly displaced, while the block of country which formed the hanging wall of the main lode and the footwall of the secondary lode would slide on the footwall of the main fissure, and bence open the fiatter portions of the secondary fracture.

There are many districts in which the cause of upheaval is not apparent, no boss of granite reaching the surface, and yet the characters of the reeb point to an origin such as described ; but there are many other localities, of which the Galgong Goldfield, New South Wales, may be cited, where there have been other agents at work in the formation of reefs. At Gulgong the auriferous lodes are very closely related to dykes of diorito which penetrate the Silurian slates of the district, and the same may be said regarding many of the lodes of Western AustraliA.

100 PBOSPECTlirO FOR MINERALS.

These dykes have clearly liad something to do -wiib the origin of the lodes, and have, moreover, determined to a large extent their anriferoue character. They intersect the strata at various points and vary greatly in thickness; but where the strata are not penetrated by them the reefs do not appear to be auriferous, while the greater quantity of gold is in leaders traversing the diorites themselves.

In districts which are traversed by dykes, another series of considerations cornea in. These dykes have been formed by the fracture of the strata from some cause or other, and the wedging asunder of the beds by fused rock under great pressure. As this rock cooled, a number of cracks would be formed from shrinkage, which would not necessarily follow any special direotion. At Gulgong the beds are traversed by a great number of flat-lying leaders, which, in many cases, die out entirely when they reach the junction of the intrusive rock with the sedimentary beds. It is more than probable that reefs which have no connection with these flat leaders, and were farmed contemporaneously with the intrusion of the dykes, will yet be found traversing the adjoining slates.

Lodes traverse strata which have been tilted at all angles, but are never continuous throughout their coarse in one particular bed. This leads us to the consideration of the distribution and extent of the rich parts of lodes.

As lodes vary a great deal m size, from a few inches only to hundreds of feet in width, it is evident that the cavities which have since been filled in the larger lodes could not have been opened in one operation, and that they represent a series of consecutive movemenbj and fillings. There are also many cases where the hanging wall of a lode is well defined, and the footwall obscure, the mineral sometimes penetrating the country as veins, and at others replacing the rock itself. In cases like this, the iracturiiig appears to have shattered the adjoining rock so as to allow of the entry of the depositing solutions without being accompanied by any great movement.

Distribution of Ore in Lodes. — It is apparent that when the angle of underlay of a lode conforms more or less closely to the dip of the strata which it intersects, the character of the lode in depth will be more uniform than when it intersects a number of different belts of rock ; because the angle of the One of fracture will be uniform over greater areas. Even, however, in cases of this sort, sufficient differences in the physical ooa< ditions of the rock will exist to make the fracture more or less irregular, and so there will be portions of the lode which ore wider than others.

hull, .. A''."->'li-'

MINBRAL TEItrS AND LODBB.

When, on the other hand, the strike of a lode corresponds oyer long distanoeB with the strike of the str&ta, but the lode anderlajB at a steeper angle, and thus intersects a nnmher of different bands in depth, constant changes in yalne wiW be found in sinking, but more or less uniformity horizontally ; this constitutes the difference between lodes in which the ore occurs in shoots, and those in which it is chiefly found in flats or courses. When a lode which is underlaying at a steep angle also crosses the strike of flat-lying strata, it will intersect a number of different rocks, both along its course, and also in depth; and the ore will be distributed either in bunches, which have a very limited extension in every direction, or in very flat dipping shoots. As the course of the lode varies so as to more closely assimilate to the strike of the rooks, the horizontal extension of these bunches increases ; while, as the strike of the lode approaches a direction at right angles to the bedding of the strata, the deposits occur in shoots, which dip steeper and steeper in the reB as their direction more nearly approaches a right-angle to the bedding of the strata.

The following sketch plans are designed to illustrate the manner In which shoots of ore dip in lodes under different conditions, but the best idea can be gained by making a model and cutting sections through it in various directions.

Plan. Plan,

o, Dip of country ; b. Underlay ot lode ; c. Dip ot al

In the foregoing il lustrations, when the dip of tho country increases, tbe shoots of ore more nearly approach the vertical ; and when strata standing on end are intersected by a vertical reef at right angles to the coarse of the beds the shoots of ora are Tertical, and practically occur as pipes or columns of ore.

It will be seen, then, that the character of the rock or country exerts a very great influence on the behaviour of lodes and on the distribution of the rich parts ; this has been proved, beyond doubt, to be the case in every district which has been carefully studied. Every prospector is acquainted with the term "kindly ground," which Is used to designate those belts of rock which are favourable for the occurrence of mineral deposits ; but the characters of these belts vary greatly in different districts, and their local characters must be determined in each district which' we may be called upon to examine.

As a general rule, those rocks which are moderately hard appear to be the most favourable for the occurrence of ore, because they possess sufficient coherence to remain open when they have been fractured, and do not offer too great a resistance to fracture in the first instance. The softer rocks, such aa shales, seldom carry valuable deposits ; because the fissures formed are not likely to remain open as channels, but are quickly filled with fallen matter from the hanging waU,

The foregoing remarks give some idea of the manner in which the various lodes have been originally formed by fraotnres in the rocks, how these cracks have been opened by the action of gravity so as to form underground galleries through which water could circulate freely ; and a study of the lodes themselves furnisbes fresh confirmation of the facts that have been stated. It is found in many cases that the walls of lodes have been smoothed, polished, and striated by the sliding of one rough irregular surface on the other, and the direction of the striations shows the direction in which this sliding action took place. Where rocks are not sulScieutly hard to preserve the striations or " slickensides," a thin clayey parting or " flucao," separating the lode from its walls, is frequently found, which, it can hardly be doubted, has been formed oy the grinding of the rocks. The walls of lodes, for some little distance on either side, are also, in many instances, somewhat shattered by the movement which has taken place ; and, at times, as for instance in the Alburnia mine in New Zealand, this change has been bo marked as to give rise to the supposition that the rock alongside the lode was different to that a short distance away; and that the bedding of the country corresponded with the underlay of the lodes

Hinebal Veins And Lodes. 103

themselves instead of intersecting them at a flat angle, aa ia really the case.

A study of reefs will also convince na that they have been deposited by the ency of water, for in many caaes the mineral is arranged in a series of bands or zones parallel to either vail. In manycasea also the iralls have been altered by chemical means, eometimes for great distances from the lodes themselves ; thus, in tin districts, the granite is often decomposed or kaolinised by the action of percolating water; while, in other localities, the valla are sometimes hardened by silicification of the rocks.

Ko lode has ever been formed by the intrusion of quartz in a fused condition. A very few moments' consideration will convince the practical prospector that this is the case, for quartz is one of the most infusible substances known ; so infosibte, in fact, that in many of the volcanic rocka, in which free quartz occurs, no doubt can exist that the crystals were formed in the internal laboratories of the earth and floated to the surface in the molten magma, a fact which is borne out by a microscopic examination of the rocks, when the linea of flow can be traced around the crystala Quartz, then, being of so infusible a nature, would, if it had been inti-uded in a molten condition, have been sufiiciently hot to melt the more readily fusible rocks through which it passed, and any theory founded upon the supposition of filling from below by the agency of heat is neceasarUy wrong, as the walla of lodes never show any evidenoe of having been subjected to a heat sufGciently intense to fose them.

Studying lodes, then, as simple fissures, the conclusion is arrived at that the average underlay of a lode does not in any way determine its ore-bearing properties ; but that, even in the same district, lodes may be vertical or lie in an almost horizontal position and yet be equally productive ; bat the auocessive inclinations of the different parts of lodes are of the greatest importance in determining the diatribntion of the rich parts. As a general rule, the steeper parts of lodes are the richest, although this is not an invariable rule ; the reverse being often the case when hanging wall leaders make junction with a main lode.

There are many other points, however, to be considered conceming the diatribution of the rich parts of lodes. It will be remembered that lodea follow a sinuous course along the surface or along any level in a mine, and so the rich parts will be unequally distributed along a horizontal line. This irregular distribution also depends upon the different rocka through which the lode passes along its course, and sinoe it is generally found that the richer parts are those in which the lode corresponds in direction most neiurly to the line of elevation, this

104 PRosPECiiiia roR hinbrals.

distribution of the rich parts in the upper levels of & mine will frequently serve as a guide bj whicli to determine ttie "kindly country" of any particular district ; and a geological examination of the district will afford data by which it may be inferred in what direction the shoots of ore dip in the lode itseli

Observations have hitherto been conGned to a single fiaaore produced by a single upheaval or movement, but single fissures or lodes are of most unusual occurrence, and it is notorious that where thsy do occur they very seldom contain a auf&cient quantity of valuable mineral to pay for extraction. As a rule, the force which has produced one vein has also produced a series of others parallel to it ; and it is a noteworthy fact that where the behaviour of one of these has been determined, the behaviour of the others and the distribution of the rich parts can generally be predicted with some precision from a consideration of the conditions enumerated.

In the more known and better opened mining districts, such as Oornwall and Freiberg, it has been shown that several successive series of lodes have been formed by tiltings of the strata from different points; and that the lodes following particular conrses are generally characterised by special minerals ; but the less known mineral districts have not yet been sufficiently studied to state these facts authoritatively.

These upheavals of the strata along different lines have not only opened a series of fresh reefs each time — the younger ones intersecting those which have been previonely formed — but in not a few cases, the later movements have re-opened some of the old reefs in an irregular manner, and so some of the accessory deposits have been formed, which are frequently so difficult to account for, bat which are met with in lodes from time to time, apparently defying all attempts to explain their origin or to predict their extent.

Bicb deposits in lodes are alBO cut off abruptly at places by slides or faults, but these and the means to be adopted for the recovery of lodes will he studied in Chapter VIII.

It will be seen from the explanation which has already been given concerning the origin of the fissures which have since been filled with different minerals, that all true fissure reefs must necessarily thin out and widen a great number of times between their outcrops and that point in depth at which the difficulties of working exceed the value of the mineral, for no true fissure vein has yet been proved to die out entirely in depth.

It is stated by many authors that another series of veins, known as "gash veins,' does exist; but their occurrence is of a

Irbeovlab Deposits. 105

very doubtful nature. They are variously described aa "lenticular cavities," " veins confined to one formation," Jcc., -without regard to their mode of origin, and bo include several classes of deposit which should be otherwise classified. Oasb veins, if they do exist, may be regarded as lodes formed by the folding of strata after consolidation ; those occupying the anticlines being necessarily wide towards the surface and narrower as they descend ; whilst those occurring in synclines would widen in depth until the next underlying formation was reached, when they would cut out. It is possible that the saddle reefs of Victoria (which will be described in the chapter on Gold) might belong to this class of deposits, hut by far the greater number of the so-called " gash veins " belong to one or other of the irregular deposits to be presently described. When a true lode appears to pinch out, it will inevitably widen again lower down ; and when it is out off by a slide, it may be found again heaved for a greater or less distance either to the right or left. What the prospector or miner has to decide is whether it is worth his while to spend the time and money necessary to again recover a lode that hu been lost.

Chapter Vii.

Ibbeoular Deposits.

A GREAT number of the repositories in which minerals occur come under one or other of the divisions which are classed aa irregular deposits, and, in some cases, they are of very great importance. Their irrognlarity, however, makes the extent of the ore even more uncertain than in lodes, such as have been described in the preceding chapter, and no rules can be enunciated which afford any guide as to their distribution. In certain cases huge deposits of ore are found which yield vast quantities of mineral; in others, a little ore occurs in bunches, always inducing further prospecting, but not always leading to deposits of sufficient extent and value to repay the cost of exploratory workings. These irregular deposits are, in fact, of the moat speculative nature, and, while they at times result in the aocumnlation of large fortunes, they as often, or perhaps mors frequently, only lead one to expend money on prospecting which is never repaid. It is unfortunately the case ttiat no one, however experienced, can say with any certainty whether it ia judicious to continue prospecting work on a particular deposit or

to abandon it, for, when the ore is poor and of amall extent, a few feet driTsn may completely change the aspect of afiaira and render a mine which had no enoonraging features one which has a very considerable prospective value.

These irregular deposits may be subdivided as follows : —

5. Contaot depoaita. S. Cave deposit!.

A description of the conditions of each of these will be given in this chapter, with some illustrationa of their occurrence.

ImpregnBtionB. — It will be remembered that in the chapter on stratified deposits some instances h&ve been given ot the impregnation of beds by copper, lead, and gold, in which somewhat constant characters prevail over wide areas ; but there are also rooks, frequently of igneous origin, which are impregnated with mineral in a most irregular manner, and which, at times, have been worked to considerable advantage. The cause of these impregnations ia not always, or indeed often, easy to find, but frequently a joint in the rocks, looking like a wall of a lode (sometimes with a thin vein of quartz, calcite, or barytes) forms an indicator vein, and the impregnated rock lies on one or other side of this indicator, and occasionally the rock is impregnated with mineral on both sides of it The distance to which this impregnation extends from the indicator ia very various, and when cross cnt may prove to be only a foot or two wide in places and at others to extend for a hundred feet or more.

Frobably the best illustration that can be found of this class of deposit is in the mines of the Calico District, near Lob Angeles, in Southern California, the rock of which district ia andesite. The nature of the rock varies a good deal in different parts of the range of hiUs which rises from the edge of the Mohave Desert; but they are almost devoid of vegetation, and have weathered in large patches of iron red, pink, and green, thuB affording a most curious patchwork appearance when seen from a distance, and one which would inevitably attract attention.

These rocks are traversed by veins, such as are described, and are impregnated with chloride of silver in a very irregular manner, but over a very wide extent. The ore is of a free milling oharacter, and is worked by battery and pan amalgamation, the Boss continuous system being adopted. The deposits have been sufficiently rich at times to give rise to much litigation

Irregtilab Deposits. 107

between the respective companies which have been working them ; but, taken on an average of the good and bad worked, they have yielded about 10 oz. of silver per ton of ore.

In some cases huge chambers, which can only be likened to caves of the largest type, have been excavated, the whole of the rock broken having been crushed and the silver extracted ; while in other parts of the mines, drives many hundreds of feet in length, have failed to develop any ore that is of sufficient value to pay for extraction. It will be evident that mines of this class require the most constant care in sampling and assaying, and a rough system of testing whether the rock carries silver is practised in the mines, while regular assays are mode day by day of all ore that shows sufficient indications to these rough tests.

Very closely related to these are the so-called fahlbands of Kongsberg, Snaram, and Skutterud in Norway, which are regarded as impregnations by von Cotta.

They are described by J. A. Phillips as " parallel belts of rock of considerable width and extent impregnated with sulphides of iron, copper, and zinc, and somBtimes also with those of lead, cobalt, and silver." The fahlbands of Kongsberg are worked for silver, and are about 1,000 feet thick ; but it is only in a few localities where they are sufficiently rich to pay for working. They are traversed by veins which are unremunerative in the gneiss and schists, but become highly argentiferous in passing ttirough the fahlbands or grey beds, which exert the same ioduence on the veins traversing them as the ordinary "kindly country " does upon reefs or lodes in general, so that, in reality, these fahlbands hardly deserve to be considered as an independent class of deposits.

The cobalt deposits of Snamm and Skutterud also occur in &hlbands which are sometimes rich enough to pay for working, but these, unlike those of Kongsber are not traversed by mineral veins, and so would be more properly considered as imprepiationa.

In Western Australia there are decomposed rocks of considerable width which carry a little gold, but none have been found up to the preaent which will repay the cost of working. The occurrence of gold in this country in lodes in which the gangue is not pure quartz, but a ferruginous material containing, however, a large proportion of silica, appears to have led prospectors to think that every decomposed rock met with was of the same nature; and they have accordingly named these decomposed rooks "lode formation."

A coQBiderable amoont of work has been expended on these ao-called "lode formatiooB" without, however, demonstrating the fact that any of them are payable; while the lodes themselTeB, which these deposits are aupposed to resemble, are the richest gold producers yet found in the colony.

Betioulated Teina (Stockworks). — In some districts certain belts of rock are traversed by a great number of small veins which intersect the country in all directions, forming a perfect network. Where these veins contain any mineral whidi is of economic value, the whole of the rock is crushed for the mineral which it contains. Where reticulated veins occur, the country rock itself is generally impregnated with the mineral aa well; and, in some cases, the impregnation has no doubt been brought about by the infiltration of the mineral waters which charged the veins ; while, in other oases, the rock was impregnated first, and the veins derived their mineral from the rook.

Deposits of this sort are called Stookworka. Tinstone ia fi:queutly found under these conditions both in Cornwall and Germany. Gold occurs under similar conditions at the Thames, ITew Zealand, as was seen when a portion of the spur on the Caledonian mine was crushed ; and in many other mines a good deal of country rook is crushed when small veins traverse it.

Deposits of this class are of sufficient importance to merit some attention, and it should be borne in mind that when a number of small veins of mineral occur comparatively near together, which would not pay to work individually, it may be quite worth while to treat the deposit as a whole.

Lenticular Aggregations. — Certain minerals, notably ironstones and manganese, are found occurring in masses which very frequently coincide with the bedding of the rock, but which thin out in all directions. They have probably been deposited during the formation of the rocks themselves, and are exceedingly capricious as regards their extent and mode of oocurrenoe ; for when one deposit has been worked out no guarantee whatever exists that any more ore will be found in the district. These lenticular aggregations vary in size from small patches only a few inches across, up to masses of many thousands of tons.

Where minerals occur under these conditions, they have probably been precipitated from solution, in inland waters, by decomposing organic matter, such as wood or the leaves of trees, both of which are frequently found fossilised in beds of ironstone. The deposits of iron ore being formed in some of the Norwegian lakes are worked by tbe peasants of the district daring tha winter months by breaking the ice and dredging out the ore.

Irrequlab Dbposits. 109

Irregular HaSBes include a greaC amber of depoaits, some of which are intimately associated with true fissure lodes, of which they appear to be offshoots; whilst others do not seem to be in any way connected with veins, although they have probably been formed in the same way as fissure lodes; others agaia are nothing more than shrinkage cracks produced during the cooling down of the eruptive rocks in whidi they occur. It may frequently be noticed in working a lode that a small vein of ore or gangue goes off either from the hanging or footwall, and when this vein, which is sometimes leas than a quarter of an inch thick, is followed, it opens out to a large mass of ore which is only connected with the lode by the small leader (Fig. 15).

Such deposits as these have been of frequent occurrence in Cornwall, both in copper and tin mines. They are known aa oarbonaB, are at times of oonaiderable size, and contain very rich deposits of ore, They would V appear to be offshoots from .

the lodes, which have been filled by the waters which charged the lodes themselves; but chemical action Fig, 15. — Sactioo.

has been set up in these cavities, and the precipitation of the mineral brought about.

Mining has been carried on in enormous metasomatic masses formed by the rock being dissolved away and replaced by ore deposits laid down by water currents traversing (a) fault channels, (&) intrusive dyke channels, or (c) channels opened up by the shattering of the rook.

Very closely related to carbonas in point of origin are the socalled tin floors which were formerly of very frequent occurrence in Cornwall, but which of late years appear to have been worked oat. These floors are intimately connected with the lodes, but are generally richer than the lodes themselves ; indeed, in many cases where the lodes are absolutely barren, the floors have been very rich. They consist of flats of ore corresponding with certain beds of the strata, and die out at varying distances from the line of reef.

Fig, 16 will illustrate this class of deposit.

In a few isolated instances, notably at the Park of Mines, near St. Oolumb, Cornwall, these floors have proved the principal ore-bearing deposits of the mine; but, instead of lying fiat in.

hull, .. A''."->'li-'

this particular instance, they are tilUd at high ansles, running like east and west lodes ; for which they might be mistaken, except for the fact that they pinch out entirely at a short distance from the main north and south leaders, which are themselves onW an inch or two thick.

It will be evident that deposits of this sort must have been filled by the waters which traversed the reels ; these floors, however, have not been formed as cracks in the rock, but are planes along which segregation has taken place from the country under the influence of the mineralised water in the ree£

A study of the rocks in which these floors occur will afford evidence of their origin and the case of the Park of Mines, quoted above, is most conclusive. Fig. 16.— Section.— a. Lode ; b. Floors. The rock at this mine is elayslate or "killas," and wherever the tin floors are found the rock has been decomposed for some distance from the tinstone, and, the iron in the "killas" becoming peroxidised, the rock is coloured bright red. This is so marked a feature that when, in driving along the north and south leader, the country beipns to assume a reddish tinge, it is a certain indication that tinstone will shortly be met with ; and in working the tin floors any change in the colour of the rock is a sure sign that the end of the ore deposit is beii reached.

Flats of ore are of quite a different character. They bx found corresponding with the planes of bedding in sedimentary rooks, and closely resemble stratified rocks, for which they might readily be mistaken. When these flats, however, are driven on they are found not to thin out in the way lenticular deposits do, but to terminate in a vein which traverses the next belt of country, and will, if followed, generally lead to another flat in a different bed.

The character of these deposits will be best illustrated by a sketch (Fig. 17). They would appear to owe their origin to similar causes to those which have formed true fissure reefs, the lines of least resistance, however, having followed the bedding planes at places. It is not improbable that the cavities thus

IBBEGULAB DEPOSITS. Ill

produced have been enlarged by chemical action, especially where these flats occur in limestone country.

The last class of deposits which comes under this group is known as sesresated veina. These are confined chiefly to igneous and metamorphic rocks, which, in cooling or drying, have shrunk and formed cavities in their interior ; these are at times lenticular in shape, at others nearly spherical, and yet again of very insular form. They must be clearly separated &om true fissure veins or lodes; firstly, because they are limited in extent, and, secondly, because it is by no means necessary for any move- „

ment to have taken place "-8e<*°n.

in order to open these cavities. There is also considerable difference between the way in which true lodes and these veins of segregation have been filled, which may best be illustrated by a description of some of the segregated veins of pegmatite which occur in granite.

These veins of pegmatite have the same composition as granite itself, but consist of much larger crystals, large sheets of mica frequently occurring as well as oryat of felspar of considerable size. These veins are not divided from the enclosing rock by distinct walls, but the crystals of the pwmatite vein frequently penetrate into the enclosing granite. The large crystals have been slowly formed by a recry stall isation of the constituents of the granite after the crack was formed, and a vein of pegmatite afibrds a good illustration of the way in which metallic minerals are segregated in these veins. It will be seen at once that in segregated veins only such minerals can be looked for as are present in the enclosing rock in greater or less quantity; whereas the minerals in fissure lodes may have been carried in solution for some distance. Tery valuable information oncoming the nature of the rock may frequenUy he derived from a study of these veins of segregation.

Contaot DepoaitB consist of accumalations of mineral along lines of junction of two dissimilar rocks which are sometimes of very aiflerent age. In the greater number of cases contact deposits are found at the junction of eruptive and sedimentary

rocki, or between two aeries of eruptive rocks ; while they also, at times, occur at the junction of limestone with other stratified deposits. Where eruptive rooks form one of the walls of the deposit, the intruding rock appears to have left cavities which have snbaequently been filled with mineral ; and, &om the nature of their oconrrence, it will be evident the deposits of ore must necessarily be of a very irregular character.

The cavities do not always occur absolutely at the junction of the two rocks, but may be found at a short distance away on either side of the line of junction ; hence, in prospecting, while it is necessary to drive along the line of junction, short crosscuta at intervals, on either side, are necessary to prove the existence of ore. The remarkable deposits of copper at Monte Catini in Tuscany belong to this class, and are chiefly associated with serpentine ; and the celebrated Oomstock lode was at one time considered to be a contact deposit ; but in its tower levels it passes from one rock to another, so that it ia now regarded as a true fissure vein. It is difficult, however, to understand how a lode from 100 to 200 feet in width could have been opened by the sliding of the hanging wall on the foot wall, unless by successive movements which opened the fissure from time time.

An instance of the occurrence of copper ore at the junction of limestone and elate may be mentioned in the Merces mine in Portugal, where the ore is very rich, contuning as much as 30 per cent of copper and up to 3 ozs. of gold per ton ; but the deposits have hitherto been very irregular and send oflf shoots into the limestone in the upper levels of the mine, and also calcareous veins carrying ore which intersect the slate.

The adjoining sketch Fig. 18.-Stioii. aertion of this deposit will

be of interest as showing how one class of deposit may merge into another (Fig. 18).

The filling of these cavities has in some cases taken place by a segregation of the mineral from one or other of the enclosing rocks; but in other localities the waters carrying the mineral in solution may have come ftom a considerable distance.

Ibbbodlab Dbp0Sit8. 113

Nameronfl other instances of contact deposits might be cited, but it is nnnecBSSary to give further illustrations.

Cave Deposits include all those deposits of mineral which an found in irregular-shaped masses in limestone, and they might be subdivided into chambers or pockets, flats or sheets, and pipe veins. An examination of any of the numerous caves, which occur wherever beds of limestone are found, will give some idea both of the irregularity of the deposits and the way in which the cavities have been formed.

All caves in limestone have been dissolved out by the action of water charged with carbonic acid, but the direction of the drainage of this water is originally determined by the fracture of the rocks, and, in many cases, the size of the cavities has been, greatly increased by mechanical degradation when, as is often the case, rivers have been diverted and Sow through these caves for a greater or less distance. There is a river which, flowing into a limestone cave at Trieste, again comes to the surfiice 10 miles away, having followed a subterranean course for that distance. The Takaka River, in New Zealand, is dry during the summer months for some miles of its course, the water of its upper reaches once more comii to the surface a few miles from the sea in the remarkable Waikaremumu (bubbling water) springs, whence it issues in great volume.

Oaves are extremely irregular in form ; sometimes they open out into huge chambers, several of which are frequently joined one to the other by small passages through which a man can hardly crawl. It is not unusual to find holes in the floor down which streams of water pour to unfathomable depths ; while in others, if a atone be dropped it can be heard striking first on one side and then the other until at last the sound is lost.

These different cavities afford illustrations of the various mineral deposits in limestone, and show how extremely irregular they are. The formation of the cares by solution and the deposition of the ores in the spaces hare sometimes been successive and sometimes concurrent actions. The chambers in which stalaotites and stalagmites are generally found correspond to the socalled chamber deposits and pockets, and the holes Just described afford illustrations of the so-called pipe veins of galena, so largely worked in the carboniferous limestone of Derbyshire.

Lead ores are of moat frequent occurrence in these care deposits; but at Alston Moor, in Cumberland, luematite and calamine have also been found under similar conditions, and calamine is worked at Laurium, in Greece, in cave deposits in limestone. Gold and silver, associated with metallic sulphides, hare olio been found in care deposits in limestone at the Eureka,

114 PBOBPEcnira fob iiiiieral3.

OonBola, and Richmond Mines, Nevada, and at the Flagnlaff Kesaler Cave in Utah. Carbonate of manganese has also been worked under similar conditions at Laa Cabeasea, in France, this being an almost nniqne instance of the occurrence of this mineral in workable quantities.

Borne authors include thee cave deposits under the term of "gash Teins"; bat the olaasification is evidently incorrect, because the first cause of the formation of cave deposits may be due to movement just as well as fracture, and in some cases cave deposits change to tme fissnre lodes in depths when the limestone beds are passed through.

The foregoing brief description of irregular deposits will be sufficient to indicate the general conditions under which minerals of commercial value may occur other than those which prevail in true lodes; but it must be borne in mind that, while the divisions are made, no hard and fast line should be drawn between them, for contact deposits or cave deposits may pass into true fissure veins, and many of the other deposits are frequently associated with lodes of which they are offshoots, thus the description given can only be taken as a guide for the assistance of prospectors in following up what sar&oe indications they may find.

Chapter Viil

EtsrERRiirG to Chapter YI., it will be found that lodes traverse the country in many different directions, and that, in districts which have been carefully studied, those lodes which follow different courses are, as a rule, characterised by special minerals.

It is seldom the case, where more than one system of lodes occur in a district, that the same upheaval which produced one of these systems was instrumental in fracturing the rock in other directions. The lodes are generally described as riEht rtumiog lodea, oross couTBes, and oaimter lodes ; the first term being appUed to the main lodes of the district, whatever their direction; while the cross courses are those which run nearly at right angles to them, and the counter lodes in any other direction.

Faulting of IiOdes. — It will be evident, where each of these systems have been caused by upheavals along different lines,

DTNAJEICa OF LODES. 115

that these npheaTala must have taken place at successive times, and the systems of reefii will be of different ases ; also that the alder systems will be dislocated and, perhaps, displaced by those of later date.

This being the case, in order to follow the rich parts of the lodes with the least amoijut of dead work, study must be made of the geological structure of the district in order to find which ia the oldest system of lodes and hov they have been dislocated, so that the displacements which have taken place ia those lodes which have been intersected by the younger ones be investigated.

In order to clearly explain these displacements it will be well to revert for a moment to the formation of lodes. It is known that, in the majority of cases, these are formed by fractures of the strata which are more or less nearly parallel to the lines along which elevation has taken place. Under these circumstances, where several systems of lodes occur in a district, they must have been formed Ir successive elevations of the country along different lines, and the later formed cracks or fissures would intersect those which had been already made. If, then, a district has been subjected to many such movements, the reefs occurring may present a complete network, and the work of tracing them may be somewhat complex.

It may be accepted, as a rule, that true fissure lodes are never opened so as to form underground drainage channels without a certain amount of movement taking place ; without, in fact, the occurrence of a feult with a greater or less throw — in other words, the formation of a lode necessarily displaces the strata through which the lode passes.

Bearing this in mind, it is evident that when rocks are traversed by a fissure lode the beds on one side of the lode will stand at a higher level than those on the other side ; and, necessarily, if the country be again &ulted along lines which are not parallel to the former lodes, that, in addition to the bed rock being displaced, the reefs which were already formed will be subject to the same movements ; hence we may always be certain that any lode which intersects or displaces another ia the younger of the two.

Belative Age of Faulting, — Having carefully studied these peculiarities of the lodes (and the information required can generally be obtained at ao early period in the history of a mining district), it ia possible to trace with accuracy the order of events in the formation of the lodes, and to decide, ibr instamie, if the KW. lodes displace those striking N.S., or

, Cookie

116 PKOBPEOTIira for KINERAIiS.

are themBelves displaced ; and if the H.E. or N.W, lodea are the oldest or youngest on the field, or are of intermediate age, interseotiiig one ayHtem aod being cut themBelves by the other. Some opinion can thus be formed as to whether the lodes being worked are likely to be &ulted, or will run as master lodes through the district. These main considerations being settled for any particular locality, a study mast next be made of the results which accme in the various lodea, and an endeavour made to lay down laws which will serve as a guide in searching for those lodes which have been cut off by slides or younger intersecting lodes. In order to clearly understand the matter, it will be better to illustrate the various cases with a diagram (Fig. 19) :-

In the foregoing section beds (a) and (e) (which are shown as approximately horizontal, or with only a slight dip) are traversed by reefs (6), (c), (d) which strike and underlay in different directions ; these have been dislocated by a fult Several most important features are illustrated by this section.

In the ,/$raf place, it will be seen that where a fault traverses horizontally-bedded strata, the beds on the hanging wall side of the fault occupy a lower horizon than those on Uie footwall sid&

Dynauicb Op Lodes. 117

Secondly, that the movement tabes place in the direction of

the dip of the fault.

Tk&dlj/, when reefa traversing the strata are dislocated by a. fault it iB eeldom the case that the dislocated lode dips in. such' a direction that, being faulted, will make no apparent difference between the course of the reef on the hanging and footwall aides of the fault. In the majority of cases the dislocated lode will appear to have been subjected to a side movement, as well as an up and down one, this apparent lateral movement being called a " heave " by miners. Jjie diagram will illustrate sufficiently how it is that the reefs appear to be heaved, when they have in reality been only faulted ; but it is necessary to point out that these apparent heaves are sometimes to the right hand and sometimes to the left, and also may be either in the direction of the greater or lesser angle formed by the intersection of the reef and fault. When a elide is intersected in driving along a lode, some laws will be necessary to determine — JWttly, in which direction to search for the lode which has been cut off; and seamdlj/, the probable distance that will have to be driven in order to intersect the lost lode. The first of these questions can be settled in the majority of cases by a rule which will be given by and by ; the latter involves a very accurate knowledge of the geology of the district.

In arriving at a conclusion in the first case, when it is simply desired to know the direction in which to drive for the recovery of the lode, it must be clearly borne in mind that, as already pointed out several times, a slide, cross-course, or lode which intersects the reef that is being worked is, mechanically, nothing more than a fault. This cross-course may be an ore-bearing lode on the one hand, or it may be nothing more than a fissure in the rooks filled with clay, or sometimes it may even be an open watercourse. In any case, however, it is a fault, and in the greater number of cases the hanging wall portion of the country wili have slid downwards upon the footwall portion. As already hown, in describing the section (p, 116), where a fault intersects rearing seams of coal, or reefs standing at a high angle, there will be an apparent lateral heave in one direction or the other.

Iiaw regulating Bireotion of He&Tea. — In the early days of mining these heaves were noticed, and the miners of 300 years ago observed that in the majority of instances where a lode was intersected by a cross-course the heave took place in the direction of the greater angle. In other words, if a drive was being made along the course ot a lode, and a fault was inter-

118 Fbobpbcting Fob Uiitkbalb.

Mcted, SB in the following Bketch plan, the lode would generally be heaved from a to a', or in the direction of the greater angle, It was further known that when it could onee he determined in which direction the lodes of a district were heaved by any aeries of crOBS-couraes, the law might generally be applied to the district in question. Thus, for instance, if it was found that' the lodes were generally heaved to the right hand when they met a crosscourse, it would be said that the district waa one of right-hand heaves. Both of these rules are applicable in a greater or less degree, bat thhave been very thoroughly tested in Cornwall by Mr. Henwood, who has catalogued all the peculiarities of the more important lodes there.

He states that out of 233 intersections of lodes examined, 63, or 22'7 per cent., were not heaved at all; while of the remainder, 150 were heaved in the direction of the greater angle, and 30 in the direction of the lesser angle, 119 being right-hand, and 60 left-hand heaves.

Of those lodes, then, which are heaved by intersecting crossooursea in Cornwall, the following percentages represent their respective directions i —

Fig. SO,— Plan.

Heaved to the right hand, .

Heaved in direction of ereater angle,

It is perfectly evident, then, that these percentages do not afford a satisfactory rule, even in Cornwall where they have been studied, since they only give an approximate notion of the direction in which the heave has taken place. In order to give a definite law for the recovery of lost lodes a rule was devised by Schmidt and Zimmerman, with the result that when applied to the Cornish lodes it was found to be correct in forty-nine cases out of fifty.

STNAHtCS or LODES.

U9

Bohmidt'fl Iaw. — To apply Schmidt's law it is neoeasary to know accurately what is the strike and acderlay of both the lode and ; this can best be determmed by actual Burrey in the mine where two levels have been opened; bat where this is not the case the average strike of the reef and cross-courEe can only be taken in the level being driven, the underlay being determined by the lamb bob or clinometer.

Having, however, arrived, by the best means available, at the true strike and nnderlay of the reef and cross-course, it is next necessary to show these on a plan, the object being to delineate the points of intersection of the lode and at two different levels in the mine, and thus obtain the line of intersection of these two between the different levels. It will be better here Eain to illoatrate the method with a ditram.

It will be seen &om this diagram (Fig. 21) that by means of a survey the exact position of the intersection of the lode and orossconrae can be determined at the different levels, and the line of intersection can thus be delineated on plan as shown. Where, however, the mine has not been opened out on sncceasive levels the course of the lode and „

cross-course can only be taken at the one level to which access can be had

By means, however, of a clinometer and compass the angle and direction of underlay, both of the reef and cross-course, can be taken. In the illustration

Fig. 21.— PUn.

Fig. 22. -Plan.

(Fig. 22) let it be supposed that the lode is underlaying in the direction indicated by the arrow at an angle of 45* from the horizontal, and the cross-course at an angle of 60*.

If, then, any vertical distance is assumed as between the lines ab,cd (Kg. 23), and the underlay of the reef and orosa-courae be drawn as represented hyff, hi, tfie line of intersection can

Iso

be arrived at as followe ; — Drop e/and h k perpendicular to ed, cutting off the difltances/ and k I. Then on the plan (Fig. 24) erect a perpendicular to the lode and another to the crosa- I, a course, and cut off the

" ' , diatance /g from the for-nier

, and Jel from the latter. DraT lines parallel to the lode and crosB-course respectively through ths points g and I ; these will intersect at x, and x y will be the line of intersection. lode is heaved

Kg. 23.— Section.

law may be defined as follows intersected by a cross-course or fault, and the lode either to the right or left, then, in order to find in which direction this heave has taken

Fig. 21. -Pisa. the point a (Fig. 26) on the aide in the following diagram.

place, it is necessary to know the direction of the line of intersection of the two. This being determined, the course of the lode and cross-oourso having been shown on a plan, and the line of intersection also indicated, the determination in which direction the heave has taken place is simple. A perpendicular is erected to the cross-course which the lode is lost, as

Ih line of intersection

produced to b, and then on whichever side of the line a h, the perpendicular a c falls is the direction in which to search for the lost lode. In the case given, a d would be the direction in which to drive.

The following diagrams

show that in some cases

the lode will not be heaved

at all by the cross-course.

Fig. 25.-P1MI. „j,ile in others it may be in

the direction of the greater angle /a <2; and in others in the

direction of the lesser angle fa e.

Dynamics Of Lodes.

The distance to be driTen in either caae c&n only be fonni] when the amount of vertical displacement of the fault is known, and this cannot always be determined. Where accurate plan

Lode loved in direction of lesBer angle. Fig. 26.-Plan.

aud sections of the geoltcal structure of the country traversed by the fault are availaWe, die exact poeitioo of the beds on ither side of the fault may be recogriised ; and, haying th

122 Pbospeotiitq For Minerals.

amount of vertical throw,. the here can easily be determined, since bj setting out the line of intersection in elevation instead of plan, the ratio which exists between the vertical displacement and the heave can readily be arrived at.

Exceptions to Schmidt'B Iiaw. — There are a few cases in which Schmidt's law does not apply, but these are chiefly where subsequent movements have ten place, tUting the fault from its original plane to one dipping in the opposite direction. It will be readily seen that in some cases the movements are very complicated and require most careful study before they can be properly understood.

The following plan will explain what a complicated network might be produced by the successive action of two &altE with their corresponding heaves on a single lode : —

Fig. 37. -Plan.

The lode abode was originally one continuous fissure, and was first of all heaved by the fault x in the direction of the lesser angle ; subsequently, the country was dislocated by the fault y which heaved both the lode and the original crosscourse in the direction of the greater angle, thus giving rise to the somewhat complicated structure apparent in the plan.

A study of this plan illustrates very well the comparative dates of the different dislocations. It will be evident that in the first case the country was broken by elevation parallel to the once continuous line ahcde, and, the fissure being opened in the manner previously described, the channel was filled with ore before the second movement took place. This second move-

Dvitahics Op Lodeb. Is3

meat was an elevation parallel to the line x, and it will be evident, from the way in which the lode is heaved hj it, that the lode and fault x are underlaTing in the direction indicated by the arrows on the plan. The underlay of the fault y muat also be as indicated, and the elevation parallel to the line y must have been the last structural movement which had taken place. Other cases may occur in which a lode is intersected by a cross-course which strikes in the same direction as the lode, bnt underlays in the opposite direction, as below (Fig, 28) ; in cflaes of this sort there will, of course, be no heave apparent, but the bi

lode may be brought

timea by parallel faults.

Some districts are traversed by a great r ber of &ulta of this sort,

and taking Greufell,

New Sonth Wales, as an — -

illustration, the ree&

have been faulted time Fig. 28.-8ection.

after time, so that at present the quartz appears to occur in a

succession ef isolated blocks which are found following a zigzag

line through the couDtry from the surface downwards, the

blocks seldom having a greater extent than about 200 feet.

The lodes in this district occur in a rock which is called porphyrite, consisting of felspar crystals in a felsitic base ; near the surface, and for some hundreds of feet below it, the rock has been decomposed and changed from its original blue colour to a sort of dirty brown. This rock, although hard to work in the mines (requiring the use of explosives), crumbles away rapidly when exposed to the action of the atmosphere ; it traverses the country in a north and south direction, the beds on either side of it to the east and west being slates. In these slates several reefs have been found which run parallel to the main line of upheaval ; hut in no case have they proved to contain a sufficient quantity of gold to pay for extraction. In the belt of porphyrite, however, some very rich reefs have been found ; but instead of running north and south, as in the slates, they traverse the porphyrite obliquely, coursing north-east and south-west and underlay to the norUi-west at angles varying from 56° to 65°.

As already stated, these reefs have been subjected to numerous heaves, and these have generally thrown the reef in the direction of the footwall ; so that a vertical section of one of the mines would be much as shown in the aoining sketch (Fig. 29).

124 Prospecttiko For Hinerals.

In all cases where the reefs have been set back in this maimer the slides which bare dislocated them traverse the coimtry at very flat angles, aad the movement, instead of being a sliding or settling down of that part of the country, which is on the hanging wall side of the reef is repreBentd by the reverse faults which have been previously described. Hence Schmidt's law wonld not be applicable in driving for recovery of the lost lodes. There has, however, been one exception proved to this rnle in the Homeward Bound Claima, where highly payable atone was traced to a depth of 300 feet from the surface. Several floors, such as described, were met with which heaved the reef into the footwall, sometimes for as great a distance aa 26 feet, but at the 300 feet Fig. 29.-SecHon. level the reef jumped for a

distance of 9 feet into the hanging wall, and it is worthy of note that the slide which dislocated the reef at this point traversed the country at a steeper angle and, on its underlay, met the underlay of the reef; so that normal conditions supervened, and the movement which took place was a downirard one on the banging wall side of the slide.

Other instances might, of course, be quoted in which Schmidt's law is not applicable for the recovery of lost lodes, but in by far the greater majority of cases tlie rule is applicable ; the exceptions are only given with the view of explaining why in certain oases it will lead to incorrect conclusions.

n,g,t,7.cbyGOOglC

Chapter Ix.

Allutial Dip0Bit8.

Havihq alluded to all the different conditionB under which minerals occur, either aa reefa or atratified deposits, it is now proposed to devote a chapter to a description of those repositories of minerals known as alluvial deposits. This subject is of the more importance because, although thej are of a less permanent character than reefs, the greater quantity of both tin and gold which has, np to the present time, been won, has been derived from deposits of this sort ; and large areas still exist in which a judicious application of capital on comparatively poor ground will be remunerative. It should be mentioned here that the only minerals of importance which are found in alluvial deposits are gold and the other precioua metals, aa well aa tiostone and the gems which, from their hardness, and their power of resisting chemical change, are preserved in their original state, even when submitted for long period to the action of the weather.

Source of Materials. — It will be evident to all that alluvial deposits have been derived, in the first instance, either from reefa or irregular depoaita, auch as deaoribed, or from rocks which are impregnated with mineral ; and that, in the majority of cases, the tin and gold found in these alluvial depoaita have alao been derived directly from reefs, although it ia probable that the larger nuggets of gold were deposited by chemical or electrical action at the places where they are found.

Ae of Parent Bee&. — Although at one time these alluvial deposits formed part of parent reefa, and have, by the deuudiog and transporting action of water, been broken down and rounded, they were in some cases detached from the reefs at a very early period in the hiatory of the earth, and have since been subjected to the action of water flowing in many different directions y hence, the diacovery of payable alluvial gold may not afford the means of tracing directly the reefs from which thia gold waa derived.

In order to render thia quite clear, it is necessary once more to refer to the rocks in which the reefs occur, and the periods

L26 PHOBFBCTIlta FOB MINERALS.

during which the fisaures were formed that ure now filled with mineral deposits.

A special history necessarily appertains to each individual district, and it is manifestly impossible to deal in these pages with many instances ; but it will be of interest to mention a few as illustrating the class of investigation that may be adopted by the prospector who will take sulficient trouble to study the reasons for the various facts that he observes.

Australian Beefs. — In Yictoria the reefs chiefly occur in Upper Cambrian and Lower Silnrian rocks; while in New South Wales they traverse the beds of the Upper Silurian and Devonian systems. During the Devonian period, or at its close, great upheaTala took place, granite in many places was brought to the surface and the enclosing rocks were fractured along a number of lines, the direction of which depended upon the lines of upheaval of these granites. The fissures formed were charged with mineral, and from that time the formation of alluvial deposits commenced, the rocks themselves being worn away by the action of running water, and the minerals broken the . reefs concentrated in the river channels of that day. There can be no doubt that such was the case, because at the base of the coal measures of New South Wales there are beds of conglomerate in which water-worn gold occurs, and sometimes, as at Tallawong, there is sufficient gold present to make these conglomerates worth working.

Of course, the gold in these conglomerates must have been derived from reefs which existed before the Carboniferous formation (now occupying such a large area in New South Wales) had been deposited ; but, at the same time, there are many reefs in the country which are of much later origin. The Silurian rocks, for instance, are traversed by dykes of diorite, some of which are on such a massive scale as almost to merit the term of bosses, and it has been pointed out by the l&te Mr. Wilkinson that many of these dykes are very closely associated with the <iocurrence of gold.

Dykes of this rock penetrate not only the coal measures, but also the younger Hawkesbary sandstone, so that it is a difficult point to determine the period of their intrusion or even to say whether they are due to one or a series of eruptions. Be that as it may, however, it is perfectly certain that at some places the reefs are due to the intrusion of rocks of this class, and a study of the alluvial deposits in these districts gives uamistakable evidence of the fact that the gold was derived direct from the parent reeC

Alluvial Deposits. 127

A visit to some of these localities, or even an inspection of a map on which the reefs and gold leads aro delineated, is convinoing of the fact that the alluvial deposits have been derived directly from the reefs. The streams in which the alluvial deposits occur cross the belts of country in which the reefs are found, and it is only those parts of the streams which now lie below the line of reef that payable gold has been obtained. This distribution of the gold not only points to the fact that it has been derived directly from the reefe, but also shows conclusively that the drainage system of the country has not been changed since the alluvial deposits began to be formed.

But this is not always the case ; for, in other localities, very great changes have ensued since the earliest deposition of the

fold-bearing gravels. For instance, it has been pointed out by [r. Wilkinson that at Biragambil, New South Wales, there is a gully in which payable alluvial deposits occurred that have since been worked out, the gold of which could only have been derived from the auriferous conglomerates of the coal measures ; these conglomerates were denuded and their gold concentrated by a process of natural sluicing. The proof that this is the case is to be found in the &ct that above a certain point in the gully, a joint at which the coal measures cease, and Silurian slates are met with, no gold has yet been found ; nor are the conditions of the slates such as are favourable for the o

Deep Leads. — There are also some other and most important alluvial drifts in the Gulgong district, which have not been deposited by existing streams, these drifts being known as the deep leads; they are found at considerable depths below the Bur&ce of the ground, and are frequently buried beneath as much as 100 feet of basalt. Similar conditions prevail in Victoria and New England, New South Wales.

These gravels were deposited by streams which, flowing during Miocene and older Pliocene times, had a somewhat different course from those which flow at the present day, and their course was suddenly arrested during the middle Pliocene period by streams of molten rock, which, flowing from fissures opened in the surface of the ground, poured down some of the watercourses and dammed back the water in others, up which they flowed until they found their level. The magnitude of this eruption can be appreciated when it is remembered that in New South Wales around Armidale the granites and other rocks (which had been, since the Devonian period, subjected to the eroding action of water, and had been out by it

128 Prospectiito Tos Hiniralr,

into a number of guUiea aad gorges) were once more levelled off and oonrerted into & table land, all the irregnlaritieB being filled up by this molten rock.

It has been suggested by Mr. Norman Taylor that it was in some way due to the effect of this basaltic eruption that the occurrenoe of diamond in the older drifts of Galgong can be traced. There are many interesting places in this neighbourhood in which there is much difficulty in accounting for the manner in which the gold drifts were brought to their present position. Amongst others the Canadian and Whitehorse claims may be mentioned, in both of which the auriferous gravels now lie at a much lower level than any of the surrounding country, being, in fact, deposited in a depression. It is true that both these deposits, which adjoin one another, are resting on limestone and, indeed, are found in cavities in the limestone itself; hence, one is led to the conclusion that the river which deposited this gold very probably had an underground course for some distance, in which case a lead of gold may yet be traced through caves of limestone which mark the former course of the river.

These deep leads have since, at times, been again cut through by streams, which have in places even cat gorges through the basalt, and the earlier deposits have been once more concentrated by the action of running water.

Hew Zealand Beefs and. Deposits. — In New Zealand the conditions have been very different to those which prevailed on the Australian Continent. It is true that auriferous reefs are found traversing Lawer Silurian beds, as in Victoria, and Upper Silurian beds, as in New South Wales; but they also intersect both Upper Devonian and Lower Carboniferous rocks, which in this country consist chieEy of slates, sandstones, and breccias. The lower Secomry rocks which overlie these beds are .not traversed by ree&, so that probably the date of the formation of the ree& was anterior to the deposition of these beds. There is, however, no absolute proof that this is the case, for the earliest known alluvial deposits in New Zealand are those known as the cement workings of Cement Town, near Reefton, which are of Cretaceous age ; they belong to the coal measures of the colony, which, as already pointed out, are Cretaceous.

All that is known for certain of the period of formation of the ree& Is that they were formed after the close of the Carboniferous period, and before the commencement of the Cretaceous period. There is ample evidence in support of this, for alluvial gold, more or less rich, is somewhat widely distributed on the west

ILLirVI&L DEPOSITS. 129

coast of the South Island in rocks of Cretaceous age ; while some very rich deposits of recent date are due to a natural concentration of these gravels.

As an illustration, the Mangles River, a branch of the Buller Kiver, may be taken, in which some very rich alluvial wai worked near the junction. This gold was generally coarse near the lower part of the river ; and a aimilar class of gold was worked as high as Macgregors on the Tiraumea, at which place the oonglomerates of the ooal measures cease and the head waters of the Mangles flow through granite and slate. It is a remarkable fact that above this point, although there is still a certain amount of alluvial gold obtained, it is in far less quantity, and is much finer than obtained lower down; so that no doubt can exist as to the rocks from which the coarse gold has been derived. Much time has been spent unprofltably by miners in prospecting these Cretaceous coal measures for reefs, it having apparently been overlooked that the gold was probably derived from the conglomerates and simply concentrated, and that the rocks are not such as would be likely to contain ree&.

Later again in the geological history of New Zealand, in fact, during the Upper Miocene period, the land stood at a much higher elevation than at present, and continental conditions, with lat rivers, prevailed. During this time the course of the rivers was more nearly north and south than now. The Buller River instead of flowing into the sea at "Westport, as at present, delivered itself into Golden Bay near Kelson; the Aorere flowed at a higher level and drained to what is now the month of the Farapara ; while other large rivers flowed north and south along the west coast, carrying large quantities of shingle with them and dxisiting thick beds of gravel with small quantities of gold. Remains of these old terrace deposits yet exist; indeed beds of gravel, frequently over 300 feet thick, occur, which have since

crossBtreamsnowflowing i° -°lW°Vt;1-

alluvial deposits have -—' -:-

These alluvial deposits are represented in the following

section (Fig. 30), the wash generally being found on blue marly clays of Tertiary age, which are spoken of by miners as "false bottom." Alluvial

deposits have aIeo been formed by the denuding aotion of water on reeia In recent times j those whicii occur on the main or slate bottom are of this order.

The alluvial deposits of Australia and "Sow Zealand may thus be grouped as follows : —

Carboniferona conglo me rates.

Mt. Poola ! .

Deep leads of Miocene and Pliocene

Pleistocene and recent leads

main bottom. Black sand beaches.

No parallel.

Cementa of Cretaceous age. Miocene gravels of West CoasC, oaiy suitable for hydraulic slulc-

Recent alluvial deposlM on false

bottom. Recent leads on main bottom.

The beach deposits of New Zealand are almost unique in their occurrence, for, although gold occurs to some extent in similar beds in Australia and elsewhere, they have neTer been of the importance of those in New Zealand. All along the west coast a heavy current sets to the northward, which during heavy souerly gales is yet stronger. Wherever beaches exist which are exposed to this northerly current there are deposits of alluvial gold found near low-water mark, mixed with black sand. These depoaibi are worked by means of a portable sluicing table, which is wheeled down to the edge of the sea at low water, a flexible hose being rolled down after it. It ia found that after every storm the gold in the sand is renewed. Sometimes the men who own these claims have to wait as much as six months for their deposit of gold to be renewed ; but, even under these conditions, they are reported to make good wages at their work. The lack leads, which have yielded large quantities of gold, have been formed in the same way, bat, since their deposition, have been removed beyond the of the waves by an elevation of the land.

AUavlal Deposits of British Columbia. — Special atteutioa has been devoted to a description of the Australasian alluvial dosite, because they illustrate nearly every condition which can prevail ; but it may be well to allude to British Columbia aa affording an illustration on a gigantic scale and exhibiting features which are perhaps better studied there than elsewhere This mounttunous country affords evidence throughout of the important part glacial action has played in shaping its ranges

Alluvial Deposits. 131

and forming its lakes. Moraines of great size are found and, in addition to this, the hills are covered over large areas by a glacial till which is sometimes of very great thickness. The "till" carries gold in greater or less quantities, and has been washed hj hydraulic power at places where it has been found to carry sufficient gold to make it remunerative. At the present time a good deal of attention is being devoted to testing these deposits, and large areas, as yet untouched, will no doubt be worked in the future. But where these deposits of " till " have been oat through by recent streams, the process of resluicing, already described, has concentrated the gold, and some of the richest alluvial drifts have been formed which have yielded most phenomenal returns. Williams Creek, for instance, in tha Cariboo district yielded $20,000,000 in the early days, and many other (although not so rich) deposits have also been worked. The occurrence of rich alluvial deposits under thes* conditions has, of course, led to prospecting for reefs in the vicinity, but hitherto without much success. It will be selfevident that this is another instance in which the alluvial gold has travelled for some distance from its parent reef, but that, having been transported for the first part of its journey by ice, it has not been greatly worn, hence an inspection of the gold itself would not give any idea of the distance it had travelled.

The following are a few of the conditions which have to be considered in the determination of the value of alluvial deposits. It will be evident that gold may be found under any of the following conditions : —

1. In the beds of rivers ; either with shingle in the stream, or as beaches, or in pockets or ledges on the solid rock.

2. Under a cover of a few feet of shingle or surface soil, which may be stripped by band.

3. As leads below many feet of cover, in which case the grotind has to be worked by means of shafts, and the lead

4. As poor deposits scattered through large quantities of gravel, in which cose the whole deposit has to be sluiced on a laive scale.

As regards the two first classes of deposits it is unnecessary to make any further remarks, except to point out that a study of them, and the peooliarities of the rivers which have deposited them, may serve as a guide in following the leads in the third class of deposits.

Gold is deposited by rivers at all points where the current ia checked by any means ; thus, during; floods, when the section of

1S2

Frqspectino Fob Hihirals.

a river is as follows (Fig. 31), gold is thrownup on the banks, and small beaohea are left when the river &lls, which can frequently be worked by such simple methods as cradling ; but leads have been formed in the main course of the river, and follow the direction in which the main body of the river

This being the case, a

careful study should be

made of everything which

causes any change in the direction of e. river. The following

sketch illustrates this, and gives a fair idea of the manner in

which beaches are formed, and gold renewed in these beaches

from time to time when

the river is flooded.

The principal current would flow down the centre of the course so long as no obstructions were encountered; bat when any bins' was met, the direction of the current

would be changed

and pass from one side of

the stream to the other,

to be once more deflected

on meeting a blaS* on the

other side of the river.

Not only this, but when a

Fig. 32.— Pln. river ia cutting its bank on

one side, it is continually

depositing shingle on the other, the section of the stream being

The auriferous deposits will, therefore, be formed in the slack water on the shallow aide of the stream, and the leads of gold will follow much straighter lines than the regular course of the stream which deposited them, and, moreover, will not be uniformly rich along the lead.

It is evident that where a close idea can be formed of the former direction of the stream which deposited the leads of gold, much information may be gleaned as to the direction which the richer parts of the leads will take ; but unfortunately it is often the case that the surface ban been so changed since the deposition

Ogits. 133

of these deep leads as to moke it almost impossible to arrive at Batisfactory conclusions. It is only after the leads have been irorked that the former course of the river ctut be traced.

In those depoeits, which come under ClasB 4, no attention

J'ig. 33.— Section, whatever is paid to the distribution of leads of gold ; but the whole body of wash is sluiced away on a face, the profits being dependent upon the enormous quantity of material moved. It is chiefly in America that operations of this sort have been carried on, where, on the slopes of the Bocky Mountains, large claims are worked to treat wash dirt from 100 to 200 feet in thickness, in which, it ie stated in official reports, aa small a return as 2id. per cubic yard will pay. In cases of this sort there are, of course, several faces opened up for sluicing, and the quantity of water brought in is enormous, while, necessarily, all other conditions must be of a favourable character to enable these low grade deposits to pay dividends on the capital involved. It will be of interest to call attention to the salient points in any such scheme, in order to affoid the prospector the opportunity of gauging the chances of success.

Necessarily, the first consideration is the quantity of gold present in the drifts, and the thickness and extent of these drifts themselves. This question should be gauged at the outset by sinking shafts through the drift, and cradling or hand-sluicing everything that is raised from the shafts. By these means the best idea can be obtained of the average yield of the drifts.

When the yield is high, other conditions are of comparatively

little importance; but when low every other feature must be considered in forming an estimate. The quantity of water available must be gauged and the cost estimated of bringing this on to the property ; and seeing that the pressure obtainable is an imporbint point, a careful survey will be required to see at what altitude the water chd be brought on to the claim. This survey u of the more importance, because by it the only feir estimate can be made of the coat of the race, the amount and lieigbt of fluming, where it is advisable to use siphons, and a hundred other small points, all of which bear upon the value of the ground.

The next most important feature, after the value of the gravel and quantity of water have been determined, is what facilities exist of disposing of tailings, or, in techniiMl terms, " what dump exists." This is of great importance, and involves several considerations. When the deposit to be sluiced is situated high up on ranges above the river level, especially if a stretch of unoccupied ground exists between the claim and the river, no possible difficulty can exist ; but this is not always the case. Difficulties may arise, either from there not being sufficient &11, or from farmers or others occupying the lower lying ground and objecting to the tailings being deposited Upon their property. This haa formed so important a matter in the United States as to necessitate an Act of Congress (known as the Debris Act) restricting owners from depositing tailings, except under arrangement, and compelling them to impound them in settling areas when required, and only to allow the clean water to escape.

The difficulty of impounding is not so very serious in the matter of additional cost if a sufficient bead of water is available, for by the use of hydraulic elevators the tailings can be raised to 10 or 16 per cent, of the height representing the pressure of water available. When this pressure, however, cannot be obtained the absence of dumping ground will make an otherwise valuable property of no value at all. Even when the tailings can be dealt with by elevators the initial cost of the undertaking is considerably increased if they have to be employed.

Some very extensive operations are conducted at times with the object of recovering the gold in the beds of live rivers, and very often the results achieved are not commensurate with the expenditure. The methods adopted vary a good deal, according, to the nature of the river ; thus, for instance, on the Molyneux Kiver, in Kew Zealand, dredging has been very successfully

Alluviai. Dbpobits. 135

adopted, backet dredge being employed, and the material dredged sluiced on the barge. The tailingB in modem dredges are <£spo!ied of by bucket elevators at the stern of the barge, and are thus deposited at a greater elevation than the sur&ce of the water; the dredging channel being kept clear. Similar operations are being proposed on the Fraser River in British Columbia. The success of these operations depends to a very large extent upon the facility 'with which the dredges can he moored, the dangers from rapid rising of the river, and the manner in which operations are conducted. When other conditions ore favourable, very low grade gravel will pay for dredging, bat it is difficult — indeed, impossible — to estimate what the yield of a river bed will be, except by means of a dredging plant, so that the expense of a dredge has to be incurrwl for the purpose of prospecting. It is true that some idea may be gained by testing the river bed at low water, or even by running out wing dams. Testa are olao made by divers, and occasionally by bore holes; but these can never be relied upon OS giving accurate results. Hence some speculation must always attend the first operations in dredging a river. Dredges are now largely used for washing the beaches which flank streams, and also for dealing with alluvial deposits which are at some distance from existing rivers, for wherever an excavation can be made in which sufficient water will accumulate to float a dredge these machines can he employed. The cheapness with which dredges are operated makes them well adapted for treating very low grade gravels. In other cases a river it diverted, and its original bed laid dry; and in others again, by the construction of crate dams down the centre of the stream, and the deflection of the river to one or other side, one-half of the river bed at a time is rendered available for sluicing operations. Great danger exists in these cases from floods, sjid it is by no means on unusual thing for the work of months to be carried away in a night, many promising enterprises having thus been brought to an untimely end.

Alluvial deposits, it will be seen, include forms of mining which vary from the moat primitive methods of washing with a tin dish, cradling or hand sluicing, to operations which involve the expenditure of large quantities of capital, and tax the energies of the beat hydraulic engineers to bring them to a successful issue.

n,g,t,7.cbyGOOglC

Chapter X.

Roblk Mbtau.

Gold— Platinum — Osctiiim — Itidtnm — PftUadium — TdUuiinm.

DlBtribation. — Gold is more universally disseminated in nature than is generally supposed, although there are only a few fields in the Trorld where it ia abundant South Africa is now the largest producer, with a field of over millions of ounces of gold for 1898, Australasia being next, and California third on the list.

Its general mode of occurrence is, like platinum, in the native state ; but, unlike that rare metal, gold is found in association with many ores, especially sulphides. Gold occurs in actual combination with tellurium only ; there are tellurides of gold, of gold and silver, gold and lead, i&c.

Uode of Deteotion. — There is very little difficulty in recognising gold, although, many curious mistakes are made by men who have had no experience, specks of capper pyrites in quartz and even small yellow flakes of mica being at times taken for the precious metal. Gold, however, remains of the same colour in every light, is metallic, and can be cut with the point of a knife i whereas, other minerals are brittle ; moreover, it is not affected by acid other than nitro-muriatic add. The prospector, however, soon gets so well acquainted with its appearance as to hardly ever make a mistake ; if the stone be crushed and washed, the gold will be very readily recognised in a tin dish in which, if any doubt exists, it can be amalgamated with a little mercury.

AsBooiation with Sulphides. — Although gold is almost universally present in iron pyrites, it is not, in most cases at

Koble Uxtalb. 137

ftoy rate, in actual combination with sulphur ; but is only disseminated through the pyrites in the metallic state, or intercalated in minute scales between the crystalline layers of that mineral. Oold is also found mixed with copper pyrites, galena, zinc blende, miBpickel, stibnite, magnetic pyrites, and cinnabar, all of which are sulphides. It is often found in company with native bismuth, magnetic iron, hiematite, barytes, apatite, fluorspar, and siderite; but its most universal matrix is quartz, although calcite or dolomite more rarely form the gangue.

Auriferous Belts. — The moat usual mode of occurrence ol gold is in reefs, from which alluvial deposits are derived. In the richest and most celebrated gold-mining districts these reefa do not occur singly, but in belts. The ree& in the two most important mining distriots of Victoria at Ballarat and Sandhurst, which lie to the south and north of the dividing range respectively, form two well marked mineral belts. In Hew Sonth Wales there is an important, though net so well marked, belt which extends north and south of Bathurst ; and in California the whole of the auriferous veins of the Sierra Nevada can be considered as a great auriferous belt.

In each of these cases the main trend of the belts is north and south ; but there are many anriferons reefs occurring in them which strike in other directions, especially east and west, or at right angles to the principal veins, and these are called crossveins or cross-courses. In Victoria the number of cross reefs is probably not one-tenth of the total number of "reefs known, but in New South Wales they are of more frequent occurrence.

It is important to study the course of the greater number of reefs in any district, because the dispersion of gold in alluvia is most abundaut in regions where the drainage system corresponds with their strike, rivers flowing at right angles across the general direction of the reefs not having abraded ibem over so extensive a.a area.

Occurrence of Beeft. — Auriferous veins occur most frequently either in or associated with eruptive rocks of various ages from Tertiary to much more ancient times.

Of those which traverse eruptive rocks themselves, the gold- Itearing reefs of S.E. Hungary may be mentioned. They intersect a rock called "propylite," an altered variety of andesite, which is also the enclosing rock of the Comstock lode, and is found again associated with the tufaceous rocks in which the auriferous ree& of the Thames in New Zealand occur.

In the Ural Mountains gold-bearing reefs also occur in eruptive rocks. In the district of BerezowE, in the Southern Urals, crystalline schists have been traversed by dykes of a fine-grained

variety of granite, parallel in strike with the direction of the mountain chain. This variety of granite, eapecially when it is in contact with the lodes, contains iron pyrites altered and docomposed to limonite. At right angles to the dykes innumerable quartz veins occur, from 1 inch to 3 feet wide, containing gold, iron pyrites, &c., but they have not proved very remunerative. Qold also occurs in the same district in quartz veins traversing diorites, serpentines, &c.

In the Australasian Oolonies, again, as in other parts of the world, eruptive rocks are frequent associates of gold-bearing veins, being sometimes traversed by them, but in other cases are found alongside the auriferous reefs, which thus occur as junction deposits, an interesting illustration of which is seen at the Wentworth goldfield, near Orange, in New South Wales, where the gold seems to be partly held in solution by mispickel, from which it exudes when heated in the shape of moss-like excrescences {Liveraidge, Traiu. Hoyai Soe., N.S. W., 1876).

According to the late Mr. G. B. Wilkinson, the auriferous deposits occur at the junction of serpentine with a felspathic rock containing hornblende (bomblendic feUite), which in some places passes into diorite (sections examined microscopically by Mr. C. J. Alford show this rock to be a magma basalt). Along this line of junction is the "lode," which, at the surface, is a fissure 6 feet or more in width, extending nearly N.W. and 8.E. for a distance of 60 chains. It is filled with a sandy ferruginous clay containing hard siliceous accretions of irregular shape, locally termed " clinkers." It underlays to the N.E. at about 66°, Uiough in some places it is nearly vertical. The horublendic felsite forms the footwall, and the serpentine the banging wall.

Shoots, — In the felsite at varying distances along the " lode " are quartz veins from a few inches to 6 feet thick, coming in from the west and abutting against the lode, which they appear to follow down, forming irregular quartz "pipes" or ''shoots," which dip diagonally in the lode towards the east. These veins have only been found to contain payable gold when they junction with the "lode"and form shoots (also called "bonanzas").

Mr. A. R. Canning, writing in May, 1898, says — "Along the outcrop of the 'joint' after the removal of the recent alluvial some twenty apparently distinct lodes were discovered. Some of these were not more than 60 to 60 feet apart, others lay several hundred feet away from the next. About 3000 feet divided the most south-easterly from the'extreme north-westerly body. Most of these veins on reaching the contact joint overflowed along it in a south-easterly direction, and, the gold for the

hull, .. A''."->'ll-'

Noble Hetaub. 139

most part existing in this overflow, tbe early miners on the field regarded the contact joint as the main channe], and the anriferouB body found ong it was known as ' the lode.' "

A careful ezamiiiBtioD of this district, and a study of the workings of the different mines on the Wentworth goldfield, demonstrates the fact that the serpentine, which forms the hanging wall of the so-oalled " lode," fills a fissure itself between diorite walls, being at some places only a few feet and at others some hundreds of feet in width. It is only on the footwall side of the serpentine that gold has as yet been found, and there only where the quartz reefs which traverse the diorite abut against the serpentine. It ia a remarkable fact, moreover, that where these reefa approach the serpentine they gradoaily change from quartz to calcite, which latter mineral carries the gold, ohiefly, where nndecomposed, in mispickel.

Other contact deposits are numerous, but amongst others it may be mentioned that at Rodna, in S.E. Hungary, gold and silver occur with sulphides in a vein of calcspar and quartz in a contact deposit. The country consists of mica schist, hornblende schist, granular limestone, and Tertiary deposits, traversed by dykes of andesite. When these come in contact with the limestone the ore deposits occur.

Again, in the Eureka district, Nevada, a great ore channel extends along the eastern base of Prospect Mountain for a ditaoce of 12 miles. This appears to be a contact deposit in beds of limestone, quartzite, shale, &c. The ore contains gold, silver, and lead, and some of the mines have yielded a considerable return in bullion.

By far the greater number of reels, however, traverse sedementary rocks, and in Victoria, where careful observations have been made and records kept, the auriferous quartz veins which traverse the lower Silurian rocks are considered to be richer than those which occur in the upper Silurian ; those in the lower Silurian also strike more nearly north and south than those in the upper part of the system. Gross reefs striking east and west are comparatively rare.

The reefs in New South Wales are generally smaller and richer than those in Victoria, They occur mostly in the upper Silurian and Devonian systems, and cross reefs are more frequent than in Victoria.

One of the most remarkable gold veins in California ia the great mother lode, which extends for a distance of over 70 miles, with a tbicknessvaryingfrom 6 feet to over 60 feet. Insomeplaoesitoutcrops like an immense white wall, bnt ia not always remunerative.

140 PROaPEfTTINO FOR UIHEBALS.

Alth.ongh perhaps the moat importaat gold-bearing reefa belong to the fissure type, which have been described in pre- Tious pages, there are many localities where important reefs occur which belong to different types.

Bedded TelnB.The Tta Madre in Mexico is a vein coinciding with the strata, and is considered to be a bedded vein, the dip of both the lode and rocks being about i5°. It attains at sooie places a thickness of 150 yards, and occurs at the junction of clay slates and conglomerates which are supposed to be, the former, of Devonian, and the latter, of Triossic age. The veinstone is amethyst quartz with calcspar, enclosing fragments of the country rock. Gold, silver, and silver glance are the principal ores ; but numerous other minerals occur, including the common sulphides.

In cases of this sort where ore deposits are, for a part of their course, regularly inters tratified between the beds, it is difficult to avoid using the term " bed " to describe them ; and, indeed, it is quite possible that such deposits may in some cases have been formed as beds in a similar manner to the banket beds of the Transvaal already described. When the term " bedded veins " is employed it must be understood that their formation is attributed to the same origin as that of true veiua, and that they have not been formed contemporaneously with the strata in which they are enclosed.

Saddle BeefB. — A cUss of reefs not hitherto described in these pages, which are called "saddle reefs," occur at Sandhurst, Victoria. Fig. 34 gives an idea of their shape, and also suggests that they may have been formed at the intersection of a parallel system of fractures with cross-joints in the rocks ; they may, however, be due to foldings in the strata.

The richest parts are said to be at the caps of these reefs ; the branches (which are called the eastern and western legs respectively) being relatively poor, although generally one of these legs will pay to work for some distance down, while the other is barren. Many of these saddles are found one below the other, as shown in the sketch ; they are only developed by sinking.

It is not in Sandhurst only that reefs of carved shape occur ; at Cluues, for instance, there are several saddle reefs. Fig. 35 shows the shape of one of them, which seems to be a vein of segregation in the folds of an anticline to the west, and of a syncline to the east. The alluvial wash here is covered by 81 feet of gravel, 142 feet of basalt, and 15 feet of surface soil.

Plat Veins. — Tn Gippsland there are some interesting veins of segregation which are illustrated by the accompanying sketch.

Noble Hetals.

They are called "flat veins," and occur in dykea of. diorito porphyty, which, for a certain depth from the surface, ar decomposed to clay. The quartz is very rich in the soft, decom-

Fig. 31.— Section.

posed matrix, but when the undecomposed rock is reached' in depth, the quartz appears to become poor, or to run out.

rig 35.— Section. Fig. 36.— Section.

Breooia IiOde. — Before oonclnding this branch of the subject

there are some exceptional modes of occuireiice of gold which

should be described. The first of these is at Browns Greek

mine near Blayney, Kew South Wales, described as an ii

breccia lode, in which the gold ie disseminated ia fine particles. The vein stuff ia a ferruginous flinty rock, with concretions of chalcedouy and the country rock ia limestone penetrated by dykes of grey diorite. It has been stated that this deposit shows evidence of segregation or deposition from hot springs which probably accompanied the diorite eruption.

The Wentworth field aSbrds an illustration of the influence exerted by cross veins in determining the dip of shoots of gold, but in many other localities, cBpecially where the rocka are dipping at moderate angles, and are of different degrees of hardness, the rich parts of the lode will be determined by the intersection of the lode and a belt of congenial or "kindly " country. It is of the greatest importance to discover the laws which govern the distribution of the rich parts in reefs, and the caases which have influenced the dip of the "pay shoots." Although the laws which have been enunciated in the chapter on fissure lodes will not always explain all the peculiarities of a, field, they will form the basis on which to work; and, when considered in conjunction with any local peculiarities which may exist, will generally give valuable results. A careful record of the work in a mine, showing, in addition to the direction of the levels, the distribution of the rich parts worked, and any changes ia the rooks, or intersections of veins, will afford most valuable hints as to the direction which future workings should take. These details unfortunately are seldom shown on the plans of

Gold also occurs disseminated through rocks sometimes aa native gold, but more frequently associated with various sulphides. The banket beds of the Transvaal have been already described, and a similar class of deposit have been proved to exist in the Tarkwa district of West Africa.

In Brazil, gold occurs under exceptional circumstances in beds of metamorphic sandstone, which is sometimes flexible, containing mica, micaceous iron, and other minerals, and forming lenticular masses in a formation which is supposed to belong to the Lower Silurian or Cambrian period. This sandstone, which is called " itacolmite," not only contains gold, but also diamonds, rutile, tourmaline, &c. The gold is always alloyed with silver and copper, and sometimes with platinum. It is also found in a rock called itabirite, known locally as jacotinga.

At Borsa-Binya, besides some trachyte, there is a peculiar labradorite rock, called timazite or hornblende andesite, which traverses both the mica schists and Carpathian sandstone. A whole mountain is formed of this timazite, in which a certain

Noble Hbtal 143

nnmbei' of veins occur nearl; parallel to one another. Copper pjrriteB and iron pyrites, with little quartz, compose the filling of these lodes, and are both anriferous, and iron pyrites is also disse minuted through the timazite.

Another remarkable deposit which occurs at Belubula, New South Wales, has already been described in the chapter on stratified deposiM ; but the most remarkable deposit of all is that of Mount Morgan in Queensland of which the following description by Mr. E. L. Jack published shortly after its discovery is of interest.

The summit of Mount Moian was composed of what Mr, Jack calls a sinter deposit, and he says, in bis report on the district: — "Down the hill sides to the north, west, and south a similar deposit is everywhere met with; a frothy or spongy matrix, sometimes aluminous and sometimes siliceous, generally ironstained and occasionally associated with large masses of red and brown hsmatite, but gold has as yet only been obtained from a few places away from the hill top, although, naturally, there haii been vigorous prospecting (so far as possible in an nausually dry season) wherever the 'formation' resembled that of Mount Morgan."

In describing the deposit he says : — " The frothy and cavernous condition of the siliceous sinter of Mount Morgan may be accounted for by the escape of steam, while the silica was yet (after its deposition on the evaporation of the water) in the gelatinous condition so frequently observed in the deposits of hot springs. The aluminous silicates represent the familiar outbursts and flows of mud. The iron oxide appears to have been deposited in some cases along with the sUica and alumina, and in others to have been deposited later, its solvent fluid having been, as it were, injected into the interstices, vesicles, and caverns of the silica and alumina. In some oases it may have been originally pyrites, as it now and then occurs in cubical hollows. Calcareous sinter is very common in siliceous springs and iti absence from Monnt Morgan must needs imply the local absence of limestones among the rocks from which the spring was fed. The silica would be found abundantly in the quartsites, and the alumina may have come in part from a deepseated underlying granite. The gold, and to some extent the iron, may have been dissolved out of the iron pyrites of such reefs as the'Mundio Beef seen in Mundic Creek; the gold possibly by chlorine produced by the contact of hydrochloric acid, derived from tJie decomposition of chlorides, with manganese, which occurs sparingly in the form of pyrolnsite along with the ironstone of Monnt Morgan,"

PSOBPBCTIKQ rOS HINBBALS.

It ia doubtful whether Mr, Jack was correct in hia viewa regarding the origin of this deposit ; for a lode deoompoeing near the sar&ce, especially if highly charged with pyrites, would present very similar phenomena, and later developments have demonstrated the pyritic nature of the lower levels, the pyrites being associated with quartz (see also p. 104).

Gold in Deep Leads. — The occurrence and distribution of gold, &c., in alluvial deposits has formed the subject matter of another chapter, bat a few remarks may be added on deep alluvial deposits.

It should be borne in mind that in those places where deep alluvial loads have been covered by flows of basalt they have had the best chance of resisting denudation, and it is to the protection thus afforded that the deep leads of Australia owe their preservation. It is evident that such leads are not likely to exist in flat country ; but will generally occur either on the slopes or at the foot of high ranges. In many cases where the alloyia of the valleys have been thus buried and protected, the rivers have been compelled to cue fresh channels for themselves.

Most of the deep leads of Victoria have been buried in this way, and at Ballarat there are no less than four distinct beds of basalt, below each of which a bed of auriferous drift occurs. These different flows of basalt are known as the first, second, third, and fourth rocks respectively, and they are represented in the following sections, taken from Brough Smyth's AuttTlian Ooldfields, 1869;—

Hoble Uetals. 145

In the following section taken from the same work, a valley hae been formed by denudation of the drift. On one side of the valley the drift is overlain by basalt, but is uncovered on the slope of the opposite bank (Fig. ""'

Denudation has frequently worn away the beds, so as to leave hills capped with bafialt, as on the slopes of the Sierra Nevada. The gravels seldom lie on a flat bed rock, but generally on a concave, basinlike Bur&ce, the edges of which are, in California, called "rim rock," the term " bed rock " being reserved for the bottom of the depression. Tail races, or sludge channels, are frequently driven through this " rim rock " in order to work the low-lying parts of the drift, as in the section (Fig. 39).

FUTIHDH AND AlLIBS McTALS.

Flatinutn, the least fusible of the metals, occnra in alluvial deposits in small grains, together with sbme other very rare metals such as osmium, iridium, and palladium. It is often found with gold, as in the Urala, which district produces nearly all the platinum used in the World. In other countries it oocnr* in relatively small quantities, as in New Zealand and

FROBPECTIKO TOR HIHKB&La.

Kew Bontli Walei ; and a fair quantity has been found in some parta of Califomia, altbongh no steady yield haa been obtained there, probably due to a large extent, to the fluctuations in ralne making ue search for it seldom remtinerative.

In New South Wales, a nugget of 268 grains — over half an onnoe — is reported to have been found, at Wisenuui's Creek, with alluTial gold ; but it was no doubt Tery impure, having a specific gravity between 16 and 16 only.

Although of comparatively little importance, some of the metals usually associated may be mentioned. Iridosmine, especially, ia stated to occur commonly with alluvial gold in New South Wales, usually in minute grains or scales, and it ia also mentioned from N'ew Zealand.

It may be remarked in connection with these minerals that platiniridinm and iridosmine are even heavier than platinum itself, as seen in the table ; and that they are at the same time the hardest metals, being as hard as quartz ; so that they are easily distinguished from platinum, which is malleable, and of the same specific gravity as gold. Platinum has never been mined except in alluvial deposits, but &om its association in the Urals with chrome iron and Terpentine, it is inferred that, in this country at least, it occurs in serpentine. In the neighbourhood of Broken Hill, New South Wales, it hati been found associated with a lode, but has not been worked.

Table

Op Noble Metals.

innml.

Cokm.

Bemuit.

Electrniu, .

Gold with

Very pale

yellow

Mallesble and

ductile.

Gold, .

Always with ilver, ftc.

I6 6-1B4

the most ductile of all the metali.

Pt with It,

4-S

Steelywhite

Millesble when

pd, *o.

pore.

Pt,Ir

White

Iridonniae, .

Tin-white

or lead-

Malleable with

difficulty.

Pd with Pt

.Sh

and If

Pi. pUti

num. /t.

riding

iim.. Pd.

Noble Ubtal3,

Tellnrinm is tiie ouly metal which has hitherto been found in natare in actual chemical combination with gold. It also occura in a native state, and, combined with other metala, forming tellurides.

The moat important of these are included in the following table, but tellurides of mercury, bismuth, lead, and nickel also exiat: —

Table Of Tellurium Mineeals.

Hiiunl.

par

Hwduau.

Streak.

Native

Smalt gold

Tin-white, Tery fusible, buma with a greenish f Ume — very

Te, An, Pb

AnQ

Blaobish lead-

Lead 'grey, very fuaible, givea a blue colour to

grey

tbe flame— rare.

Heuite, .

Te,Ag

able— race.

Petzito, .

Te.Au.Ag

Item-

Sometimes tarnished.

Sj'lTaiiite

TAu,Ag

Steel-

Steel-grey, Beotile, give* the flame

Agll

gray to

ailver-

a gTMniah-blue

white

Calaverite,

Te, Au

An 40 Ag 3

"

Yellow-

Mawive, bronzeyellow, brittle, blnieli. green

grey

flame.

Te, Tellnriumi Au, Gold; Ag, Silver; Pb, Lead.

The most common of these minerals, petzite and sy Ivanite, are of fairly common occurrence in Colorado, more especially at Cripple Creek ; in the gold and silver mines of Transylvania ; an({ more recently, they have been discovered in considerable quantity in the Hannans or Kalgoorlie District of Western Australia. In this last-mentioned locality they are found,

accompanied by pyritea and forming the permanent ore, in depth below the zone of deoom position near the surface.

Above this line of decomposition, some very rich fermginoiu quartz lodes occur, and the gold is very fine — in some cases looking like mustard disseminated throagb the matrix, and only exhibiting its metallic lustre when banished.

Tellurides constitnte exceedingly valuable ores when they are sufQcieatly rich to allow of hand picking and Bale to smelters, And even the poorer ores can be treated by roasting and either ohlorination or cyanidation. In many cases attempts to concentrate have been uaBatisfactory, as the mineral frequently slimes A great deal ; bat concentration is said to have been suocessfdlly applied in Bonlder County, Colorado, and the possibility depends to & great extent upon the nature of the ore.

Specimens are found in many localities, bat it is in comparatively few places that workable deposits exist.

Chapter Xl

flILTER AHD LEAD.

SiLTEB ocoura under two very different conditions ; the first aa silver minerals or ores, the second as ores of lead or copper in which more or less silver is present.

Aa the simplest means of extracting silver is by smelting with lead ores and desilverising the lead thus obtained, it is obvioaa that when no lead is contained in the ore itself it will be necessary either to mix lead ores with it, if smelting is to be resorted to; or else adopt a different method of treatment. Those silver-bearing lodea which do not contain lead are spobea of aa " dry ores."

It will be seen that the ores of the first class may be directly recognised, either by their appearance or blowpipe oharactera j whUst the second class will only disclose to assay whether or no they contain silver in sufficient quantity to be of value.

The silver ores proper all yield a bead of silver when treated before the blowpipe, on charcoal, with carbonate of sonia; the most common of tbem are given in the following table ; —

Bilteb Aud Lead,

TABLE OP aiLVEE OEES.

Mineral.

Beumka.

Native Silver,

Shiidng

Perfec'tiy'seoiile, crysUkusaaUj

S

Co 317.

BUoi

Deep lead-grey.

Stembeite.

Fb

Do.

Rare — givoa a inftgnetio globule from prea.

Stephuiito sulphide,

S,Sb

Shining

Tabular ctyatali, iron-blaet.

S, Sb, Aa

Co 10°/.

BUck

Do.

Pyiiniyrite,.

S,Sb

Red

Dark raby.Mlver.

S.As

Do.

7B

fl-4

Shining

/ProducCa of decomposition

Br

Yellow, iab-occurring

generaUyincruata.

lodareyritB, . Embollte, .

J

yC

/ coating, and oaulifl War-

a, Br

Yellow

like oxoreor

green

I in minute ory-

S, Sulphur J F

,Iron; Cu

Coppori Sb, Antimony; A>, Araenic; Ci, Chlorine;

Br,

Sromine

/,Io.

line.

The preliminary examination with the blowpipe having determined that a mineral belongs to this group, it is practicable in some oases to decide b; simple inspection which of the foregoing minerals it is; but in others it is necessary to apply certain tests in order to discriminate between them, and the following notes will be of service : —

ITatiTe Silver not likely to he mistaken for anything else, its malleability and white characteristic colour being sufficient for its determination. It will be distinguished from platinum by being fusible before the blowpipe, while platinum is not. It might be confounded with one of the native silver amalgams, but tese are rare. One of these, called "amalgam," contains

about 30 per cent, of silrer, is brittle and generally is found either maBsive or as coatings ; while another, called " arquerite," contains 86 per cent, of Bilver and is malleable. It often occurs in orystala, whilst native silver is generally found in strings, branches, or dendritic crystals. Iativa silver has never been worked in alluvial, and is not likely to be found in this kind of deposit ; although its occurrence is not impossible.

Argentite is fairly abundant and, being of great value, is ioiportaut to recognise. Its surface is usually tarnished, but it may be out like lead and then appears of a bright lead colour. It is so easily fusible that it will melt if brought near to the flame of a candle. Grey copper, especially when tamisbed black, might be mistaken for silver glance as it has the same external appearance, but, in addition to the characters already mentioned, sUver glance will not give antimoniaJ fumes, nor the smell of garlic due to arsenic before the blowpipe. There is also a great difierence in weight, the specific gravity of argentite being about 7, whilst that of grey copper is about 5.

Some cobalt ores will be distiuguisbed from silver glance in that they are more or less brittle, at least not malleable or sectile; infusible in the flame of a candle; and yield a blue bead with borax before the blowpipe.

To distinguish silver glance from copper glance or boamonite the blowpipe reduction assay on charcoal with soda is necessary, as they are both easily seethe and fusible ; the first will give a silver, the second a copper bead. This distinction, however, will be made before the mineral is included in this group.

Btromeyerine. — The lustre and colour of cupriferous sulphide of silver are the same as those of bournonite and some grey copper ores ; but these will emit white fumes and a smell of garlic before the blowpipe, while stromeyerine will not. This mineral, however, may be difficult to distinguish on account of the presence of copper, and an assay may be necessary.

8tephanit, being brittle, will be easily distinguished from silver glance, which is sectile. Prom black oxide of copper it will be distinguished by the reduction of the metal on charcoal with carbonate of soda, and from polybasite by the of arsenic.

Pyrargyrite and Prouatite, the two ruby-silver ores, will be distinguished froia one another by their streak, that of pronstite being lighter in colour, and by their different behaviour before the blowpipe ; pyrargyrite yields fumes of antimony, pronstite the smell of garlic. They are each, hoW' ever, liable to be confounded with other ores.

When cryBtallieed they resemble epecular iron or hBmatite, but may be easily diatiiiguished ; for iron ores will not melt before the blowpipe alone, while the silver ores will, and ate same time emit the charaoteristic fume. Another ready teat will be that of hardness, specular iron being scratched witb difficulty by a knife, while the ulver ores yield easily to it. Specular iron also becomes m&gnetio on oharooal before the blowpipe. From oopper glance they will be distingnished by the colour of the streak, as also from polybasite.

When compact the niby-silver ores sometimes resemble realgar, oiniiabar, and red oxide of copper in appearance, but will be distinguished by the colour of the streak, which is cochineal-red for ruby silver, orange for realgar, scarlet-red for cinnabar, and brown-red for oxide of copper ; the distinction from cinnabar, however, will be doubtful

Before the blowpipe cinnabar entirely disappears, as it is composed of sulphur and mercury, botb,of which are volatile.

Pyrargyrite occurs sometimes of a lead-grey colour, when it resembles silver glance, copper glance, and Doamonite ; but the streak will in all cases be sufficient to remove any doubt.

Eerargyrite, or horn silver, presents the appearance of wax, and is as readily cut; so will be easily recognised. The newlyoat face soon tarnishes and becomes greyish-violet on exposure to light. Bubbed on wet iron, zinc, or copper, bom silver yields a coating of silver, and blocks of ia mineral sawn through with a steel saw show silver coatings on either faoe-

BTOmargyrite is similar in character, but is generally of various shades of green.

lodargyrite is oilen earthy and yellow, and, consequently, TMembles some earthy oxides, such as those of lead, bison antimony, and molybdenum ; but these always accompany the metals from the alteration of which they are formed. The blow> pipe test will ascertain the nature of the yellow powder.

The study and discrimination of silver ores is very important, forgot only are they interesting in consequence of their value, but several compounds in which silver exists are not easily recognised. As it often happens that a small quantity of a silver mineral, disseminated in grains through an ore, is sufBcient ' to make that ore very valuable, it ia most desirable for the prospector to thoroughly accustom himself to the recognition of such minerals ; as a failure in this respect may result in his missing a valuable discovery.

As an illustration, it may be mentioned that small grains of argentiferous mispickel occur disseminated through some galenas.

15S PROBFECTlNa FOH UIKBRAL8.

which are, in consequence, very rich ; and it is alao well known that silver chloride in l&rffe proportions is often found in an earthjr matrix which would generally be disregarded. Such is the case with the rich chlorides of sUver scarcely risible in the o-alled " pacos " and " colorados " of Peru, and in the gossan at the ontorops of many silTer-bearing lodes.

Valuing BUver Ores. — Native silver often occurs accompanying other silver ores, and is sometimes sufficiently abandant to form its most valuable constituent, as at Kongsberg, in Sweden, and in Peru. Argentite or silver glance, which is the sulphide of silver, ia perhaps the most important of the ores of this class ; but the antimonial silver ores also occur in considerable abundance in certain locaJities, notably in some of the American mines. The chlorides and chlorobromides of silrei are also, at times, of importance ; but as they are essentially ores of decomposition, are seldom found at any great depth from the surface. In the gossan of many silver-bearing lodes they are abundant and of great value, and are also at times found disseminated through andesitic and rhyolitic rocks, as in the Calico District of Oifomia.

A simple, but rough, method is sometimes adopted of testing the value of ores from day to day when chlorides are the minerals chiefly worked — viz., by powdering the ore in the mine, mixing it with a solution of hyposulphite of lime, which dissolves the chloride, and then Etdding sodium sulphide, which forms a dark-coloured precipitate if much silver is present. It is evidently impossible to estimate in this way the contents of silver, but it afibrds a very good test whether the ore is of value or not.

Some rich silver ores are very brittle, especially those containing antimony and arsenic, and great care is necessary in the process of taking average samples, or iinreliable results will bo arrived at. Care is also necessary in working the ores on a large scale to see that all the dust produced ia saved for treatment, as this is frequently the richest part of the ore.

Many silver deposits in America, along the Cordillera (both to the north and south), and in Europe, especially in Transylvania, are connected with some peculiar kinds of eruptive rocks belonging to the group of andesitea, and spoken of as propylites. This rock occurs at the famous Comstock lode in Nevada, where not less than a dozen varieties of eruptive rocks, andesites, propylites. Sic, belonging to three different epochs of eruption, form the accompaniment of this rich deposit. A better opportunity could not be selected for again directing the attention of prospectors to the important connection which mar be observed

Bilter And Lead. 163

between the eruptive rocks and their metalliferoua contents, and to the importance of studyinK their connection carefully. It may be added that some of these deposits are of very recent origin, as the rocks of the andesitic family have been chiefly erupted during tertiary times.

The silver ores of the second class mentioned at the beginning of this chapter are those which occasioDally carry silver, and then come under the class of argentiferous ores. These may be enumerated as follows

Boumomte (snlpho-antimonide of lead and copper). See Copper.

Tetrahedrite (antimonial grey copper). See Copper.

Tennantite (arsenical grey copper). See Copp&r.

The above minerals, when argentiferous, do not give evidence of the presence of silver, unless they are submitted to the process of assay. A very simple test for the presence of silver in ores, however, is mentioned in Charles H. Aaron's PractietU Treatiie on TeHing and Working Silver Oreg, and is as follows; — "The ore should be ground fine, and then a few ounces are mixed with about one-tenth of its weight of salt, and one-twentieth of copperas. This is placed in an old frying pan, and heated gently BO long as a smell of burning sulphur can be noticed, the mass being stir'ed with a thin bar of iron all the time. Air ail the sulphur Las been driven oS, the beat is increased for a few minutes to a light red, and the mass stirred until it swells up and becomes sticky, care being taken not to fuse the ore. The mass is then taken out, and allowed to cool on a rock, aud after a little more salt has been added, and the ore mixed with water to the oonsifltency of mortar, a atrip of sheet copper, previously cleaned, is inserted, and left there for ten minutes. The copper is then removed, washed in clean water, and if any silver ia present, it will be coated with a white substance, which will be heavier or lighter, according to the richness of the ore, and, if very rich, will appear grey and rough. The frying pan should be smeared with clay or mud, and dried before being used."

Silver exists in traces, or in larger proportions, in all galenas ; but an assay is the only way to ascertain the percentage, as there is no physical character to distinguish the poor from the rich argentiferous galenas. It has often been stated that galenas with small crystalline facets, like coarse lump sugar, are rich in silver, while those with large cleavages are poor ; but

1S4 PBOSPECriKO roR kink&ls.

this character at beat is only loctil, for some galenai with large cubical cleavagM yield as much as 1,500 oza. of ailver per ton, whilst other fine-grained ores contaia 50 ozs. per toa, or eyen less.

ArgentiferoDB grey copper and galena, accompanied by the different arsenical and antimonial silver ores, form the chief characteristic of the silver mines of Saxony and Bohemia.

Lead Obes.

All ores of lead give a bead of metallic lead when heated on

charcoal with soda before the blowpipe. They will be readily

distinguished one from the other by the ofaaracters given in the

following table : —

Table

Of Lead Oees.

c™,

atroit

a, G&Iena, .

Sulphide

Lead-grey.

Glide

DuU-yellow or

bright red.

e, Cerufisite, .

Carbonate

White or greyish.

rf, Anglesite, .

Sulphate

White, gily, or Mack.

Chromate

e

Oranire yellow.

Phosphate 4

7a

S!-l

White or

pfiite.

chloride

yellowish.

ff.Mimetite, .

Arfleniate

3J

Light yelbw.

Bmiarhe.—a, Metallio lead-grey ; cubical cleavages or granular, b. Not common, found with galena; orange-yellow to red. e. White to grey; decrepitates and fuses, d, Not common, e. Colour red ; blackens and fuses when heated. /, VarionB colours, yellow, red, and green ; swell* np and changes colour when heated, g, Loatre adamantine; generally covered with a black coating of arsenic ; faces of crystals curved.

Lead mioing in Europe is inseparable from silver mining, as silver is mostly extracted from argentiferous galena ; cheap labour and scientific appliances enabling poor ores, containing only 9 or 10 ozs. of silver per ton, to be treated at a profit, both lead and silver being extracted.

In America, where the prodoction of silver is enormous, the proportion of galena mined to silver ores proper is relatively small, and the economic conditions are not so favourable to

8Ilveb And Lead. 155

a large production of lead, a metal of comparatively little

QaleDa.— Galena ie found in abundance throughout Australia, but up to the present time only those ores which are rich in fiilrer have received much attention. The immense deposits of comparatively poor ores, however, of which the best illustration is to be found in the Broken Hill mines, are being worked, and doubtless as time goes on, and still more economical applianMs than those now in use are introduced, still poorer ores will be worked.

The most troublesome feature about the Broken Hill ores has been the association of zlncblende with the galena, more especially because the silver is associated with each mineral, so that no process of concentration is of value in enriching the ore. A very ingenious process was devised by Mr. Ashcroft for dealing with this class of ore which worked perfectly eatisfiictorily experimentally, but was not financially satisfactory on a large scale. A brief description of the process may be of interest The mixed ore, consisting of galena and blende, is first roasted so as to desulphurise a portion of the blende, leaving an amount which is determined by circumstances still nu&fiected. The roasted ore is then leached with ferric chloride, the zinc being dissolved as chloride, leaving the silver behind and the iron taking the place of the zinc as hydrate. The zinc is subsequently precipitated by electricity, an iron anode being employed, and the ferric chloride is thus renewed. The galena together with the hydrate of iron and what zinc has not been dealt with, is smelted and the silver and lead saved together in the ordinary way.

N'umerous processes have been tried for treating these mixed sulphides of lead and zinc, but without any marked success. The process devised by Messrs. Sulman & Ficard of briquetting the roasted ore with bituminous coal and distilling the zinc from the briquettes in the ordinary way appears, however, to have been worked for some time on a commercial scale. In this process the lead and silver, after distillation of the zinc, remain in the retort, in & metallic state, entangled in the cte of the briquettes, from which it is subsequently recovered.

Galena, or sulphide of lead, is the principal ore of lead, and the permanent ore in depth ; but at the outcrops of lodes several other minerals, mentioned in the table, which are products of decomposition, are found. These are the oxidised ores, such as carbonate, sulphate, phosphate, arseniate, and, more rarely, molybdate and chromate of lead. The combiaationa of lead

luuile

166 PHOBPEOTItia roR uinebals.

with chlorine (except as pyromorphite) are very rare, aad so kIso is the oxide.

Aitbough carbonate, araeniate, and phosphate of lead are of very frequent occurrence in galena lodes, their are seldom Bofficieiitly abandant to be considered as regul&r ores, except in the upper workings before the water level is reaobed, below which galena is to be expected as the permanent ore.

As galena is often accompanied bj iron and copper pyrites, there is generally a gossan on the back of the lode in which crystals of carbonate of lead, mostly as white tables or needles, are found in the rugs and crevices.

Carbonate of Uead, — Carbonate of lead is not only found crystallised, but alio in earthy masses of a yellowish or oohreous colour, and may be readily distinguished by its weight. When occurring in this form, it is usually mixed with earthy substances and oxide of iron, bat if a specimen is broken carbonate of lead in a pure state will generally be found in the centre, and be recognised by its bright vitreous or adamantine lustre.

Ijeadantimony Ores, — There are several compounds of lead with antimony, but they are never sufficiently plentiful to considered as ores. One of these, jamesonite, contains small proportions of iron, copper, zinc, and bismuth. It occurs in grey fibrous mass or small prisms, and is found in Oomwall associated with quartz and boumonite. Another of these compounds, zinkenite, resembles stibnite and boumonite and occurs in an antimony mine in the Hartz.

Boumonite. — Boumonite, which is spoken of in the chapter on Copper Ores, is a compound of lead, copper, and antimony. It occasionally forms mineral deposits itself, as, for instance, in Colombia, South America.

Xiead Iiodes. — The ores most commonly found associated with galena in lodes are zincblende, iron and copper pyrites, and arsenical iron or mispickeL

The matrix or vein stuff generally associated with lead is either quartz, Suor spar, or barytes.

Lead ores mostly occur in lodes, while copper occurs most frequently in contact veins ; but lead also occurs in contact veins, and, more rarely, in masses in sedimentary deposits, especially limestone.

The best illustration of regular lodes is to be found in the lead and silver veins of the Hartz, Saxony, and Bohemia, which have an extremely regular structure. A plan of these lodes bows the veins and cross-veins belonging to different systems of fracture and filling, arranged with the regularity of a mosaic

Silveb Amd Lead. 157

and in the vein itself the ores and their accompanying gangue are arranged with such order and regularity from the walla to the oeutre, that the name of " ribbon veins " or " banded veins " baa been applied to them. As a rule, the poiats of the crystals are turned towards the interior of the fieaure, and in consequence they are sometimes called "combed veins." The adjoining sketch represents the section of a vein at Frzibram, Bohemia, the different numbers referring to the different bands of ore.

Fig. 40.— Section.— 1, CuinE or oooutrv rock; 2, Flacan; 3, Quartz,- 4, Iron pvritea ; S, Caldts ; 6, Quftrts and baTTtea ; 7, Ziooblende and gslena.

Lodes of this sort afford evidence of very slow deposition from waters carrying the mineral matters in solution. This has allowed the ores and minerals to orystallise beautifully, sections of the veins showing plainly the order in which the various minerals were deposited, the oldest deposits coating the walls of the lodes, the youngest being found at the centre.

This Iwnded structure is almost peculiar to lead and silver lodes; but some deposits of copper, iron, manganese, zinc, &e., are also found in "combed veins. As already stated, lead ores also at times occur as "contact deposits," most of the silver lead mines worked in the centre of France, on the boundaries of the granitic region called the central plateau, occurring under these conditions.

1&amp;&amp; Pbobpectiho Fob

In the neighbourhood of Pontgibaud the country is compoaed of granite, mica achista, and gneiaa, and the lodes are in grajiite. Nnmeroiia dykes of porphyry crop out at the surface, and tho Tn stuff is a kind of granite differing but little irom the country rock and much decomposed at the sur&ice, involving a heavy expense in timbering. The ore is disseminated through the granitic matrix in veins, strings, or irregular masses, or in fine grains.

The galena is generally accompanied by a little zincblenda and pyrites, while grey copper and barytes oocasiooally occur in some of these contact veins, but are replaced by quartz in depth; others contain fluor spar.

Shoots. — The ore forms chimneys or shoots rarely more than 150 feet to 250 feet in length, but permanent in depth.

Other similar deposits occur in the granitic chain of Forez ; most of them in gneiss, but some in granite. One of these in granite is formed of two small leaders, which ocossionally join together. The associated minerals are the same— viz., blende and pyrites ; the vein stuff is quartz with a little heavy apar, and the ore occurs under nearly the same conditiona as those just described in irregular pockets or ahoots.

In the same region other contact deposits (of similar composition) occur in granite, mountain limestone, or sandstone, sometimes at the contact of porphyry.

Chapter Xii.

QUICKfllLVKK OB UEBCDRf.

Cinnab or sulphide of mercury is the only regular and valuable ore of this metal. It is of a bright red to brownish-black colour, is always red in powder, and affords fumes of quicksilver when heated with soda on charcoal. Native mercury and amalgam also occur. Some grey copper or tetrahedrite yields mercury. Tests for Cinnabar.— Cinnabar is very easily scratched with a knife, affording a deep red streak, and before the blowpipe it volatilises, giving off a strong odour of burning sulphur; mixed with dry carbonate of soda and heated over a candle flame, in an iron spoon, it gives off vapour of mercury, which may be condensed on a gold coin held half-an-inch above the mixture. The surface of the coin appears whitish at first, but when rubbed between the fingers becomes brilliantly amalgamated; with care this teat easily detects 1 percent, of cinnabar in

QUICKSILVER OB UBRCUfiT. 159

&I1 ore; the mercury is remoTed &oin the coin by gentle heating. Blowpipe tests disUoguish cinnabar irom all red minerals.

KatlTe MerouTT in a pure state is rarely found, but occurs disseminated in liquid globules in cavities in the cinnabarbearing rocks, especially at or near the surface. It is easily recognised, and a rock suspected to contain metallic mercury may be tested by simply heatiug it as described above, but without the addition of carbonate of soda.

Cinnabar Deposits. — Cinnabar occurs in the Palatinate aa lodes, and impregnations which have penetrated rom the lodes, in strata of Carboniferous age, and in the eruptive rocks which traverse them — viz., porphyry, melaphyre, and amygdaloid. These deposits are nearly exhausted.

At Idria, Austria, cinnabar is found in impregnated beds and stockworks in bituminous shales, dolomitio sandstones, and limestone breccias of Triassic age, dipping 30° to 40°, and covered by Carboniferous sandstones and shales in a reversed positioa. This deposit baa been worked for nearly 400 years, and is aaid to become richer as the depth increases.

The quicksilver deposits at Almaden, in Spain, have been mined still longer, for in the time of Pliny 10,000 lbs. were sent annually to Some from these mines. They occur in upper Silurian slates, sometimes interstratified with beds of limestone; but rarely in the ordinary slates, which are much contorted. The enclosing rock usually oonsista of black carbonaceous slates and quartzites alternating with schists and fine-grained sandstones.

These bed-like deposits incline, near the surface, at an angle of about 66°, and then dip almost vertically. They consist principally of quartz with either granular or compact cinnabar, which permeates the mass generally, and is concentrated in pockets and bunches; while the clefts and cavities by which the deposit is traversed often contain native mercury. Veins of cinnabar occur in the neighbourhood and also eruptive rocks, diorites, with which the deposit seems to have some relation.

At Monte Amiata, in Italy, cinnabu deposits are associated vith munmulitic limestone iich, in that district, rests unconformably on Cretaceous rocks. The cinnabar occurs in veins of calcite, which intersect a fine-grained aigillaceons limestone ; it also permeates the clays along lines of fault. It is more plentiful at the upper and lower surfaces of the nummulitio limestone than elsewhere, but has a widespread sur&ce distribution. A large quantity of mercury is extracted annually.

The quicksilver-bearing belt of Cattfornia extends along the

luuile

160 PROBPBCTIITQ ¥0a HINBRALS.

coast range for a dietance of &bout 300 miles. Their general mode of occurrence is thus described in a report by M. Gr, Rolland {Ann. det Mine*).

" These deposits are generally impregnations in the Oretaceons

and Tertiary fonaations ; they seem to be richer when the beds

ire more sohiatose and transmuted ; they are more or less closely

relation with serpentines which are themselves sometimes

.pregnated. The cinnabar is mostly found in talcose and clay schists, often decomposed and impregnated with oxide of iron, sometimes in quartzose schists, in sandstones, more rarely in limestone rocks, limestone breccias, &c. Native mercury is found in some magnesian rocks near the surface. There are no defined fissures nor veins proper. The cinnabar with quartz, pyrites, and bituminous substances is sometimes disseminated in the rock in line particles and spots, sometimes forms certain kinds of stockworka or reticulated veins and nests. The parts thus impregnated congregate and form rich zones, the size of which occasionally reach 80 fathoms, and the percentage 35 per cent., and flat-like Teins or lenticular deposits, the strike and dip of which agree with those of the schists of the country generally. These rich zones without defined limits gradually merge into poor stuff containing half a unit per cent., or mere traces, and are of no value."

Sulphur Bank, one of the principal mines, was originally worked as a enlphur deposit. Sulphur in workable quantities is known to exist in some volcanic countries, and volcanic rocks are abundant at the Califomian cinnabar mines.

The author previously quoted remarks that a trachytic lava, probably of postEocene age (Tertiary) is quarried for the cinnabar with which it is impregnated, and adds : — " Some geyserites (siliceons deposits from geysers) and some modem deposits, calcareous or siliceous, of concretionary form, and produced by old hydrothermal springs, are coloured by cinnabar. Lastly, there are actually geysers and hot springs which deposit cinnabar."

He quotes the Steamboat Springs, Nevada ; the Iceland Geyser ; the Ohaeawai Springs in New Zealand ; and the Sol&tara of Fuzzuoli, near Naples. At the Steamboat Springs the percentage, though very low, ia not so low as to be neglected, and a deposit of cinnabar which is being worked, and is, at the same time, in process of formation, can be seen there.

In a very interesting paper published in the Tranaaetiorta oj the IntUtution of Mining and Mttallwgy, vol. iv., Mr. James Mootear says, in speaking of the Mexican deposits, " It would seem

Quicksiltbb Or Ubboubt. 161

MS if the general line of the Oalifomian deposits was oontinaed through uie Mezicaa mountain ranges, but there seems also to be another line of deposits extending in a direction north-east and south-west." He also says, "It is foond that there are very considerable difietenoes to be met with both as regards the character of the quicksilver deposits themselves and the nature of the associated rocks; but it is abundantly clear that the deposits have in all cases resulted from the action of mineral springs. There can scarcely be a doubt that these were hot spriogB similar in character to those now in action in California and New Zealand."

In Queensland, at Kilkivan, near Gympie, cinnabar ooours in lodes of calcite, and sometimes of oiucite and quartz. These have not been worked yet on an industrial scale, so that little con be said erf their extent in depth ; but it may be concluded from the few known occurrences in the world that quicksilver is, of all ores, the most likely to impregnate large belts of country'.

Cinnabar has been found in alluvial deposits in New South Wales, and also at Waipori, in New Zealand ; in the latter place it occurs as rolled fragments in the wash.

One of the most interesting localities in New South Wales is on the Oudgegong Biver, near Bylstone, and has been described by the late Mr. 0. 8. Wilkinson as follow! : — " Perhaps the most important feature connected with the occurrence of the ore is that the solid cinnabar is sometimes seen to gradually merge into, or impregnate, the clay or drift of the deposit in which it is found. This is, then, direct evidence that it has not been drifted by making water, like the water-worn pebbles and other material forming the old tertiary lead ; but that it has probably been derived from thermal waters which issued irom the underlying Devonian rocks, and permeated the tertiary deposit."

Deposits are traced by the occnrrenoe of red grains of cinnabar in alluvia; those cannot be confounded with red hematite nor red oxide of copper if the blowpipe is nsed. As to the appearance of the ore, it is very variable, and it will be useful to quote the Tarieties of colour it assumes at Idria, and the names by which the different clasBeB are distinguished by the miners there.

StBhlers (steel ore) contains 75 per cent, of mercury, and occurs in a compact or fine granular form.

Leberen (liver ore) is compact and lustrous, usually forming nests in the stahlere.

ZiegelerE (brick ore) is sandy, granular, and of a bright red oolour.

In all the aboTe-mentioned deposits, cinnabar is found in connection 'with rocks impregaated with carbonaceous or bituminoQH matter, and in every cue where deposits have been worked upon an extensive scale, there is evidence of great volcanic disturbances, which have Apparently been the cause of the deposition during the solfatara stage of eruption.

Annual Produce of Heronry. — The aunoal output of mercury for the world is stated to be about 100,000 flasks of 76-5 lbs. each, and Spain produces about one-half of this.

Payable Orades. — To give some idea of the grade of ore that is payable, it may be mentioned that the New Almaden mine paid {267,478 in dividends on mining 22,615 tons of ore yielding 2-02 per cent., and $53,611 on mining 25,584 tons of ore yielding 1-22 per cent, of mercury, but, of course, the conditions vary in every different locality. At the Oomacchino mine, in Italy, where labour is very cheap, a substantial profit is made by treating ore which only contains 0'6 per cent, of mercury. The average price of quicksilver is about £G, 10s. per flask, but is now quoted at about X8, l&s. per flask.

Table Of Mercury Ores.

Bard-

Str™k

Cinnabar, .

Sulphide oi Mercury

Native

Si

Red

Volatilewhen heated and yielda meronry with carbonate of

Volatile when heated.

Chapter Xiil

Copper.

The minerals and ores of copper are generally easy to recognise in consequence of their very conspicuous colours ; they are also the most commonly known, both for the above reason and also on account of their frequent occurrence.

General Charaoters of Copper Ores. — All copper minerals, with carbonate of soda on charcoal, yield before the blowpipe a

Copfeb. 163

bead of copper, which aometimeB contains iron. They impart a green colour to the flame, and colour the borax bead green. Id nitric acid they give a green eolution, which becomes azure blue when ammonia ia added ; and metallic copper will be deposited on iron in a nitric acid solution.

ClasBifloation of Copper Ores. — They may be sabdtvided into those ores in which copper is in combination with sulphar, arsenic, or antimony alone ; and those which a are classified in the two following tables : —

Table Of Unoxidised Copper Ores.

S&quot;

Copper

screak.

Remuki.

Native copper, Chaloopyrite, .

Bornite or erubescite,

grey copper,

Tennantite, .

Covellite,

copper glance, Bouniomt, .

AnrenideB of copper,

Stannine,

S,Fe

S, Fe

a, Sb, Ab,

Zn,Fe,Ag,

Hg

S, As, Fe

Sb,S, Pb 41 7„

8,Sn

a -8

a-8

Shining

Qreenisbblack

Black

Dark

brown

black Reddish-

bS

Black Black

Dark

grey

Black

Metallic and ductile.

Purple, crystals

Streak dark red; when rich in zino mineral; grey.

Crystallised or

massive.

Indigo bine. Very eaaily soctile.

Before blowpipe

grey malleable

Take's silvery polish ; tainiBhes on eTcpoflure.

?n, Zino ; Pb, Lead ;

Prospecting Fok Minerals.

Table Op Oxidised Copper Ores.

Ulntral!.

Composition.

Copper

Hinl.

Spsdae GrsTltr-

Oxide

Black

[Taoally earthy, BoiUng the fin.

Cuprite,

Glide

Ss

red,

streak

often covered withmalachite.

Blue

Crnits and

m wate'r.

Azoribt,

Carbonate

Aznreblue

Often In radiated orygtallied

Malachite, .

Carbonate

Emerald green

Often mammUlated and fib-

Pliosphate

Green,

SmaU crvatalB, Burfaoe dark.

greenisliyellow

Atscamite, .

Dark olive

green

Crystallised, fib-

Arseniktet of

Green

copper.

tallised.

Silicate

Greener

Crusts and coatings.

Dioptase, .

SUioate

S

Emerald

green

CrystalliBad; rare.

ZTatlTe copper, in the celebrated oopper region of Lake Superior, in Korth America,, forma tbe regular ore of the mines. It occurs in grains of all sizes, and ocoaBionally in huge masses of over a hundred tons in weight, in beds of conglomerate, alternating with trappean rock.

Copper Ores, — Copper pyrites or chalcopyrite is the most emmon ore in nearly all the copper deposits of the would, while bine and green carbonates, in crystals, concretions, or impregnations are the surface ores formed bj the decomposition of cojr pyrites and other ores of copper,

Copper also occurs combined with sulphur as bornite or

purple copper ore ; redruthite, or copper glance ; and tetrahediite or grey copper. These generally accomputy copper pyrites, being more or less abundant, and Bometimes become the principal ore in the lode, as, for instance, purple copper in Tuscany, grey copper in Germany, and copper glance in Siberia and New Zealand.

The carbonates are accompanied near the surface by other oxidised ores, such as cuprite or red oxide of copper, melaoonite or black oxide of copper, as well as the phosphates, arseniates, silicates, and oxychloride. Of these, cuprite and melaconite are the moat important, and sometimes form the permanent ore of mines to a considerable depth.

These oxidised surface ores are usually mixed with hydrous oxide of iron or gossan forming the cap oi the lode.

To understand the occurrence of gossan in the upper parts of a lode, it must be borne in mind that copper pyrites and purple ore are sulphides of copper and iron The surface waters which percolate through the rocks remove the sulphur and copper as sulphate of copper, leaving the iron in the form of a more or less spongy and honey-bombed mass, which is called "gossan." It is consequently easy to anticipate from the nature of a gossan if the ore lying below is likely to be a rich compact copper ore, or whether it is mostly composed of iron pyrites carrying little or no copper. In the first instance the large percentage of copper which has been removed must have left the iron in a very porous condition ; while in the latter the gossan will generally be more compact.

Copper pyrites is not generally found pure immediately below the gossan, but a richer ore, commonly called " black ore, which has no special mineralogical name, is first met with. It is black and earthy, like manganese or black copper ore, but, if broken, nesta of copper pyrites will generally be found in the centre, and the ore passes from black to yellow through intermediate shades of bronze.

What is called "peacock ore" is only copper pyrites coated with oxide and exhibiting iridescent colours. By leaving a piece of clean yellow copper pyrites in water for some time it will become coated in this way.

The easy decomposition of copper ore under the influences of the atmosphere explains why the waters at some copper mines are quite unfit to drink. It is well known that tools abandoned for a time in old workings become covered with a coating of metallic copper, as if they had been left in a bath of sulphate of copper.

Native copper in copper lodes is also & product of deoomposition of Bolpliides, and is often found as platea, when deposited on tie Bide of a cavity or fissure j or as ramified cryatals, when deposited in a soft clay,

Sweats for Copper Ores. — The various copper minerals ennmerated in the tables may be distinguished in the following inanner, a bead of copper having first been obtained from the specimen before the blowpipe ; —

The Bead of Ooppek contains Ihoh, and is THEBBroBB

ATTRACTED BY THE MaONBT,

a. Colour of mineral, gold-yellow ; sometimes iridescent on surface. Copper pyrites.

6. Colour, black on surface j fracture shows the colour of copper pyrites in the interior. Black ore.

c. Colour, violet or between copper-red and reddish-brown, Erubescite.

d. Colour, ateel or lead-grey, or iron-black.

OPey Coppep, before the blowpipe, yield abundant fame of antimony. SDlphnr ii always present, Mtd -emc u sometime* detected.

Tennantlte.-dour of garlic due to arsenic is prominent, and solphnr also present.

The Bead or Copper is hgt attracted bt the Magnet.

1. Luttre metallic, semi-melallie, t

a. Colour, indigo blue ; lustre, not quite metallic ; more nearly resinous when crystallised, and resinous or dull when massive. OovelUte or uuUgo copper.

6. Colour, iron or steol-grey ; lustre, metallic.

BedPUthlte. before blowpipe, is very fusible, and yields a amell of sul-

Boumonite is easily fusible, and emits white fames due to antimony. MelaCOnlte is infusible. 2. LuilTt non-Tnetallic.

a. Colour, black ; earthy, soils the fingers. Molexioiiite.

b. Colour, cochineal red ; dust, brown-red. Cuprite. e. Colour, blue ; soluble in water. Cluloantlilte.

d. Colour, blue or green ; insoluble in water.

AZUrite, wbick is blue, and malachite, green, are fusible, and their powder is soluble in acids with eServeacence.

libethenlte, Atacamlte, and Arsenlate of Copper are green, toaible, and soluble in acids without effervescence. Atacamite colours the Same, near the aiibitAnce, blae, and arseniates of copper emit smell oC garlic before the blowpipe.

ChrysOCOlla and Dioptase are green, and infusible.

Clwieopynte, or copper pyrites, ia only to be compared with iron pyrites, which it somewhat closely resembles. It will not be mistaken for gold, although it has the caloar of that metal ; nor for stannine, purple copper ore, or variegated copper. Stannine, although sometimes yellowish, has a greenish hue, and copper pyrites is distinguished frtun iron pyrites by being easily cut by a knife, and crushed to powder with a hammer ; while iron pyrites is much harder, scratches glass easily, and strikes fire with steel. Iron pyrites, in consequence of surface decomposition, sometimes exhibits the variegated colours of the so-called peacock ore, and is likely to be mistaken for it in this state if not tested with the knife. It is always advisable to examine the colour in a freshly-broken specimen, when the yellow colour of copper pyrites is characteristic.

Qrey copper, including UnwnUite and enargite (which are only varieties) are not so easy to distinguish, their steel grey colour being similar to that of many other minerals.

When crystallised they sometimes resemble sinoblende, but this last mineral gives a white dust when scratched, and is infusible. More complicated crystals are liable to be confounded, at first glance, with hematite or specular iron, arsenical cobalt, and grey cobalt, both of which latter contain arsenic, and with silver glance or argentite.

When massive, the analogies with other minerals are still more numerous. Grey copper and its varieties may be mistaken for magnetic iron, chrome iron, mispickel, geradorffite, stibnite, the cobalt ores mentioned above, argentite, or redruth ite.

The iron and chrome ores are much harder than grey copper, and are moreover infusible. The nickel and cobalt ores are very heavy, which is sufficient to distinguish them ; besides which, they will he recognised by means of the borax bead. Mispickel is silver white, and when struck with a hammer smells of garlic; while the light-coloured varieties of grey copper, which might be mistaken for it, do not contain arsenic. Stibnite is fusible when brought near the flame of a candle, and volatile when heated before the blowpipe. Sulphides of copper and argentite are sectile and malleable, while grey copper is brittle i besides which, the sulphides smell of sulphur when heated before the blowpipe, while grey copper gives white fumes due to antimony.

BournoniU, when massive, is also likely to be mistaken for grey copper, and a reduction on charcoal with soda will be necessary to distinguish them, when a bead of lead and copper vill be obtained from bournonite. When the prismatic crystals .

of bonmonite are longitudinally striated, they resemble stibnite and the prismatic manganese oxides, but the monganeBe orea are infusible, and atibnite volatilises entirely before the blowpipe. A ready test for bournonite is its fracture, which is perfectly conchoid al and shining.

The ores of copper, which do not possess a metallic Instre, will be easily distinguished from other minerals of similar appearance by the following characters r —

Cuprite, when crystallised, might be mistaken for ziocblende or other ntineralB of the same form, such as magnetite. It will, however, be readily distinguished by its red streak. Whan lamellar it might be mistaken for red silver ; but this mineral gives abundant antimony fumes before the blowpipe. Cinnabar, which is also red, will entirely volatilise before the blowpipe ; besides which, the difference in specific gravity is appreciable, that of cinnabar being 8, and of cuprite 6. Coprite will also give the green flame due to copper.

Black Oxide of Copper will be distinguished from black earthy manganese and cobalt wad by the borax bead in the oxidising flame, which is violet with manganese, and deep blue when cobalt is present ; while copper alone gives a bead which is green when hot, and pale blue or greenish-blue when cold.

Azurite will be distinguished from lapis lazuli and vivianite, when earthy, by being soluble in acids with efFervescenca When crystallised, aaurits does not resemble any other mineral.

Maioichiu will also be distinguished from other green minerals, which are numerous, by being soluble with effervescence in acids. The minerals likely to be mistaken for malachite are some atseniates and phosphates of copper and atacamite amongst the copper ores and, amongst other minerals, pyromorphite and copper uranite. These minerals are all green, hut of different

FyromorphiU will be readily distinguished from copper ores by its high specific gravity ; besides which it is not always green, hut often yellowish -green, yellow, or brown. Copper uranite, which crystallises in laminse, exhibits on the larger faces a pearly lustre, and fuses before the blowpipe to a blackish mass. The arseniatea and phosphates of copper are soluble in ammonia, and the arseniates give before the blowpipe the characteristic smell of garlic. Atacamite gives the bine dame characteristic of chloride of copper when brought near the flame of a candle, it not being necessary to previously moisten the mineral with acid.

Copper Ore Deposits. — Copper occurs in various kinds of

rock in lodes of very different age. It ia, of course, difficult to determine the age of a lode which occurs in crjBtalliite Bchiats or sedimentary strata, unless they are overlain by beds which are not traversed by the lode and of which the age is known ; but some copper deposita have been formed in very recent times. Where copper ore occurs ia beds or impregnations it does not follow that the ore haa in all cases been deposited at the same time as the bed in which it is found. In (rermany, however, near M&nsfeld, there is a typical instance which leaves little doubt that the ore was formed at the time of deposition of the strata or during the Permian period, the formation being known as the " copper slate." The average composition of the ore is constant over a large area, and the rock contains from 3 to 3 per cent, of copper with a small proportion of silver and gold which make it payable to work with cheap labour and fuel.

Oopper ores occur in true fissure lodes, in crystalline schists and in rocks of all ages, and are also common in eruptive rocks, especially porphyry, melaphyre, and serpentine ; and in sedimentary strata from the Cambrian period to Tertiary times.

Copper very frequently occurs in contact deposits ; where this is the case it has been segregated from the eruptive rocks or brought by hydrothermal waters which followed the course of the dykea, and lies either at or near the junction of one of these rocks with sedimentary strata or at or near the junction of two eruptive rocks of different ages. A well-known instance of a copper-bearing contact deposit is that of Monte Catini, in Tuscany, where the rock which carries the copper is serpentine. The ore in deposits of this sort occurs in rounded irregular masses, and the features of the lodes are of a very variable character.

It should be borne in mind, especially when exploring a new country, tliat copper is frequently associated with rocks of a dark colour, which are very often green ; but it must not be supposed that the colour is imparted by copper, for it is generally due either to some other metal, such as iron, or to the presence of a green non-metallic mineral, such bs chlorite.

Serpentines and hornblendic rocks are often associated with copper ores, but green serpentines owe their colour to iron, nickel, or chromium; and if copper is found disseminated through some of them, it is the exception, and not the rule, unlesa in the immediate vicinity of ore deposits. On the contrary, iron and chromium are found in all serpentines, and nickel frequently occurs.

Hornblendic rocks are green, grey, or black, according aa

170 PEtOSFKCTlMO FOB MINBRAL3.

ftctinolite (which is green) or common hornblende (which is black) occur in them, Actinolite is of frequent occurrence in some Bchiats, and black hornblende in dioriles, and other dark coloured rocks which are associated with copper ores.

Other green minerals enter into the compoaitiou of some rocks, especially gabbros, so it may be clearly understood that the green colour of rocks is seldom due to the presence of copper; and although green rocks are frequently associated with copper ores, they are not always to be looked on as indications of the occurrence of deposits of this metal.

Near Wallaroo, the most reputed mines of South Australia, hornblende is of frequent occnrrenoe in the rocks of the country, which are mica and talc schists, the nearest ridge being composed of syenite.

In New Caledonia the copper region oocnpiea both flanks of a mica schist range in which hornblende is very common, and occurs associated with garnets, chlorite, and white and green micas ; and through these rocks serpentine protrudes at places, especially in the vicinity of the copper deposits. The main deposit which has been worked consisted of several parallel shoots or pipes of ore enveloped in foldings of the schists.

Serpentine occurs in several parts of Australia where copper also is known, and also in New Zealand ; but, although serpentine is frequently associated with metals, and especiuly copper, it does not follow that it is always accompanied by such deposits; in fact the serpentines of the in Conrwall, although in a copper-bearing district, are devoid of copper ores themselves; besides which, although contact deposits are generally numerous where they occur, they are seldom of great and are very irregular.

Australia is wonderfully rich in copper. It is sufGcient to mention Wallaroo in South Australia, Peak Downs and Cloncurry in Queensland, Cobar and Nymagee in New South Wales, and Mount Lyell in Tasmania.

Copper ores generally occur with quartz as a gangue ; but occasionally some other minerals, such as fluorspar, barytes, and calcite, are found in association with them.

The ores of copper, or indeed of any metal, are always associated with other ores in greater or less quantities; but those veins in which there is the least variety are generally the most valuable, since they are more easily concentrated, and their metallurgical treatment is more simple.

Copper ores, especially copper pyrites, gtey copper, and melaconite occasionally contain silver and gold. At Lake Superior

Tin. 171

native copper often containa nuclei of pure silver enclosed in the mass of copper without being alioyed with it.

Iron pyrites sometimea contains copper at the rate of a few nnits per cent., as in Cornwall and at Huelva in Spain, where some extensive deposits of pyrites are worked for sulphuric acid and yield 1 or 2 per cent, of copper, with a very amall proportion of silver and gold, but still sufficient to give a reasonable profit. Poor copper ores or cupriferous tailings, when in sufficient quantities and when suitable materials are at hand, can lie worked very cheaply by one of the many wet processes known, and particles of the sulphides of copper when BO finely disseminated through a matrix as to render any system of water concentration inapplicable, can be collected by the Elmore process of oil concentration.

Yellow copper ore is seldom pure copper pyrites, but is generally nixed with more or less iron pyrites ; so that an assay is always necessary to determine the value of an ore. It is often the case that a picked specimen of apparently pure chalcopyrite mixed with a small quantity of quartz will yield about 25 per cent, of copper, or even less, instead of over 33 per cent., which it should do theoretically. This low return is not due to the presence of quartz alone, but to an admixture of iron pyrites ; and it is seldom the case that a ooncentrated pyritous ore yields more than 15 per cent, of copper on an average in a large consignment.

CHAPTER XIV. Tin — Titanium — Tungsten — Molybdenum.

Tin. Casaiterlte or oxide of tin is the only ore of this metal, although another mineral, Stannine, containing tin, copper, and sulphur is known. Stannine is not sufficiently abundant, however, to be of much importance, and, although it has been found in lodes of some size in Comwidl, it is sold aa an ore of copper and not of

Tinstone stands nearly by itself in its mode of occurrence and formation, as a type of a strongly marked class of deposits. It is always associated with granitic rocks, quarta -porphyries, or gneiss, all of which are of analogous composition, being rich in silica, which orystalliaes as quartz, and being called in consequence "acidic" rocks. Tin lodes are nearly all of great antiquity and

172 Frosfegtiito Fob Misebals.

occur only in those of the above-named rocks which are charaoterieed by the presence of white mica. It is only in two or three places in the world, notably Tuscany and Elba, that granites of this type have been erupted during recent times, and they contain tin in small quantity, as well as some of the minerals usually associated witn it, such as tourmaline, lithia mica, and emerud.

Although this fact is of no immediate practical value, it is important, because it shows that there really are laws which govern the distribution of minerals, although these are sometimes Tery obscure ; but by constant observation it is certain that, amongst discoveries of merely Boientific interest, laws capable of practical application will occasionally be found.

Tinstone is always associated with quartz and rarely occurs in green rocks, unless their colour be due to chlorite ; nor in dark coloured rocks, except where stained red by the decomposition of ferruginous minerals ; neither is it found in limestone.

Those granites which are characterised by abundance of white mica have, with good reason, been termed "tin granites," and a coarse-grained rock composed of granular quartz mixed with white mica, and called "greisen," occurs in all the tin fields of the world — e.g., Cornwall, Germany, and Australia.

The minerals most commonly associated with tin — viz., topaz, mica, tourmaline, fluorapar, apatite, and other rarer minerals containing fluorine — seem to show that it was originally contained in the granite as fluoride of tin, and that the associated minerals have been formed at its expense. It is an established iact in the genesis of minerals that fluorine is always accompanied by silicon and boron ; it is therefore natural to And silicates containing boric acid, such as tourmaline and axinite, in association, with tin. Other minerals which frequently accompany this metal are wolfram, molybdenite, mispickel, garnet, beryl, &o.

Tin appears to have been brought to the surface disseminated through the granite in which it occurs; and has subsequently been concentrated in all the cracks and joints of the rock, forming in many cases a perfect network of veins known aa stockworka; the best known instance of this class of deposit being in the Eragebirge Range in Saxony. At Zinnwald, the tinstone is concentrated in a number of curious concentric zones, which, for a thickness of about I foot, are impregnated with tin, BO that the whole of the rook has to be removed for the extraction of the ore. The rocks constituting these zones are greisen impregnated with tinstone and wolfram, and they have been

Tin. 173

frequently displaced by vertical and inclined fissares which reach the surface.

The tinstone in these beds appears to have been formed contcmporaneoQsly with the greiaen in which it occurs, and the greifien itself is probably a granite altered in sxiti, topaz being formed at the expense of alumiaona silicates.

The stockwork at Oeyer consists of a mass of granite in mica schists, traversed by numerous tin lodes, from which the ores and other minerals have penetrated into the joints of the granite. The same veins extend into the surrounding mica schist, but there they appear to contain less ore. Considerable confusion exists in the use of the term "stockwork," and so the foregoing instances are given in illustration of this class of deposit, bub in the chapter on " Irregular Deposits " the different characters have alresidy been described.

The Altenberg deposit consists of a rock called "stockwork porphyry," or "zwitter rock," and is tin-bearing throughout; but the ore is so finely disseminated as to be hardly perceptible, and in such small quantities that often one-thiid to one-half per cent, only can be produced from it. The rock is a finegrained greisen, and the term of porphyry is very inappropriate. It meies gradually into the surrounding country, which is composed of granite, chloritic granite, porphyry, and quartz porphyry, no clear line of demarcation existing. The rock is dark coloured, sometimes almost black, and consists of quartz, mica, chlorite, tinstone, &o., and pyrites is disseminated through it in minute particles ; but the quartz alone can be distinctly recognised; it frequently occurs as grains without crystalline structure. Molybdenite, bismuth glance, copper pyrites, iron pyrites fluorspar, topaz, itc., also occur, and the rook is traversed by numerous quartz veins.

Tin ore often occurs disseminated through a rock in which the boundaries of the stanniferous deposit are not well marked, and two classes of these deposits may be distinguished.

1st. Disseminations or impregnations formed at the same timeas the rocks in which they occur.

2nd. Impregnations in which the ore has been introduced by the mineral waters, which charged the lodes, traversing the rocks.

This last class of impregnations is well illustrated by the stanniferous capels which adjoin many tin-beariog lodes, and are very variable as regards their width. Tin floors are also illustrations of their disposition.

The ore ia found in places as crystals and crystalline patches ;

174 PROBPECTIIta FOB MINERALS.

in others, the particles are bo finely divided as to be invisible to the naked eye ; and in others, again, it occurs as minute fipberical aggregations.

Tinstone also occurs largely in lodes, and these are generally the oldest lodes of the district ; but in some cases in Cornwall copper lodes have been known to change to tin in depth, bo that this law cannot be looked upon as infallible.

Tests for Oaasiterite. — Cassiterite or tinstone is a mineral which should be very readily recognised, and yet there is probably no other ore for which so many different minerals are mistaken. Its specific gravity alone, between 6'8 and 7*1 should be sufficient to distinguish it from the greater number of minerals which resemble it more or less closely.

Jiutile most closely resembles tinstone in crystalline form and external appearance, but it is much lighter; specific gravity, 42. The streak or powder of rutiie is brown-yellow, while that of tinstone is from light grey to brown.

Wolfram has nearly the same specific gravity as tinstone, and so will be associated with it in the tin dish, but the streak of wolfram is black or reddish-black, and the hardness about that of glass, while tinstone is much harder.

Zinchlende, commonly called " black jack," is not heavier than Tutile, specific gravity 4'3, and is not so hard ae either rutiie or tinstone, being scratched by a knife. Its streak is yellowishwhite to brown, approaching that of rutiie, and its lustre and external appearance are much like tinstone. When it contains much iron and is black, and especially when found in alluvial beds, it resembles tinstone, but will be easily separated from it in the tin dish, or recognised by blowpipe tests.

Many other minerals are at times mistaken for tinstone, but they can be very readily distinguished.

Chromite has about the hardness of glass or wolfram, but is not BO heavy as that mineral. In the tin dish it would be found with rutiie, ifec, its specific gravity being 4-5 ; so that it would be readily separated from tinstone. It also affords a green bead with borax. Magnetite, titanic iron, and specular iron have all about the same specific gravity, and will, as well as chromite, yield a magnetic bead when heated on charcoal with soda; magnetite and titanic iron are themselves magnetic.

The genu which are sometimes taken for tinstone are all harder than orthoclase, and, with the exception of guuet, will not be scratched by tinstone itself. The lightest of these are spinel, specific gravity 3'5, and tourmaline, specific gravity 3-2 ; and it is only the black varieties which are liable to be mistaken

Tis. 176

for tinstone. Tonrmaline which crystallises in prisma ; and garnet in rhombic dodecahedrons, are both fusible before the blowpipe ; but, apart from negative tests of this sort, tinstone tnaj be readily reduced on charcoal, with cyanide of potassium, to a metallic state. The tin tns obtained will not give any white or coloured coating on charcoal like zinc, lead, antimony, or bismuth ; and when the fused mass and charcoal are scraped off, crushed in an agate oiortar, and washed, the tin will be separated in metallic scales.

The mode of occurrence of the different minerals will also afford some guide as to their characters, except of course when they are found in alluvial deposits.

Casaiterite Deposits. — Tinstone, as already mentioned, is essentially a mineral of the acidic eruptive rocks, such aa granite, quartz-porphyry, and greisen; but it also occurs in lodes traversing crystcdline schists, such as gneiss, mica schist, or chlorite schist, and also in clay.a!ate, or " killas," but never at a greater distance than 3 miles from granite.

Wolfram also occurs in lodes, as at the East Pool mine, near ; but rutile, zircon, garnet, and tourmaline mostly occur either disseminated through the rocks or crystallised in cavities. Wolfram and tourmaline are generally found in tin bearing rocks, but spinel (pleonaste), chromite, and titanic iron are generally associated with basic rocks of dark colour, such as serpentine, basalts, Ac, and are, therefore, less likely to he mistaken for tinstone. Magnetite occurs in considerable masses in crystalline schists, horoDlende schists, and serpentines ; and is also disseminated as grains through many eruptive rocks, such as basalt ; but it is chiefly associated with chlorite.

Hematite is found in rocks of all ages and of every description. Lastly, zincblende occurs in lodes, especially with quartz containing galena, gold, &c.

In alluvial deposits tin occurs, under the same conditions as gold, in river beds of various age, which are sometimes covered by flows of basalt. Some leads are worked under the basalt in the northern part of New South Wales, and are known as ''deep leads" as well as the similar auriferous deposits; but those which can be easily drained are rapidly becoming exhausted, and the more heavily watered leads will require to be worked on a more extensive scale to be profitable.

Rolled tin ore la in some places found in boulders of considerable size, from 5 to 20 and even 36 pounds in weight; for instance, in the Butchart tin mine. This mode of occurrence is similar to that of the tin in the Straits Settlements, and

ehowB that aome of the lodes muat contain pockets of ore of Urge aizB.

When stream tin ore is derived from concretionary lodes, ach as occur in Gomwall and elsewhere, it assumes a radiating; fibrous appearance which makes it resemble wood, in consequence of which it is called " wood tin." Occasionally the fragment preserves the impression of a crystal of quartz on which it haa been formed. When the concretionary structure is marked only by small mammillated tubercles, it is termed " toad's eye tin " or "shot hol'd tin."

When stream tin is coarse, it often preserves its orystaUine structure, eaid crystals as much aa an inch in length, in which the edges only are rounded, are not very rare.

In alluvial deposits, it may be remarked, tin ore has generally been separated irom its associated sulphides and arsenides. Wolfram has, in the past, been the most objectionable of the impurities which are mixed with tin, as its high specific gravity renders the sepai'ation by dressing moat difficult, magnetic separators have, however, completely overcome this difficulty.

Tinstone assumes many different colours and shades-.7., ash-grey, light brown, pink, ruby-red, amber-yellow, dark brown, and blat. Its streak, therefore, varies irom white to grey.

Chemically pure stannic acid being white, those specimens which are lightest in shade will be the purest. Some specimens from the Giant's Den, Kew South Wales, are pure white.

Very dark-coloured varieties generally owe their black shade to manganese or iron, which can often be detected by the blowpipe ; and, more rarely, tantalic acid is present, also giving a dark colour to the ore.

The Mount Biachoff deposit of tinstone in Tasmania occurs under circumstances which are quite exceptional.

Mount BiechoQ* rises nearly 3,000 feet above sea-level. Within 160 feet from the summit there is a crateriform depression of several acres in extent, the sides and bottom of which have been composed of a rich tin-hearing detritus resting on a bottom of slate. The depth of the deposit was about 30 feet, and the rich detritus was composed of the elements of the rock itself, a kind of enritic porphyry which has decomposed in litA. Tin ore lodes have been found high up the mountain side.

Titanium occurs in nature in the form of titanic oxide ; but there are three minerals which have this composition, although they vary in their crystalline form.

Tin. 177

Bntile reBembles tin ore in appearance, and occurs, Bometimes, tmder similar geological condition ; but the crystals of rutile are more needle shaped or columnar, anil they otlea penetrate crystals of quartz or felspar. In quartz reefs rutile often accompanies gold, and is sometimea associated with chlorite, as also is tin ore. It is used for preparing acme enamels.

Octahedrite occurs in elongated octahedrons, sometimes so splendent as to be mistaken for diamonds ; and

Brookite is found in reddish-white plates with striated surfaces, and of a bright red colour by transmitted light.

The mode of occurrence of these two minerals is frequently the same as that of rutile, and they also sometimes accompany gold. Their lustre is adamantine, and they are likely to attract the eye when found in alluTial deposits, in which they are frequently associated with the diamond.

Titanic acid is employed for making a yellow colour used in painting porcelain, and also for giving the requisite tint to artificial teeth.

Hidenl.

par

Hud-

Hpeclflc Omity.

Cuiitenle, . Stannlne, .

Sq,0 3, So, Cn

Sd25 Cd29

Sqosre prUms,

twins. Geaerally mas-

Ti,0 Do.

Light.

brown Grey

plate. Aaamantine,

emi-metaUia,

black.

Brookite, . Wolfram, .

Do. WO.Fe.

W,0, Ca

White

Brownred, or blackish brown

White

Molybdenite,

Mo,S

Ludlike

Marks paper

like plnmU-

mi flexible. Generally earthy; buIyellow.

Mo,0

Its Prosfectinq For Hineralb.

Wolfram, which is the tungstftte of iron and maDgaaese, often accompanies tin, native biemuth, and topaz, as already stated. Its specific gravity is nearly the same as tinstone, and it is in consequence very troublesome to the tin miner. Its colour is black, and it is generally found in crystals -with large cleavages, or in laminie with & semi-metallic lustre. The thin laminn are opaque.

Woliram is used in the preparation of some colours and enamels, and enters into the composition of some special kinds of steel ; besides which tungstate of soda, which ia used as a mordant and for fireproofing fabrics, ia prepared from it.

Tungsten may also be used as a substitute for tin in the manufacture of purple of Cassius.

Scheelite, which is a tungstate of lime, occurs in irregular masses in a quirtz lode traversing crystalline schists near the bead of Lake Wakatipu in New Zealand, and also near Armadale in New South Wales. It is white, and very heavy for a white mineral, having a specific gravity of 5*9 to 6'I. It forms a blue bead with microcosmic salt in the reducing fiame.

Molybdenuu.

Ifolybdenite, or sulphide of molybdenum, occurs in New South Wales in quartz reefs containing tin and bismuth, and worked for the latter metal ; it is also frequently met with as fiakes and crystals in crystalline metamorphic rooks. Id Oalifornia and Sweden it occurs in considerable quantities in this disseminated state, and were the demand constant a fairly large supply could doubtless be secured. It is usually accompanied by an earthy yellow coating of molybdic oxide, called molybdite.

Molybdenite is used for the preparation of blue carmine for colouring poroelain, and also for the manufacture of molybdenum steeL

These minerals, wolfram and molybdenite, have been described here because they are frequently associated with tinstone in its natural repositories.

n,g,t,7.cbyGOOglC

Chapter Xt.

Zinc— Iron— Nickel — Cobalt— Uanganese — Cbromiiua — Uraniam.

Zinc.

Testa, — It has been stated in the chapter on the use of the blowpipe that alumina moistened with titrate of cobalt becomes blue when heated ; and that under the same circumBtauces oxide of zino becomes green. The ores of zinc should be distinguished by this test ; but some of them do oot give a olear green, but only a bluiah-green colour ; besides which some other oxides are also coloured green by this treatment. The best way, therefore, to ascertain the presence of zino, is to treat the mineral on charcoal with soda, so as to reduce the zinc, which, immediately it is reduced, volatilises, and is again oxidised, forming a coating on the charcoaL This coating being heated, will assume a sulphur-yellow colour, and become white again when cool ; the test, with nitrate of cobalt, can then be made on the oxide, and a green colour obtained.

When oxide of zinc is moistened with a drop of solution of sheUac in spirit, it assumes a marked pink colour without being heated, whilst alumina, under the same circumstances, is a faint yellow with a shade of red. This tast should be tried with the two substances in order to note the different shades of colour.

Among the zinc ores recorded in the table, the carbonates and silicates only are at all difScnlt to distinguish from each other.

The sulphide of zino or zinoblende, commonly called "black jack," is easily recognised if treated with hot hydrochloric acid, as it gives a smell of rotten eggs (sulphuretted hydrogen); and the same result can be obtained without heating if a small quantity of pure iron filings is added to the acid. With soda on charcoal before the blowpipe ziocblende gives a hepar which, with water on a silver coin, tarnishes or blackens it. The red oxide zincite is conspicuous by its colour, and is very rare.

Probpectino Fob Minerals.

The carbonates and Bilicatea are nil white, or tinged with brown, and will bo idsntilied as followB : —

SOBATOBED BT CaLOITE, AND VERT EASILY BT A KnIFE — AmOF-

phouB — Hydrous — Efferreaces with Acid. Zlno Bloom. 80BATCH8B Oaloite and EVEN Fluob Spar — Nor Sobatched

TEBY EASILY BY A KviFE.

1. Efferyesces with acid. Calamine (Smithsonite of Sana).

2. Does not efiorveace ; ooncretionary or crystallised.

a. Heated in a tube gives off water. Oalmei or Eleotrio Calamine (Calamine of Dana).

b. Does not give off water when heated. Villemite.

Table Of Zinc Oebs.

Per.

?s-

Calamine, .

B2

Small orystalB or

Zino bloom, .

Hydrous carbonate

Shining

H

Small cryatalB.

Oahnei. .

S4

Eleetric and phosphorescent when bMttid—

Oxide

Ho

Otangeyellow

Sulphide

H-4

White to

reddishbrown

Btalli.ed or

Zlno Ores. — Zincite occurs in Kew Jersey, U.S.A., associated with a mineral called " franklinite," which is an oxide of iron, manganese, and zinc. The two minerals are treated as an OM of iron, the zinc being deposited at the mouth of the blast farnace as oxide, and not interfering with the production of iron.

Zincblende occurs in rocks of all es, and accompanies ores of load, copper, tin, silver, and gold in lodes ; but it is only when a large percentage of blende is present that the ore is worth treating for idno. In the mines where it occurs with galena, it

Iron. 181

sometimes forms half of the metallic ore, and can be separated from lead and some copper ores mechomcally, its specific gravity being very low. Deposits in which zincblende occurs by itse are so rare that an instance deserves to be mentioned. In Sweden a remarkable deposit of blende occnra in gneiss forming a belt 200 fathoms in thickness, which can be followed for a distance of nearly two niilea along its strike. The enclosed deposit of zinc ore has a very varying thickness, dips at angles from 70" to 80°, and consists of a number of lenticular masses, which sometimes attain a thickness of over 12 &tbomB. The blende, which is black to yellowish in colour, is occasionally accompanied by argentiferous galena, but more frequently by iron pyrites and magnetic pyrites. The other minerals found are amazon stone, hornblende, talc, chlorite, garnet, black tourmaline, and bitumen ; calc spar is rare. i

Blende is frequently found with silver and gold, and is sometimes suffidently rich in silver to be treated for that metal, as in Portugal and, again, in New South Wales at Broken Hill.

Those ores in which zinc occurs as carbonate or silicate are found in peculiar deposits in limestone, and are frequently connected with veins of zincblende. The mineral eolations which, in suoh rocks as slate, have deposited blende or sulphide of zinc ; when in contact with limestone, have decomposed that rock and formed cavities, in which calamine has been deposited together with the other carbonate and silicates mentioned in the table.

The appended sketch, which represents a section of the celebrated deposit of Moresnet, near Aix la

JTuchs, lUustratea the BmtonB; 3, quartz and dolomite; mode of occurrence of tchiats and grauwocka ; S, calamine; these oxidised ores, which C lincbieadB vein, have been, and are being, worked in preference to the sulphides which occur in depth. The carbonates and silicates are all oxidised suriace ores of zinc, as carbonates and silicates of copper are surface ores of copper.

Iron,

This group includes some minerals which, in consequence -of their abundance, are of great value as ores of iron j and others

luuile

which, being rare, of no conunerci&l r&loe. Those of imporUnce as iron orea are hnmatite, goethite, limonite, magnetic iron, and siderite.

They wilt be easily recognised bj the following charaoteristica: — HBtnatite, either pore and MTBtnUiaed, or impore and earthy, gives a red doit when scratched, and ii anbydrons. Ooetliite and limonite both contain water, and give a brown dost or slovak. Magnetite will be roctnised by bring attracted by a magnet, and even sometimes, in a compact mass, acting as a magnet itself. Stderite, being a carbonate, will efierreece with add when heated, and resembles calc spar, but ia light brown instead of white.

Hteoiatite ooonrs in lodes, but then are not the most import tant depoiits known. In the description of stratified and irregular depoeita, examples have been given of the occorrentM of ese ores in beds or lenticular mMues in sbatified rocks. They also occur largely as metasomatio replsoements of calcareous rocks, as in Cumberland and Bilbao. As a rule, hiematit is aaaociated with quartz.

As deposits of only scientifio interest, haematite is to be found in the Brazilian sandstone called itaoolumite and in itabirite where it ia accompanied by the octahedral variety of hsmatite, martite," and where diamonds are also found. It also occasioDfilly occurs in crystalline rocks, as in granites, and has been found in some volcanic rocks of Tertiary age, as in the crater of Vesuvius.

Bven when occurring as a valuable ore of iron, red luematite is rarely so pure as the Cumberland and Lake Superior ores, but is generally mixed with earthy matters, forming beds of great extent. Bed ochre is a soft, earthy luematite containing fine clay, and is used in the manufacture of paints.

OoetMte and limonite, or brown hwmatite, can be considered together, the difference between them being only in the percentage of water they contain. Goethite is very rarely crystallised in definite forms, but generally occnra in fibrous concretionary or granular masses. It contains about 10 per cent, of water. Limonite is never crystallised in definite crystals, but is sometimeB found in fibrous concretionary and often earthy masses, and also mixed with sand or clay. It contains from 8*2 to 10 per cent, of water.

It occurs in the upper parts of decomposed pyrites or copper lodes, where it forms the " gossan," ana it ia also interesting to note that some of these gossans have been worked for iron ore on the snrfaoe and have changed into copper deposits

in depth. Where limonite occurs as & reaalt of the decomposition of pyrites it must be expected to contain sulphur, which will interfere in its metallurgical treatment as an ore of iron.

Extensive stratified deposits of these oros occur in Europe, there they are known as oolitic iron ores. Their percentage of metallic iron is low, from 26 to 30 per cent., but they form beds sometimes over 40 feet in thickness and covering an area of over SO miles in extent.

The so-called "bog iron ores" which are sometimes very rich belong to this group, as also do the " pisolitic ores " which occur in pebble-shaped concretions about the size of a pea.

Mnetite exists in lodes, beds, and segregations, sod also as impregnations in crystalline schists, generally associated with such minerals as chlorite, hornblende, and garnet which are rich in iron, as well as with quartz. Some of these deposits are similar in character to the hematite deposits of Cumberland.

In some places magnetite occurs in very extensive deposits sufficient to affect the working of the magnetic needle at a considerable distance. The ore when pure contains 72 per cent, of meta), and is the richest ore of iron ; but impure magnetites also exist in which the contents of metal is as low as 40 per

Biderite, or spathic iron, occurs in lodes, beds, and segregations. This ore is nearly always mixed with the isomorpbous carbonate of manganese, diallogite, which increases its value for the manufacture of steel. Siderite in lodes often contains sulphides, which necessitates roasting the ore before smelting; but when decomposed at the surface it affords a valuable ore composed of an earthy mixture of iron and manganese oxides free from sulphur.

Another variety of siderite occurs in lenticular concretions or disconnected beds, in the coal measures of Europe; and, in consequence of its concretionary or banded structure, it is called sphero-siderite or clay band; and a variety mixed with carbonaceous matter is known as ''black band ironstone." This ore often contains phosphorus.

Titanic Iron is mostly found as eand formed by the degradation of rocks of eruptive origin, which contain it as grains or small crystals, and in that form it exists as extensive deposits on the west coast of New Zealand at Taranaki and elswhere. Titanic iron crystallises in the same form as htematite, and consequently occurs in mixtures of no definite composition. It baa already

PBOSFICTUrG rOB HINK&ALS.

beea alluded to in the chapter on tin, u forming put of the socalled " blacic tand," so often met with in aUnvial depoaita. Titanic iron ia also found in reina or beds in dioiite, as in Norway, where orystala occur weighing aa moch aa 16 lbs. It cannot be oonaidered as a volaable ore of iron, as the preaence of titanic acid makea it very difficalt to melt, although a small quantity ia aud to improTe the quality of steel.

Vivianite, a phosphate of iron, is a mineral of a deep blue or green colour. It is found with iron, copper, tin ores, &o., and ia often cryatalliaed in old bone which have been buried and partially decompoaed in ferruginooB soil ; and alao in beda of clay.

Sulphate of Iron, a soluble aalt, occurs as a greenish efflpreacence from the decomposition of iron pyrites. With tincture of galls it gives a black colour and is Uie basis of common ink.

Table Ov Native And Oxidised Iron Ores.

Hatal

Native Iron, .

Nearly pare

Bare-in some

Elrtra-terroatrial

Meteoric iron,

Alloved

with niokel.

Ni4

loie

origin.

to.

6i-6*

Black

Strongly magnetic.

Titanic iron, .

Iron and

Vari-

BlMk or

Often oocnn aa

titaninm

able

brown

Mnd; slightly

oxidea

magnetio. KhoLribohedric

Hsmstite, .

Cherry-oxide

red

Goethite,

Hjdrona oxide

6-fil

Ochre-

Often fibroin or

Limouite, .

Do.

Do.

Aa aboTe or

earthy. Cryatalliaed,

Vari-

Light-able

lenticular, to.

Virianita, .

lJ-2

Soluble, green-

Solpbate of

Stdphate

from decompoiition

of pyrites.

Iron. 186

It must be remembered the percentage given in the third column are those of pure, or nearly pure, mineralB, and that ordinary ores will be poorer because of the impurities contained in them; this observation a])plieB equally well to all the similar tables.

Iron Pyrites. — All the minerals under this head give a magnetic mass when heated on charcoal before the blowpipe. Every prospector knows the common yellow pyrites to which he refers as "mundio" and not one will mistake it for gold, although some ipecimeus have a beautiiul golden colour. The most ready test is its hardness, which enables pyrites to strike fire with steel, giving at the same time a smell of sulphnr.

There are two species of iron pyrites of the same composition, but cryBtallising differently. "Pyrite" is the mineralogical name of the species which crystallises in cubes and modifications of the cube ; the name " marcaaite " being reserved for the other species which, being of a paler yellow, is often called "white pyrites," hut most not be confounded with mispickel, known amongst miners as "white mundic." Morcaeite crystallises in prisms, which often aiTect the form of tables.

Both pyrite and marcasite ore found in concretions, stalactites, and radiated balls. Their hardness is the same, bat the specific gravity of marcasite is less than that of pyrite. They are both readily decomposed, especially when exposed alternately to the sun and rain; this property is sometimes taken advantage of in liziviation processes for the recovery of gold or preparation of sulphat of iron. Marcasite, however, decomposes with greater facility than pyrite. It lb often found replacing the carbonate of lime in fossil shells, and these are difBcnlt to preserve onleas covered by a substance which prevents access of air. It is to the decomposition of marcasite and pyrites, and the heat generated during the process that many of the fires in coal mines and on board ship, said to originate from spontaneous combustion, are due.

There is another kind of pyrites which is not of such common occurrence — viz., magnetic pyrites or pyrrhotine. It contains more iron than the common pyrites and is slightly magnetic in its natural state ; its colour is so different, being bronze-yellow.

Uiapickel, commonly called "white mundic," differs in composition from the other forms of pjnjitea by the substitution of arsenic for part of the sulphur ; its tin-white colour makes it an easy matter to recognise it. Its hardness is not so great as that of ordinary iron pyrites, but it also strikes fire with steel, and then gives a smell of garlic, due to arsenic. It

wUi be easily diatinguished from arsenical cobalt smaltine) and grey nickel (geredorffite), which it reaemblea, hy the borax assay before the reducing flame of the blowpipe. With smaltine the bead will be blae, and with geradorffite light green, when cold, if cobalt is absent ; while the borax bead, with mispickel, would give the reaction of iron — tIe., bottle green when cold. The bead of nickel and the bead of iron Yill be best distingnished in the oxidising flame ; when cold, the nickel bead is red, while that of iron u light yellow or colourless.

Common iron pyrites occurs as an accessory mineral in all metalliferons veins. It always accompanies gold in the ree when this precious metal is free ; and is generally auriferous itself to a greater or less extent, being seldom ftee from traces of gold even when free gold does not occur in the district.

From an industrial point of view pyrites should he considered as an ore of sulphur, being used in the manufacture of sulphnrio acid, the sulphates, and sometimes sulphur itself.

In sedimentary rocks pyrites is frequent, especially in foasiliferous beds, having been deposited in them by the decomposition of organic matter. As a rule, marcasite is the variety found in sedimentary formations which have not been metamorphosed, while pyrites occurs in lodes and metamorphic rocks.

It has been said that pyrites is easily decomposed in Nature. This decomposition takes place in two different ways. In the first, a soluble sulphate of iron is formed with the generation of heat ; this explains in some cases the high temperature of mines and mineral springs. In the second, the sulphur is slowly displaced and hydrous oxide of iron formed ; this explains how it is that at the surface, or in exposed parts of a pyritous deposit, cubical crystals of limonite frequently occur, which, if broken, are found to contain a nucleus of undecomposed pyrites in the oentre.

Magnetic pyrites often contains from 3 to 10 per cent, of nickel, and is then mined for that metal. Nickeliferous pyrrbotine occurs in veins in diorite iu Italy, and in porphyry in Scotland, at the contact of gabbro with tixe country rock.

Arsenical pyrites is practically an ore of arsenic, but often contains gold or silver. It is more frequently associated with tin and copper ores.

n,g,t,7.cbyGOOglC

mOKBL AHD C

TABLE OP SULPHUfiETTED IRON ORBS.

combined with

Pt'lT.'

Hird-

8trel£.

Remark..

p.rif,

Pyrrhotinfl, . Mispickel, .

S

S.Aa

S54 S64

As 43

S&#x27;6

Grey

Greyish-

S, Salphur; As, Anemc. Nickel aud Cobalt.

The ores of nickel and cobalt are of two claBses — viz., these in which the metah are combined with arsenic, sulphur, or both ; and those in which the metals are oxidiBed.

The first cUsa includes all those ores which are mined in Europe, where they exist in veina in granite, gneisB, or Ecbista, and at the contact of these rocks with diorite, gabbro, &c. In these deposita the oxidised or surface ores are relatively rare ; but in New Caledonia they form extensive deposits in serpentine and asBociated rocks, and have been segregated from these rocks into Gssnres of more or leaa importance.

The ores of nickel and cobalt, which are mostly arsenides, generally occur together ; and, in Germany, accompany some copper and silver ores. In most of the European ores the proportion of cobalt is nearly one-tenth that of nickel, and the most common ore of nickel in Europe is nickeliferous pyrites or nioopyrite. At Tal Seaia in Italy it occurs at the junction of diorite with hornblendic gneiss.

At Eterlien in Norway the eame ore also occurs in a contact deposit between schistose quartzite and gabbro, and sometimes the gabbro itself is sufficiently impregnated to be worked to advantage. In Sweden it forms large veins in granite, and is generally accompanied by other sulphides, especially copper pyrites.

The mineral of next importance is copper nickel, or nlooolite, which occurs in Austria in veins traversing talcose and hornblendic schista, aome beds of which are impregnated with pyrites

and mispickel. The ore there also contains irhite nickel or ehloantfaite, besides copper nickel and argentiferous grey copper. Although the nickel and cobalt ores are not easy to recognise at a glauoe they will generally be detected on working the outcrops of lodes by the stains which proceed from their decomposition. These are oxidised products in the form of arseniates, and they are generally found accompanying the arsenides. The arseniate of cobalt is of a pink or peach blossom colour and is known as "erythrine" or "cobalt bloom"; and the araeoiale of nickel, called " annabergite," is apple green. That the ores of nickel frequently contain cobalt is illustrated by the &ct that both these stains often occur on the same specimens of ore.

At the present time the nickel and cobalt indnstries are rapidly increasing, since abundant deposits of those metals have oeen found and worked in New Caledonia and Canada.

The ore in Kew Caledonia is a hydrous silicate of magnesia more or less impregnated with oxide of nickel, and containing, as an arerage, 8 or 10 per cent, and sometimes even 30 per cent. of nickel in picked specimens, It occurs in veins 2 feet or 3 feeb thick and over, in a decomposed serpentine.

He best ores are sometimes mixed with rounded fragments of serpentine, forming a kind of "breccia"; but these veins have not been found to oontinne rich to great depths. The form of the best quality of ore, which is of a beautiful emerald green colour, is concretionary or stalactitic It has evidently been segregated from the enclosing serpentine which sometimes con* tains -26 per cent, or even nearly 1 per cent, of nickel Thess minerals have been named Ifoumeite and Qamierite, but they do not appear to have any very definite chemical composition, the percentage of nickel varying within somewhat wide limits.

The cob&It ore of New Caledonia is an earthy manganese oxide called Wad mixed with a small percentage of oxide of cobalt from 2 to 16 per cent. It is found in decomposed serpentinous rocks, in nodules and small veins of concretionary structure ; and sometimes also encrusting roots of trees, thus showing that the percolating liquids from which it was precipitated are still in circulation.

Blowpipe Tests for Kiokel and Cobalt. — In using the blowpipe for the determination of nickel and cobalt minerals the following notes will be of value when the two occur together, either in the same mineral species or mixed together as in some mines. The mineral should be heated on charcoal so long as arsenical Aimes escape and then fused with borax. If there is no iron present the bead will be blue ; but, if there is much iron,

Nickrl Oobalt.

it will be first bottle-green, changing to bluish-green. The bead must then be removeil from the platinum wire and heated in a fresh borax bead which will then become blue. More borax should be added as long as the bead shows an blue colour in the oxidising flame, the blue borax being broken off after each operation ; and eventually, if there is nickel in the ore, the bead will be colonred brown. If the presence of copper is suspected, it will be recognised by fusing the last borax bead with microcosmic salt ; if copper is present the glass will become green. With the information thus gained and the characters enumerated in the tables it will be easy to diatingaish the difierent minerals. TABLE OF COBALT AND NICKEL ORES.

Comhlned

Hird-

Uluanl.

Per cent.

Millerite, .

S

Ni64

In oapillary fannsyellow cryBtals.

Nickeline or

Ni

B-6i

Dp

ReddUh-grey or

oopperoickel,

brown

pale copper.

Ab

Ni28

Tin-white.

whiteniokel,

Oendorffit, .

Aa

Ni32

Silver -white or steBl-grey.

Nioopyrite, .

Ni20

Light-

Not magnetic.

Ni33,Co

Datk-grey

Steel.grey.

Cobsltine, .

S,A.

Co 35

gV

Silver -white or reddish; distinct cleavBgea.

Tin-white orated-

Smaltine, .

As

Co 28

Bl

black

grey-

S,As

Co 24

Black

Deep tin-white ;

Co 10

Sm

Greyish-

Deep' tln-white

ofniokel

Soft

black Pale-rare

. Earthy; applegreen.

Erythrine, .

of Co.

Co 37

li-n

Fink or peaohblodBom.

Gamierite, .

Silieale

Ni 10-30

Fale-

Apple-green, pala Emerald'eeu,

Silicate

NiB-M

Oiidu

Co 2-15

BUiitk

wad,

ablnisb

ary.

Shade I

Sulphur

A,, Aral

190 pbosfhttiho ror hiiteralb.

Uanqanesk Obbs.

MaagaiieBe is very extensively diBaeminated in nature ; it occnra in veins even in the earliest fbrmBtions, and in irregalar deposits in BedimeDtory beds.

In Tharingia and the Hartz tbeie ores occur ib veins in porphyry, but while in the first region pyrolnaite and psilomelane predominate with heavy spar and other associated minerals ; manganite and haasmannite with heavy spar, Ac, constitute the filling of the veins in the Hartz.

At Romaniche in France an extensive deposit of manganese ore exists forming the cement of a breccia in a rock which is formed by the disintegration of granite and is called "arkoGe." This deposit is connected with a true vem in granite, one &thom wide, filled with manganese ore.

In the Devonian rocka of the Rhenish mountainous reoa deposits of manganese occur in the magnesian limestone or dolomite. Some of these deposite are impreguatioas, which have in part proceeded from a vein ; but the principal deposit consists of nodular concretions in ctay on the aurface of the dolomite The upper beds contain pyrolusite, and the tower psilomelane, the latter ore onginating, no doubt, from the alteration of pyrolusite by percolating waters.

The analogy between the two last deposits is evident, and shows how easily manganeae is segregated. It occurs, even in the most recent formations, in thin coatings which sometimes affect the forms of ferns and are termed dendritic markings.

The principal deposits of manganese, however, are very irregular both in form and extent; large lenticular masses occurring in slate, which, when worked out, give no indications whatever leading to other deposits.

The ores of manganese are extensively employed in the manufacture of steel, but for that purpose they must be free from phosphorus and sulphur. The oxides which are richest in oxygen and poorest in metal — viz., pyrolusite — are used for the generation of chlorine and also for preparing oxygen.

In the manufacture of glass, manganese is used for destroying the bottle-green colour given by iron, and in consequence is termed by the French "avon det verriers" or "glass maker's soap." When cobaltilerons manganese ia used in the same manufacture, instead of a colourless, a blue glass is made. All manganese ores give a violet or amethyst coloured bead with borax before the blowpipe ; and a green mass, if fused with nitre and carbonate of soda on porcelain.

Manoanesb Ores.

Table Of Manganeisb Ores.

Mlnerel

Iot'

Hardapeolflc

8tr8k.

Bemuto.

Pyroluaite, .

Ironblack

Bactllaiy, radiated.

Branuite,

Do.

Brown or brown.

black.

Do.

Browared

HydioM oiide

Doep brownrod

Black or

BaciUar grooTod crystal..

of baryta.

browniafa

-black

Impure

Van.

Vari-

GToyiih-

AmorpbouB nod-able

able

Alabaudine, .

Salphide

Deep green

Rare — colour iron-black— generaUygranular.

Contains leai

Bauerite,

Do.

Reddiahbrown

than akbaodine.

DUUogite, .

Carbonate

Bldidiwhite

Pinkorflehool' oared.

Bhodonite, .

Silicate

Do.

Pink or peach

The last four minerals of the table wUi be eaaiiy known. Although the two Hnlpbidea, being Tare, have not been eBpeciall; alluded to in the determination of minerals, they will be recognised by the reactions of manganese and sulphur before the blowpipe.

The carbonate (diallogite) and the silicate (rhodonite) are conspicuous enough firom their fleshy or peach blossom coloara, and will be diBtinguiehed from one another by their different hardness. Diallogite will be easily scratched by a knife, while rhodonite will not.

An important deposit of carbonate of manganese occurs as irrnlar masses in limestone at Las Oabesses, in France, and the percentage is increased by calcination. Diallogite is not a rsre Htineral in small qnaatities, and its amociatioES are interesting

. It has been fouad with gold, silver, lead, copper, and the other ores of manganese.

Rhodonite is found in some iron mines and also in association with tetrohedrite, and some very beautiful specimens are obtained at time&

Obromiuh.

The only ore of chromium is Chrome Iron, and this ore ia found in many localities, associated with serpentine, but aomatimes its gangne is olivine. The rook dunite, first described from New Zealand, consists of olivine through which chromite is dispersed as grains. In New Zealand and New Caledonia chrome iron occurs in veins, and it is an abundant ore in the Shetland Islands, as in TTnat, &c

Chrome iron exists as large moses in some serpentines, especially those containing diallage, and sometimes aa concretions through the same class of rock. From the decomposition of this rock it occasionally forms a wash or black sand on the sea shore,

' a New Caledonia, in the same manner as titaniferons iron

does in New Zealand. There are extensive deposits of chromite in Asia Minor.

Seintine generally contains ores of iron, but these always contain a few units per cent, of chromium, which interfere with the metallurgical treatment; although, chrome steel is now somewhat largely manufactured, and is of especial value for the heads and dies of stamper batteries.

Chromium is used chiefly in the state of chromate and bichromate of potash in dyeing, and also in the manufacture of colours.

TTBAtnuu.

Fitohblecde is a mineral which is usually massive, black, and with a pitchy appearance ; it is composed of the metal uranium and oxygen, and always contains lead, iron, &c. There are other uranium minerals, such as uranium mloa, &c., which have a characteristic yellowish-green colour, but pitchblende is the permanent ore in depth.

It occurs in several lead.mines in Germany, has been worked as the principal ore in a mine near Grampound Koad, in Cornwall, and ia found in some other deposits. It is used, in the preparation of uranate of soda, which affords a pretty orange colour for painting porcelain and colouring glass, to which it imparts a greenish-yellow, foggy, or opaline appearance.

OHAPTEE XVI. Sulphur — Autimonr — Arsenic — BiBmutli.

IiT some dietriotB snlphur occufb native, associated with gypsum, the most common of the sulphates. It is chiefly found in volcanic districts, such as Sicily, Popocatapetl in Mexico, and White Island in New Zealand. It is also occaaionatl; formed by the decomposition of pyrites, both in coal and metalliferous mines. Its varied applications class it as a raw product of primary importance. It is used for the manufacture of sulphuric acid, and for making gunpowder, and the property which it possesses of expanding on cooling makes it valuable for taking casts of medals, has reliefs, &c

ABSEKia

Native arsenic is rare, but occurs as an accessory mineral in some antimony and silver mines, in crystalline and schistose rocks ; and it is also found in the Kapanga gold mine in New Zealand,

The two other arsenic minerals, orpiment and realgar, were amongst the earliest known minerals, their conspicuous colour, which rendered them valuable for the manufacture of paints, having attracted the attention of the ancients.

Orpiment is a compound of sulphur and arsenic, and has a beautiful golden colour, with a nacreous lustre on the cleavage feces, while that on the fracture is dull or resinous.

Bealgar differs in composition from orpiment by containing more arsenic, and its colour is orange-red. It is often well crystallised, and is aooompaniod by orpiment, into whiidi it changes on exposure. Bealgar is found with orpiment and native arsenic in metalliferous veins, especially those of silver, gold, and lead, in Transylvania. It is also mentioned as occur-

PROBPBCTllia FOB MINBBALS.

ricg in gypeum aad dolomite, aad both orpiment and real&r are often asBociated with prodnots of Tolcanic eruption.

Table Op Sulphur And Arsenic Minerals.

w.

"ffl-

Ss;

Sulphur, Oipiment, .

N*tlve Do.

S,A. S,A.

red

Yellow ; verj brittle. Metillio Initre ; tinwhite or grey. Orsnge-yellow. Deep orange-red.

ASTIMOKy.

The only ore of antimony is the sulphide, known aa antimony glance or stibnite, the oxides which oocnr with it being merely products of secondary formation, while native antimony is rare and ocean mostly with ores of silTer, although it is found with gold in the Wentworth mine in New South Wales.

Although stibnite resembles galena, it will be readily distinguished by being easily fusible in the flame of a candle, by the white fumes evolved ; and by its form, which is generally that of elongated or fibrous crystals ; while galena is granular, or lamellar with cubical cleavages. In some fine-gruned varieties, however, these differences disappear, and the fusibility and other blowpipe reactions have to be depended upon.

It will be more difficult to decide if a mineral is an accidental mixture of galena and stibnite, because it might then be confounded with one of the rare minerals jamesouite, dnkenlte, &o., which are sulphides of antimony and lead.

Both of the oxides mentioned in the table occur either crystallised, fibrous, or earthy, and are products of the decomposition of stibnit, which they accompany in the deposits. Masses and crystals of stibnite are sometimes foiuid coated with a yellow substance, which is rather hard and infusible, and which also occurs in fibrous masses or columnar grooved crystals, resembling fossil wood. This is probably another species of antimony ochre, difEering slightly in composition from cervantite.

Anthnony is generally found in quartz veins, sometimes associated with heavy spar. It is also said to occur with spatbio

iron in beds of Devonian age in Germany, vrbere it is probably connected with veins of tbe same ore.

Stlbnite sometimes accompanies gold at Fichtelgebirge, and in the mines of the Thames in New Zealand, and is itsf auriferous in Portugal, New South Wales, and elsewhere. Although many processes have been devised for treating ores of this nature, no great success has yet been attained.

Table Of Antimosy Ores.

Ooropot iUon.

MetiL Far oent.

streak.

Bemuki.

Native anti. mony.

A amaU lead, 8il-

TlQ-white

Sonietiinei leikdbloe but ganar- tOy tm-wbite.

Stibuite, .

Snlphide

Lead-grey

or steel-

Striated ptuini., fibron* maUM

Valentinite, .

Oiida

or gTBHOlar. White,yeUowiBli, and browoiaii ;

Oiide

YeUowiah. white to

white

nacreooH. Sulphur - yellow or ueotly white,

dish-white.

Bismuth is a metal of rare occmrenoe in nature and, therefore, altliough not used extensively, it has hitherto oomroanded a good price ; but mining on a large scale would soon overstock the market, and create a depression until new applications of the metal were found.

Bismuth is not found, as a rule, in deposits by itself, bnt occurs in Europe with cobalt and nickel ores, and also with silver ores and galena j while in Sew South Wales it accompanies tin and gold, in quartz in which molybdenite is also present.

The principal ores of bismuth are the native metal, of a tinwhite rosy colour and very fusible ; and bismutbine or bismuth

19fl PBOflFECTIira FOB MINBBALS.

glance, which is the sulphide of biemath. The oxid and carbonate of bismuth, known as bismath ochre and biEmathite respectively, are generally found with the other ores by the deoomposition of which they are formed; they occur in the upper parts of the lodes.

The eoB fusibility of native bismuth, its brittleness when cold, and its white rosy colour are ohiiracters which serve to distinguish it readily. The sulphide, bismuthiue, generally occurs in small prisma or in a granular form, is easily sectile, and yields a smell of sulphur before the biowpipe, leaving a pale yellow coating of oxide on charcoal

The oxide forms a yellow coating on the ores just mentioned, and is easily reduced on charcoal to metallic bismuth. The carbonate does not occur crystallised, and will be recognised easily by reduction on charcoal to metallic bismuth and by its solubility with eServescence in acids. The solution will give a white precipitate when distilled water is added to it. Carbonate of bismuth in small rounded pebbles of a yellowish colour is found in New South Wales in some alluvial tin depoaits of the Korth.

In the tin country of New South Wales, at Kingfigate, bismuth occurs in granite and altered slates. The line of junction of the two formations is well defined, and bismuth lodes occur in the granite in proximity to this line, or not more than 400 yards it. According to the late Mr. C. S. Wilkinson, these deposits are pipe veins or oval masses of quartz of variable thickness, descending in a more or less vertical direction in the granite, as though well-like caverns of very irregular shape had been formed in the granite and filled with quartz and metallic minerals. Molybdenite and mispickel occur in these veins as well as tin. The largest mass of native bismuth found weighed 30 lbs.

North of Qlen Innes, bismuth is aasociated with tin in quartz veins of an irregular character. These veins and masses traverse a fine-grained micaceous felsitic rock, which is surrounded by altered sedimentary beds. They sometimes form networks of veins and sometimes masses of quartz, one of which at surface was 40 feet x 20 feet. Bismuth is here also associated with molybdenite, mispickel, and wolfram, and in consequence of this last mineral being present the lodes can scarcely be profitably worked for tin.

The bismuth ores proper — viz., bismuth glance and native bismuth — are always accompanied by the yellow earthy carbonate and oxide, which are products of their alteration and decomposition.

Table Of Bi3Mdth Ores,

Compo..

Uetal.

Hard-cant

.

new.

Native

Brittle, becomes oxidiied by ei. posore to air.

Shining

Baoillar or grann- Ur, aeoUle.

Bismnth ochre,

Oiida

Earthy -yetloir.

Biunathito, .

Carbonato

7B

Oreenltbmy to eoloarleu

n,g,t,7.cbyGOOglC

Chapter Xvil

Combnstilsle HineraU.

Toe minerals inolnded in this group are ell varieties of carbon or hydrocarbons, and are inclnd in the following table : —

Table Of Carbon Minerals.

Hlii.nL

Cbinatm.

Hud-

Graphite, .

Nearly pure carbon

Hetallio Inatre, infusible, MilB the finger.

Coke 82 to 90 7.

bnnu with difficulty.

Coal, . .

Coko 60 to 82

Lnrtre tewnona; bnma

Cumelooal, .

Yield! large qnantitieiof

bnmi freely.

Lignite or

Eydrooi coal

Dark brown atreak ;

blown ooal.

bnmi with a diMgreeable Bmoll. Fraetnre oonchoidal ;

lrbuitfl or

Vol. HydroearbMiB

keroKne lAto or

aotosov.

bnma freely.

Hydrocarbona—

Borne freely with bitnmineral

Carbon . 68 7,

oaontchonc.

Hydrogen 12-5 '/.

or

Idkewax greasy ihams

Carbon . . 86 7. Hydrogen . 14'/;

freely.

Carbon . . 84 7. Hydrogen . 18 7.

"

BamE witb a peculiar

Ambar, .

Oxygenated hydro- Carbon . . 79 7. Gm ... 217,

Eownoua, yeUow ; eleetrio by friction; bnma withanaromaticBmelL

Acphaltnm, .

Oxygenated hydro.

EaaUy toaible; atreak bbuJkorbrovn: bnme

Carbon . . 76 7,

witb a amoky flame

Gm ... 227,

X.B. — Percentages vary, bnt those g1

COUBUSTIBti; KiyEflALS. 199

Diamond is tbe parent form of car'Don. ft is Rombnstible, bnt requires great beat to burn it ; and, being the most valuable of our gems, as well as the hardest substance in nature, is more properly considered in this book with the gems or stones harder than quartz.

The diamond, graphite, anthracite, the coals, lignites, and, lastly, wood aad other vegetable matter alt form carbonic acid Then burned ; but from some of them hydrten and its compounds, especially hydrocarbons, are also evolved, & regular series thus existing through the bituminous and cannel coals to the true hydrocarbon minerals, such as petroleum and mineral wax.

Kext to the diamond in purity comes graphite or plumbago, which is found in the earliest and most highly metamorphosed formations, where it represents the vegetation of those times, which has, under pressure, lost all it volatile constituents, and been also rendered schistose by metamorphic action. It is very valuable when pure and massive, and its wide application in the manu&cture of lead pencils and crucibles is well known. It will be readily recognised by comparing it with the lead of pencils. Inferior qualities have to be thoroughly washed, prepared, and pressed, while pure varieties can be sawn in their natural state.

CoalB. — Ooal seams, as already pointed out, are formed from vegetable matter ; bnt it was while the deposition of the various sandstones, Ac, which overlie them, was going on that the character of the carbonaceous deposits first began to change ; great weight was put upon them, in the first instance, by the overlying rocks and thus they became solidified, and, by means of this pressure, and the heat induced by pressure, chemical action set in, which had the effect of slowly driving off the more volatile constituents of the coals. Water and various hydrocarbons were driven off, and the carbonaceous beds, which at first very nearly approximated to the composition and character of wood, were by degrees changed into coal.

This process of carbonisation is, however, by no means complete, except in s very few instances ; and it is chiefly by the state of clumge that has been effected that the coals are classified as follows :—

Those coals which coatam over 10 per cent, of water have suffered leaa change thaa the others, and they have many disadvantages as compared with the anhydrous varieties. These hydrous coals are sub-divided, by their physical characters, into ligniUs, brown coals, and pitch coals ; but it is very hard to draw a clear and distinct line between them. Thick deposits of brown coal are found in various localities; at Lai Lai, in Victoria, the beds are ICO feet thick and are covered with basalt; and in 2ew Zealand extensive deposits are mined both in the north and south, the seam at the Miranda colliery being 55 feet thick.

When the better class of these hydrous coals are first taken from a mine, they would frequently puzzle any but an experienced observer to distinguish them from the true coala. They have a compact structure, are black utd shining, ajid in many other ways bear a strong resemblance to the true coals. If, however, they be left exposed to the air for some time one has no difficulty in distinguishing them, for they begin to lose their water, and, in doing so, crack in all directions and then fall to pieces. This being the case long transport is impossible, and the employment of the coal must be purely local ; moreover, it must be burned as soon as it is raised from the mine as stacking on the ground will reduce its value.

These hydrous coals, however, are of considerable value where true ooala are not obtainable, and will even compete very favour ably with them when the true coals have to be brought irom a distance ; but they have another disadvantage from the occurrence of water in their composition — viz., that the water is not only unable to supply aay heat itself, but requires a certain amount of heat to convert it into steam ; and for this reason, where both classes of coal are readily obtainable, it is frequently preferable to employ an inferior class of anhydrous coal rather than the best lignite, brown or pitch coal.

The anhydrous coals, as before stated, may be divided into

Anthraoite or non-bitnminons coal, Cnunel or highly bitumiaoiu coal. Steam or household or less bitnminons ooal,

and many other sub-divisions are also made to which it is not necessary to call attention.

Anthracite is coal in which the process of carbonisation has been pushed to its greatest extent. It never contains less than 80 per cent, of carbon, and is frequently almost entirely composed of it. Anthracite does not soil the fingers, and is of a

Combustible Minebal8. 201

glossy black appearance ; it; is difficult to kindle, but in bnnuDg gives off an intense beat with little or no smoke. From the difficult)' in barniog it is not so well adapted for houseliold consumption aa the free burning coals, although it is largely used in America for that purpoee. It is principally employed in smelting metals and raising steam,

Cannd Coal, again, does not soil the fingers, but in other respects differs materially from anthracite. It has received the name of cannel from the property it possesses of burning readily vith a flame like a candle. It is highly bituminous or contains a large proportion of volatile matter, and is principally employed in the manufacture of gas. Although other coals are also employed for gasmaking, tbi quantity of gas obtained from them is generally less than, and the quality always inferior to, that made from cannel.

The ordinary or household coals may be variously subdivided according to the properties which each possess, but the only one of importance is between the caking and non-caking cools.

Caiiing Coala are those from which, in burning, there exudes a black bituminous substance which cements the coal together, in the fire, into a pasty mass. This class of coal is the one from which coke is chiefly made, and is also used both for domeetio purposes and for raising steam. The other, or non-caring coals, do not run together when heated, and are of a more free burning character.

Jet is a variety of coal, is black, and takes a good polish. It is of value for the manufacture of ornaments, such as crosses, earrings, &C. The most important deposit known is that of the Jurassic coal measures, near Whitby, in Yorkshire, where two <fualitiea are found, one very hard and valuable, another softer and of less value.

The bog oak of Ireland must not be confounded with jet ; it is simply wood impregnated with iron, and occurs in swamps where iron ore is forming at the present day.

The name of jet is commonly given to black glass beads and glass jewellery, but these are not likely to be mistaken for the

genuine article. Jet is much lighter and not so brittle ae glass, ut its origin does not appear to be well understood. It is described by some authors as a variety of lignite, but it is anhydrous, and is generaiiy associated with cannel coal ; it is very probably a fossil gum. Jet occurs in the Hartley Vale and Joadia Greek shale mines in New South Wales, as thin seams which have no great lateral extension.

D,g,l,.9cbyGOOglC

PROBPBCTIKa FOR MlNSRtlA

Fetrolkuu.

Fetroleum is composed of hydrocarbons, and ia found ia rocks of all ages, sometimes in subterranean reservoirs of great extent

In Pennaylvania, sandstones saturated with oil, form the reservoir, and these sandstones appear to be lenticular in form, and of varying texture, sometimes passing into conglomerates. The following facts appear to have been ascertained with reference to the Pennsylvania oil region.

1. The thicker the cover the more the oil, large accumulations being seldom found under light covers.

2. The coarser and more open the sand the more the oil.

3. The sandstones buried in Bhales must form the reservoir.

4. Underlying shales must exist which form the source of the oil.

In the Ohio district the Trenton limestdoe, which is struck at a of from 1100 to 2200 feet below the sur&e, and is covered by dOO to 1000 feet of shales, appears to be both the producer and reservoir. The principal accumulations, both of oil and gas, are always in the uppermost beds of the limestone, and generally not more than 30 or 30 feet below its upper surface. The oil rock coutiaaes to a lower level, but below the oil the rock is charged with brine containing unusual quantities of chloride of calcium and mipesium ; when this is struck the well is frequently lost, although it is sometimes possible to plug it near the bottom.

The limestone appears to be quite porous in parts, but this porosity seems to De due to dolomitisation, the change having resulted in recrystallisation which has left innumerable microscopic cavities in which the oil has accumulated.

There appears to be no doubt that petroleum has been derived from organic matter and much more largely from vegetable than animal substances ; it has, moreover, been produced in most oases at the normal rock temperature, and is aot a product of destructive distillation of bituminous shales.

Where flat anticlines exist, the paying wella are almost always on the domes, whether these be the main ones or those of smaller elevation situated at points in the synclines. This is still more the case with gas wells, and where gas and oil have been struck at other points they are, very generally, soon overpowered by salt water.

Petroleum has generally been found in consequence of a discovery of inflammable gas, sometimes escaping from fisiurea

Cohbustiblb Uihebals. S03

in tibe surface of the ground, and, in other cases, struck when sinking wells. In some instances this gas occurs in vast quantities, and has been used extensively for heating and lighting purposes.

The disDOver of indications, however, affords very tittle information as to the best localities for sinking wells, and in the early days of an oil field there is a great deal of chance in the location of a site. When, however, several bore holes have been put down, information is gained which serves as a guide, and fewer mistakes are likely to be made.

Some oil-bearing rocks, such as the Boghead mineral or torbauite of Scotland, and the similar oil-bearing shale of New South Wales seem to have been formed in a similar manner to coal, but under difierent (xinditions.

'tiie last rock, known as "kerosene shale" occurs in lenticular beds of considerable extent in the coal measures and probably differs only from coal itself by being composed of the remains of swamp plants, which have undergone decomposition under water, in special conditions capable of preserving moat of the gases. If microscopical examination does not detect any organic structure as in coal, it is most likely because the water plants were of a much softer nature than those which formed the ooal, and that the cells have been completely destroyed by fermentation.

An abundant source of petroleum is to be found in the oilbearing schists, or, as they are sometimes incorrectly termed, bituminous schists. According to Dufresnoy tlie oil in these schists originates &om the decomposition of animals, especially fishes, the fossil remains of which are abundantly found ; but this, if true in one instance, can hardly be considered as universally correct. Petroleum occurs in different formations, from the carboniferous to the tertiary.

Mineral wax or oaokerite is a solid petroleum containing from 14 to 15 per cent, of hydrogen, whilst petroleum contains 16 to 17 per cent.

Mineral caoutchouc or elaterite contains still less hydrogen, from 12'3 to 13'3 per cent., than mineral wax. It is found with lead ore and calcite at Castleton in Derbyshire, and in coal mines near Nantes in France, and also in Maseachussets. A similar mineral has been found in the Coorong Lagoons of South Australia and named Coorongite.

The bitumens contain 10-3 per cent, of oxygen and hydrogen, and when bitumen regularly impregnates rocks of somewhat homogeneous composition, such as limestones, it forms a material

which IB highly prized for footpaths, flagstones, &c. For that purpose it is crushed to powder, melted, and nsed either with or without additional sand and pebbles. When refined in powder it can be set dry and agglomerated with hot irons,

Ambvr is a mineral resin and, like the bitumena, coatunji about 10*6 per cent, of oxygen and nearly the same proportion of hydrogen. It resembles kauri gum very closely, audi oma ments are made of that substance to imitate amber, bat they are more brittle than the geaoine article. Amber, as well as kauri gum and other resins, has exuded from trees, and is frequently found fossilised in lignites of Tertiary age.

Chapter Xviii.

SENEBAL BINTS BEtTABDINO PHOSPeOTIHa

H&TING now described the modes of occurrence of minerals which are most common, and the means which are best adapted for distinguishing one mineral from another, it only remuns to give a brief summary of the operations which are necessary for the prospector to adopt for the discovery and tracing of ores, together with such development as may billy be expected of him, before the discovery is in such a state as to induce capitalists to provide sufficient money to open the mine.

The student may expect some hints regarding the outfit he will require and the operations he will have to undertake, but there is little that can be said which will be of much use to him. With the exception of the few blowpipe accessories which have been enumerated, a compass, and a small prospecting pick, he will be able to secure any equipment he may find necessary at the nearest store, from which he also obtains his provisions ; and so he will avoid being encumbered with tools, tents, &c., until he has actual need of them.

Equally is it the case that no description of the methods of sinking shafts and diving levels will be of much use to the student who proposes to work in a practical manner, for a week's residence in a mining camp will afibrd him more information on these subjects than he could obtain by reading, and he will generally find it to hie advantage to do a little work on a claim before starting out to prospect on his own account.

It may be well to recapitulate a few points which have been already alluded to in the foregoing pages.

MeUils and minerals may be found either associated with the

OENEKAL HIST8 BBOABDINO PEOaPKCTING. 205

rocks'in which they were originally deposited, in which case they are called " tnineral deposits," or, having been worn away by the action of the weather and transported by running water, they may occur associated with gravels and sand in existing streams or buried river channels, in which case they are spoken of as " alluvial depoeits."

The metals and minerals that are found in alluvial deposits are few in number, and for all practical purposes may be limited to gold, platinum, tinstone, and gems, although certain rare minerals, such as osmiridium, are also found now and then.

Owing, however, to the great value of the minerals mentioned above miich are found in alluvial deposits, and the fact that a very large proportion of the gold which has been won during historical times has been obtained under these conditions, alluvial deposits demand very careful attention. They are of the greater importance to the prospector because, in many coses, alluvial gold and tin are found under conditions which require no capital to work them, and, consequently, immediate returns can be obtained when the discovery has been made.

These alluvial deposits have been described under the chapter devoted to this subject, but some remarks regarding prospecting for them will be of value, and it must be understood that it is assumed that the district being prospected has not been previously tested.

River beds and creeks should be carefully examined, a pick and a shovel, a tin dish, and a large knife being all the equipment necessary. lu the first place, the gravels of the streams should be washed cai-efully with the object of determining whether any gold at alt exists. !Next, certain beaches along the course of the stream should be selected (see p. 132) and shallow pits sunk through them until bed rock is met with, and all the material i-aised should be panned, bearing in mind that the best gold is generally found on the bed rock.

A further teat should be made by carefully following up the stream, especially when it is low, and cleaning out with a knife all crevices in the rocks in which gravel and sand have accumulated, and this should all be panned. In some cases, very large quantities of gold have been saved by prospectors in a short time from " crevicing " in this manner.

In certain dry countries, as, for instance, in Western Australia, the rainfall is not sufBcient to carry the gold broken down from the reefs for any distance. In such cases there ate flats of greater or leas extent in which gold occurs through the surface soil for a depth of a few feet.

Where sufficient water ia available to wash these deposits, very good returns can frequently be made, and, indeed, a large 4jnantit7 of gold has been saved by "dry blowing." Ilie most priniitiTe system adopted is, after the larger stones have been screened out, to hold one dish shoulder high, and gradually pour the auriferous sand into another dish on the ground, the wind blowing away the lighter particles and allowing the heavier gold to fall into tiie dish. This operation has to be repeated several times ; but it will be evident that by this method of treatment a good deal of gold must be lost, and also that what gold is saved cannot be properly cleaned ; so that water will be required for the final operation.

Deposits of this class are most usually discovered in the first instance by nuggets of gold being picked up accidentally on the anrface, but when one or two of these have been found, prospecting by dry blowing is often resorted to over considerable

Tbeee surface deposits must neceaaarily exist in the vicinity only of the reefs or lodes from which they have been shed, and their occurrence aSbrds considerable inducement to prosjiect for reefs in the immediate neighbourhood ; but the gold whii ia found in rivers and streams does not necessarily point to the lo3e proximity of the reefs from which it was derived ; still lesa does the occurrence of alluvial gold in buried river beds indicate the proximity of reefs.

It is very difficult to enandate any rules for prospecting for these buried deposits, but a careful prospector will often notice that a river or stream which he is testing, appears at certain points to have altered its course ; having, in tact, found it easier to cut a channel in a different direction to that which it originally followed, it has done so leaving its former channel, with the gravels and sands it hod deposited, high and dry.

In cases such as this, it is generally worth while to sink prospecting shafts through the gravels until bed rock is reached; and, if the first is not successful, others should be sunk towards the deeper part of the channel as defined by the inclination of the bed rook where It is met with. There are, of course, comparatively few prizes and many blanks in prospecting such as this, but the value of the deposits found at times, offers inducements to prospectors to continue trying, even when but small success has attended their earlier efforts.

Perhaps the most important point with which the alluvial prospector has to make himself acquainted, is what value of ground will pay him to work, and as regards this no information of any

Gbneral Bints Regarding Prospegtihb, 207

vorth can be given ld a book, seeing thut conditions vary in each particular case. He will, however, very quicfclj discover how much gold he can extract in a day with the means at his command; and, comparing this with the coat of living and the time he has had to expend in sinking his shafts ; taking into consideration, moreover, the amount of ground that he is able to hold in compliance with the laws of the country, and the area that can be worked from each shaft : be will be enabled to form a very accurate idea of what the claim is worth to him.

There are many cases in which the amount of gold found ia not sufficient to pay the individual miner to work, but in which, if concessions of a large area can be obtained, and a water supply can be secured sufficient for all requirements, a judicious expenditure of capital for working on a targe scale will frequently well repay the cost. Under most favourable conditions, wiw practiciJly unlimited water and a sufficient space for the deposition of tailings, as low returns as 2. per cubic yard can be made to pay handsomely.

The occurrence of alluvial gold or tinstone leads the prospector to examine the country for the reefs from which these have been shed, and a careful study of the conditions which prevail will afford much information. In the case of surface deposits, it is evident that the country in the immediate vicinity should he examined ; but where the alluvial deposit has been found in the beds of existing streams or old river channels, it ia equally obvious that it may have travelled a long distance from its parent ree£ Under these conditions it is necessary to find out whether the alluvial deposits that have been worked are of primary or secondary origin ; whether, in fact, they have been broken directly Arom a reef and have not travelled very far ; or whether they have only been safficiently enriched, by natural sluicing of poor drifts in cross drainage channels, to enable them to be worked to advantage

In the latter case, the occurrence of alluvial material is no guide whatever as to the vicinity of reefs ; but in the former case the stream should be carefully followed towards its source, and the gravel panned irom time to time to test how far up stream the gold or tin exists.

So soon as the amount of tin or gold falls off appreciably, the hills on either side of the stream should be examined, which, if they are barren, can easily be done ; while, if they are covered witj) soil and timber, it wul be necessary to sink shallow pits or cut trenches in order to lay bare any reefs or lodes which may exist; the soil cut in these shafts and trenches should also be

panned constantly in order to prove whether the right direction ifl being followed.

When pieces of copper, lead, zinc, manganese, or other ores are found in river beds or on the surface they should be traced in the aatne manner, always following them up stream as Ions as any pieces of them can be found; and, afterwards, the hills should be examined until the lode or other deposit is discovered from which they have been broken.

It is, of course, often the case that, notwithstanding all the . care that is exercised in tracing broken mineral to its source, no deposits of value are found ; and it is equally true that most of the important mines of the world have been discovered by accident ; and in many cases by people who have been quite ignorant and wholly unversed in the value of ores. Even, how. ever, if this is the case, an accurate knowledge of the nature of ores and the ability to recognise those which are worthy of attention, places the trained prospector at a considerable advantage, and enables him to utilise chance discoveries made by others who are not so qualified.

An outcrop of mineral having been found, further investigations are necessary to prove the nature of the deposit, le strike having been determined, in the cose of a lode, it is first advisable to test it along the sar&ce at various points to prove its continuity and comparative richness at different points. Bearing in mind what has already been stated regarding the existence of shoots of ore, it must not be assumed, because a lode is rich where found, that it -will be equally so at all points where it is intersected ; and equally, because a lode is poor where first discovered, there is no reason to suppose that further surface prospecting along its course may not disclose parts in which valuable mineral occurs.

It will be within the knowledge of every prospector, even of those with but limited experience, that when a lode has been discovered which carries valuable mineral at its outcrop, other claims are marked out along le course of the lode at either end of the prospector'a claim. While this is a perfectly legitimate undertaking, it must be borne in mind that these " position blocks" have only n prospective value until the continuity of the lode has been provM, and until it has, moreover, been demonstrated, that it also contains in the ground secured, mineral of sufficient value to pay for extraction.

When surface-prospecting has given as much information as possible, some sinking and driving should be undertaken to prove the continuity and value of the deposit in depth, and here

General Hints Reoabdino Prospectinq. 209

it is important to emphasise the fact that a proapeotor'a busiaeas is to prove, at as small an expose as possible, the value of his disooverf, and not to prepare a mine for the ultimate oheapeet method of extracting the ore. It is the more important to insist upon this point, because in numberless cases, a lode having been discovered on the surface, the prospector sinks one or more vertical shafts; so located as to strike the lode, if it conlinnes downwards, at a depth of, say, 100 feet &om the surface, the shaft being sank through barren country rock, and proving nothing w£ttever until the lode is intersected; and, even then, it is only proved at the actual point of intersection, where it may be abnormally rich on the one hand, or on the other so pinched and poor as to offer but little inducement for fiirther work; many good properties have been abandoned by the original prospectors owing to this having happened

To acquire the greatest amount of information at the minimum cost, the point should be selected on the surface where the reef is at its best, and, having determined the extent along the strike, as nearly as possible, which carries payable miner, the shaft should be placed about the centre and sunk on the underlay to a depth of 100 feet, or less, if the water level is reached sooner ; and, &oni the bottom, levels should be driven along the course of the lode as long as the mineral is of sufficient value to pay.

It will be seen that by these means a block of ground can be cheaply opened, in which a certain quantity of ore can be measured and sampled, and an accurate idea of its value obtained. In measuring up quartz it is usual to estimate 13 cubic feet to the ton, in tiie solid, so that a vein 3 feet wide proved to a depth of 100 feet, and for 100 feet along its line of strike would contain IW " 00 x 2,307 tons.

The stone should be sampled every few feet and taken from wall to wall in order to arrive at a fair estimate of its value.

In following up other minerals than gold, it must be borne in mind, that many of them have a tendency to decompose when exposed to the action of the weather, and, oonsequently, that the nature of the ore at the outcrop may be very different to what will be found in depth. Copper ores, for instance, are very liable to decompose and, forming sulphates which are soluble, to be carried away in solution by running water. As most copper ores are associated with a greater or less quantity of iron (see p. 165), the outcrops of copper lodes are very frequently represented by a porous ironstone, which is called

" gossan," and no sign of is found until soma depth hai bn sank. Qenery spewing, an ontcrop of porous gOBsara may be looted upon as a very good indication for mineral in depth ; whereas, a dense ironstone seldom leads to rich deposits of other mineral below.

There are certain points regarding the nature of the rooks which should be borne in mind ; for instance, tinstone is never found at any great distance from the junction of granite with some other rock, generally state (see p. 175) ; moreover, the otaas of granite in which tinstone oocnrs, is almost invariably one in which white mica forms an important constituent of rock. Oopper ores are in most casea associated with rocks of a dark green colour, snob as diorite, <ko,, and some very large and important irregular deposits are associated with serpentine (see p. 169). Lead ores are largely associated with limestone formations, as also are ores of zinc ; but, while all these points are worthy of attention, they must not be taken as forming any invariable rules.

Many of the irregular deposits to which attention has been drawn in the earlier pages of this book are of great value, and certain of the rarer minerals, sach, for instance, as sulphide of bismath and native bismuth are found in these deposits. A. few remarks regarding the work of prospecting these will be of importanoe.

These irregular deposits are not only irregular in their mode of oocnrrenw, bnt vary indefinitely both in size and shape ; so that no one by surface indications is able to form any opinion regarding their extent. It is even more important in testing these deposits when an outcrop has been found, than it is in the cose of a ree to follow them carefully in the workings. Any drives or shailH which may be commenced should follow the direction of the ore, no matter how crooked this may be, as it will be quite time enough to sink vertical shafts to work the ore, after its extent has been proved as far as possible by these prospecting works. To sum up the question of development work which should be undertaken by proctor, it may be said, " When the ore has been found, fdkiw it ! "

There are a number of minerals of value which hardly come under the heading of ores, such, for instance, as the nan-metallic minerals which are used for industrial purposes. Amongst these may be mentioned witherite or carbonate of baryta, apatite or phosphate of lime, alnnite or alumatone, fluor spar, and scheelite or tungstate of lime, all of which are valuable if found in conaideraUe quantities and in easily accessible positions. Even

QEMEBAL HIHTB BBaABDIHO PB08PKCTINQ. 211

the better Tuietiea of m&rb1e, gypsutn, and lithographic atone, which occur u rooks ; are worthy of some Mtention when well situated and of good quality ; and deposits of ironstone, chromite, or manganese area are all of value, if situated in positions which enable them to be shipped at low prices, and if they are sufficiently rich, say over 50 per cent, of the metal or chromic acid, to allow of their ready sale. The questioa of locality, however, ia ooe which enters largely into the value of deposits such as these, and the best deposit of manganese with a long land carriage would be valneless and not wortiiy the attention of the prospector. In localities difficult of access, none but the most valuable ores are worthy of attention ; and, generally speaking, it is only in the pursuit of gold or gems that such districts ore likely to be prospected.

Nothing need be added to what has already been said regarding gems. They are nearly always found in alluvial drifts, indera, the diamond bus only been traced to its parent rock in S. Africa. In prospecting any alluvial drifts it thus becomes a matter of importance to carefully examine any of the heavier stones found in panning, to soe whether any of these valuable minerals exist.

Gold and silver frequently occur under conditions which render it impossible to recognise them, and estimate their value, exoept assay. Gold, for instance, is very frequently associated with pyrites, and, where this is suspected, it is better to roast the finely crushed ore as long as any smell of burning sulphur can be detected, after which the gold can generally be seen in the pan ; but it is necessary even then to assay the ore to determine what quantity of gold is present.

What has been said about gold is even niore applicable to silver, for this metal seldom occurs in a native state, bat is generally associated with galena or other lead ores, or with grey copper; although, of course, there ore important deposits in which chlorides, snlphidea, aatimonides, Axs., of silver occur. No estimate of the value of an argentiferous galena can be formed, except by assaying ; consequently, oil ores of this class should be BO tested.

The practice of assaying gold-bearing quartz, as a general rule, is not to be advocated j as the returns ore generally misleading, owing to the difficulty of taking average samples, and the fact that free gold is never equally disseminated through the stone, but occurs in grains, strings, Ac, the rest of the stone being abeolately barren. In sampling pyritous ores or lodes carrying galena, for purposes of assay ; indeed, in sampling any ore with

the object of making chemical tests regarding its contents, it is necessary to take as large samples as possible. These should be taken from all parts of the lode exposed, and, after having broken the large sample thus obtained to an uniform sise, the material should be well mixed and quartered, that part selected beiiu; crushed finer again ; and ao on, until the last lot from which the sample for assay is taken ahoiild be reduced to powder. In ampliDg an ore in which the percentage of pyrites is comparatively small, it is frequently better to crush a &ir quantity of it fine ; and, having taken a weighed quantity, to concentrate by panning, and only to assay the concentrates. Of course, if thu is done the weight of the concentrates obtained must be taken, and the assay results apportioned to the whole ore.

The methods of tracing coal have been so fully dealt with elsewhere (see p. 81), that it is hardly necessary to make any further remarks on the subject. It, therefore, only remains to recapitulate as briefly as possible a few hints for the guidance of prospectors.

It is obviously necessary that some attention should be devoted to mineralogy, not in the sense of distinguishing all the numerous varieties of minerals which exist, but the prospector should be able, by simple blowpipe tests, and some knowledge of their physical characters, to recognise with accuracy the more important and common minerals. Wlienever he finds a mineral which he cannot recognise himself, it is always worth while keeping a specimen, and noting whence it came, for subsequent determination.

He should also make a study of the associations of minerals, noting the usual combinationB which occur, and which have been alluded to through this book. The minerals which may be mistaken one for the other should also be carefully studied, and the tests which serve to distinguish them. The natures of the different classes of rock are also of importance, and every possible information should be stored in bis mind regarding the mineittls which occur associated with them in other localities ; and, finally, so much stratigraphical geology should be known as to impress upon him the fact that the age of the rocks in a new locality has nothing whatever to do with their mineral contents.

Above all other things, however, the prospector must be practical, and must avoid forming theories until he has sufficient grounds from actual observation to support them. He must test his ground carefully, and examine all the details, which bear upon the question, dispassionately, with the object in view of

GKNEBAL HINTS BEGARDIHG PROSPECriNG. 213

proving to himself whether, or ao, any discovery he has made poBsesaes the elements of a eucoessfal mine, if followed up. It is always an impleasant thing to relinqaiab an undertaking which has been commenced ; but it is much better to do this at once, when it is apparent that it will not pay, than to continue working an nnprofiteble affair.

The prospector has always to be careful not to deceive himself and not to be led to conclnsiozis which he desires to form, if they are not supported by facts; and this is perhaps the moat difficult lesson of all which he has to learn, and one which is sometimes never least satis&ctorily. It should therefore be always remembered that, although every prospector must be sanguine of ss, his hopes must be tempered by judgment.

n,g,t,7.cbyGOOglC

n,g,t,7.cbyGOOglC

Glossary.

ATJHJfcf TR,

Aldkiha,

ALU£ITIC, .KALCAll, AJUIAAKATIOH,

Ahoxphoitb, . Ahfhiboijtb, Ahioduoim,

ANALona, . ANAUsm, . Amdalubiti,.

Bvdnced to powder. L bodyoor

A vaaety of hornblende, see p. 60.

DiAmond-like.

tiillcate of olnmina And potwli ; variety of

orthooUw. Silica — miitoras of ohnloedoBy in layere with

jwper, Amethyit, or qotutz. A ooherant . Snlphide of nunganMe, Hydrous ralphate of Uma — a oompact fonn of

gypvxw, Siiktle (rf aliusmA And lodR ; a fdipar. Hydrkta trf potMdnin, sodium, lithitun, and

Nobk gAmet.

A BolpbAte of AluminA And nthar potub, loda, BDnnoiiiA, magneaiA, or iron i aolutile in water. Oxide of aluminium. I A metallic element.

Sulphate of Alumioa andpotaah ; a aonrcs of alum. , A lilver ore conaiatiiig of dlTc and mercury. , Intimate miitora ; naed to daacribe the absorption of gold by merouiy and tha methods of effecting this abmnption. . A foatil gam.

, fflUoA i A purple TAiiety of quarti.

, Having no definite cryitalliiie farm or structun.

. Hornblende rock.

. Small almond-ahaped vnicnlar cavitiea in certain

igneoUA roolu, partly or entirely filled with

other minerala, . Hydioui iilioate of alomina and loda ; zeolite.

A variety of baialt of medium textwe. . A silicate of alumina.

Qlobsary.

.

Amomwti, .

. Sulphate of lead.

Ashtdeous, .

. Silkkte of alnmiiu And lima; a felspar.

Anthuoitb, .

Asticusx, .

. A saddle back; applied to strata when bent lib the roof of a ouw.

Aimiioinis, .

Amiiotii, .

. . A silicate of almmiia and gludna; a variety of beryl.

AsGINTiyikUOUSi k

. SUtst beAricg.

Akkobb,

. Oompoundi of antonio acid with bAKi.

Absbnio,

. A metallio elemeoL

Absinidis, .

. Compound of araenio with metal*.

Auoin, .

Airaimi . .

. . Grouped in bundle* like rticlu.

Backs, .

. . The ground between a level in a mine and the

next workings abova, or the mrfaoe.

Back Leads,

. . A term to black >and "leave" on coast lines which are above high water mark.

Bamsbd Vbiks, ,

. . Tdne made up of Uven of different minerali

Babmn, . . Babttes,

. Auriferona conglomerate! cemented together with qnartE.

. Carbonate of buyta and lime.

Basalt,

Bbddid Teihs, .

Bebtl, .

BuKOTB Olamoi

Veins mnnins ptu'allel with the itnta in which

they occur, both in itrike aiid dip. Stratification; ths arrangBment of atnta in layvi*. rock underlying loose or incoherent

stnta, mob u AllnvuJ dflpoaita. The thinner labdivuioiui of Mdimentaij rooks. A ulioate of almnina and ghidna.

A metallic element

Sulphide of binnath.

Oxida of biamutb.

Hydroni carbonate of UmiDth.

Fitch or tar.

ContainiiiK pitch or tar.

Aiillaceoiu carbonate of

a with Utnminoai

Bimni,

. SulpbidB of rinc

. A dark gFeeii variety of qnarU with apeak* or

veini of jaapar.

. An inrtniment to caat a current of air throu

aflame.

. A shale oontuning a large percentage ol hydro-

. A borate and chloride of magneei

BOEAl

. Aborateofeoda.

Bobino,

. Sinking holes by mean, of rodi or dianuHiddrilla.

. Like a bunch of grapes.

BOITOll,

. See Falte BoUon.

. Sulphide of lead, antimony, and copper.

BBAonm, .

BHAEtUAS EHSAALD, .

„ Sappho ,

„

Bbkwia,

Bboiiaxqtbitb, .

Water impregnated with salt.

Bromide of silver.

A compound of bromine with a metaL

Baonzm,

Bbookh

Qlosbabt.

Bbowk Coal,

. Lignite; bydroiu oenO.

Bbows Ibon Obi,

BUHIXD HlVKU,

. BiTerbedi which hare

Oadmidk,

Cai.Aiiihi,

. TeUntida of gold.

Oaloabkhtb,

Snnro,

. CbIcamoiu deposit from watt.

„ Tufa,

Cawibation. .

Oalottb,

OALonm, . .

. A metallic element

Oaloiol, ,

OAmiL Goal,

. Hit-lika.

Capilubt, .

Cabat, .

. Sitroygruni.

Garbokio Aoid, .

. Cubonic anhrdride OOt.

Cabbohisatioii, .

. Converaioii to carbon.

Oasnallti .

. Ohloride of magnesia and potuh.

Cabino, ; .

. Ckyra' material foond betmwn a vein ind ila

. Oxidaoftin.

. Oriental eafa ejre U ohiyKbrrl and fal oat-i

je quutE enaloting fibni of asbertoa.

. A diagonal lode.

CEuenui, . .

. Sulphate of Btrontia.

Cement,

. Carbonataoflead.

. Oxide of antimony.

. Hydrous gilicate of alumina, lime, potash, imd

soda; a leoUte.

OBALOAMTatr .

. Snlphate of copper.

Chalqbdoht, ,

. A variety of qrti.

Cbalcoftbiti, .

. Sulphide of ooppec and iron.

Olobsabt.

Chlobine, . Chlobti . Chlokobboiodib,

Curohb Ibok,

Cbrohitb,

Oobokhk, .

Ckbtbobkbtii, Cebtboooua, Chbtbolit . Cbbtbopeu

Cut, ,

Olii Slate, . Olbivaqb, .

Cobalt,.

Cobalt Bioom, . COBAtTiraBODB Wad,

COBALITFEBOCB MlBPlOKBL, COBALTDra, . COLVHHAB, , ,

Ooubustiblb, Conohoidal, .

Silicate of alumiaa, Aneside of niokeL Compounds of ohloiine with metslH. , Convennon of sold into chloride of gold by tha action of chlorine. An element.

A hydrooB dlicte of nufneffiA and almuinit. Componnds of chlorine and bromine with metala. A ohromate of iron.

A metallic element.

Aluninate of glucitia ; a gem.

A hydrous nlioate of copper.

BiHcate of magneua and inm.

An apple-graen Taris of qnartc

Hjdnnu rilicate of magneuA ; a fibrous rariet;

of ierpntiBe. Sulphide of memuy. False topic; a yellow vaiiety of quartz. A h;diated ailioate of in very finely

divided particles. A slate formed by the induration of oUj,

The

he property powessed by certain. mineralB a: RKUcs of splitting more directioiiB than others.

The planea along which oleafage bakes place.

An inBtraaieiit for meagnring aoglea on a vertical wall face.

FoBsilised carbon formed by the oarbonigation of vegetable matter.

A metallic element.

Aiseniate of cobalt

Impure oxide of manganese, conlaitiiDg oobalt.

Sulphide and arBenide of iron, contuning cobalt.

Sulphide and arsenide of cobalt.

In the form of columns.

Sae Banded Veitu. Capable of bring burned. Shell-like.

n without n A term applied to rocks in irtiich lodes become

ore-bearing. Consolidated graveL Mineral depoeitB oocurring at (he tine of junction

oftt

I dissimilar rooks.

OONTOBTIOir, .

COFFEB, CatFSBjLB, .

CoppBB Slate,

Copbolitm, .

Cobdibbitr, . Cobukdum, . Cotebhinoits,

Ckadu,

Ob&tb Dau,. Oraiiufob,

Orztaobods, . Obevioino, ,

Obocidolitb, Obocouit . OiOBa Couaa

Cdpbiti .

QLOBSABr.

CrampUng and twisting; A metallic clement. Sulpirte of iron. Sulphide of copper. Anenide of nickeL Sulphide of copper and iron. . Slate impregnated with coppar nineniilB.

Phosphate of lime; petrified ezcrementi of

animBlik Silicate of alumina, iron, and magneda ; a gem- Alumina; a gem. Finishing at the same poiuL Deporits of ore in lodee haviiig a small vertical,

batconsiderebU lateral, eitent . Sulphide of copper. An (ipparatui for washing alluTial gold, mounted

, A dam built of crate with Etonea.

In the form of a crater. , See Qeologicai Taite.

Searching the crevicea in rooks forming the beda of streuna in Karoh for gold.

A fibrous silicate of iron, soda, and magnesia.

Chromate of lead.

A vein interaeddng another of greater geological age, which it &equentl7 duplacea from its original course.

fluoride of almnina and soda.

The assumption by matter of a definite geometrical form.

A soliS six-sided figure, of which eaob of ttie HtdeB is a square and all the BSglea right angles.

Red oxide of copper.

A silicate of alumina.

DkAD WOEB,

Dbobzfitatb,

Decrasatioh,

Dzl7DBinOj .

Dbnudatiom,

Work in unproduoKve ground.

IS buried below

Wearing away. Deprived of water- Like broDcbes of trees. Stripping by water and other agents.

Devonian, Diabase,

Du.Toh3,

DioBirr, Dip,

Dislocation,

DisTaitr dolbbitb,

dolohitb,

dohsikite, . Deedoino,

Dei Omk,

£labtio, ,

Eleuhis, .

Eletatioh, .

Olossart.

8m Geological Table.

An igneoiu rock, Bee p. 9

A lulicate of lime and m

Carbonate of manganese.

CcystaUiasd carbotl ; a gem.

Minute plaata wtiich are provided with BUiceous

envelopes. Exhibiting two different colours when light is

ifsuamltted in two different directions. Cordieiite ; a silicate of alnmina, iron, and

ii every direction

A BilioAte of lime and magnesia.

A silicate of copper.

Ad igneous rock, see p. 9.

The angle of inclination of beds or itrata

meastued in relation to a horizontal line. The breaking asunder of goHd matter due to

chemical or physical forces. The displacement of rocks on either side of a

Cjranite ; a silicate of alumina.

An igneous rock ; see p, 9.

Carbonate of lime and m

Strata which are dipping away in

Arsenide of copper.

Rtusing material frau below water by means of

Loose crumbly alluvial depotdte. Cavities in rocks lined with crystals. . Silver ores which do not conttun lead. Caple of being drawn into wire. A space below place of delivery where tailings

can be deposited. A massive olivine rook in which email grains

of chromite are intenipersed. A vertical or hhly dipping injected sheet

of eruptive origin.

Cryetala or powder formed on the surface of minerals, due to their decompositioD.

SabstaDCes cable of being stretched and then resuming their original form.

Elastic bitumen ; a hydrocarbon.

An alloy of silver and gold.

Substances which have m

A front or side view of anything.

An igneous rook, ss* p. 9.

Ehibi.

Epcxhb, Epsom Sut, Ebodihii,

Ebitbbihk, . exobvoehck, expolutv, ,

Fahlbandb, Faub BcrrroH,

Flooah, Fluob Spab, . FooTWAU, .

Fobsiufbbocs,

Olossart.

ChloTobromide of ver. A ulicate of alumina and glncinai a gem. An impure variety of ooiundum. Sulphide, knenide, and antimonide of copper. A ailicata of nutgneaia and iron. . See OeotagiaU Table.

A hydrous iQicatfi of alumina, iron, and lime.

Hydrous sulphate of magnena.

Gradoally wearing away.

Bomite ; lolphide of copper and iron.

Formed b; a violent breaklDg out of encliieed

Annoiate of oobalt.

Brown out of.

To peel off in leaves from the outside.

Zonea of crvtrtaUine Bcbista impregnated with metallic sulpbidea which influence the liohnen of lodea paedog throogh them.

a accompanied by a

. Anhydrous ailicatea of alnmica and of au alkali

Containing iron.

CoosiBting of fibres wliich caimot be easily

separated. A silicate of alumina tliat will stand intense heat ; it is almost entirely free from alkalies or lime. . Opencncka. , A lode occupying what waa once a fiasure opened

by a movement of the rocks. , A horizontal ore deposit occupying a bedding

plane in the rock. , Cloudy, resembling lumps of wooL . The bottom of a coal seam. A soft olayey mbstiuice, casing. Fluoride of lime.

The lower side or boundary of a iode, . Bocka containing f osols. The remains of plants or "innl acuidetitally buried in tiie earth. , Olide of iron, dnc and manganese.

Ores which jdeld their gold or mlvet to amalga-

. A sulphide nlTer, lead, aod antimony.

a LOSS A Hr.

Oabbbo, Oalkna,

Q-ANom. Gabhrb,

Gblatinibb, Gboloqioal Tabl

Qbrsdobfihb, Glaoial DcroaiTS, Qlaohb Dnouifl,

QlAOBKR Balt, .

QLADOOIWra,

An igneous rock, we p. 9.

Sulphide of lead.

A Milicate of ana.

The matrix in a lode in which ore oociin.

AnhTdroua silicatea of KlaminB and the earths

coltmred by ozides of iron, inAii[;aneae utd

chromiQin. A delicate of nickel. FinmreB which ftre oonSned to partioalar rocka

or beds and which do not extend into adjoining

Domeabaped bendinzs, not only of tba atntta or formation, but of the earth'j crust covered with ita strata vbich msj or may not ba contorted. Become like jelly .

The rocks which constitute the earth's onist are divided according to their ralatiTe portion and foml oDDtenta as in the foUowing table ; thosa at the top of the table being the youngest. Port Tertiary— Hscent and Pleistocene.

Sasin-sbaped bendinpi of te artJi'a cmat, tba

reveres of antleluuli. An arsenide of uiokeL Intermittent boiling springs. Depofuta formed by the Im iheeta of the glacial

period. Depoaila formed by existing glaoieim or their

former extensions. Sulphate of soda. A variety of cobaltine. A stratified granitoid nek in which the minerals

ate anuiged in layers. A hydroDs oxide of iron. A netalhc element. Sulphate of sno.

D,g,l,.9cbyGOOglC

Gbahttb, Orahdlab, .

Oufbitb,

Obubkn,

QaST COITKB,

Obossulau, Qtpsdu, hxhatitb, . Hau/jtsitx, . Hakoihh Wau, .

Habmotoub, Haubiutb,

HAUBNANNm HUTNB,

Hl&OINTH, HlDBAULIO Elevatob, .

Htdbooabsonb, Htsboiuohesitb, Htdbotbkkhal, .

loELAMD Spas, . Idoorabb,

Itunoirs, ,

. Hfdistedperoiiiifl of iron often quaitzose, found capping lodei Hat conttuD femiginoai mmeiak. . An igneom rock, see p. 6- . Id the form of gnoa. A form of carbon.

A gnuiitic rock conauting of mica and quartz. . Tetraliedrite ; a complex copper ore; see p. 163. , A greeu variety of garnet. . Hydrous mlphate of lime. . AnlijdrouB oiide otiion. A bard clay.

The upper aide or boondtuy of a loda oppoaitv the foot waU. . Eydroua ailicale of almnina and baryta. . Solphide of manganese. . Anbydivua oiide of manganese. . Klieate of alumina, loda, and lime, and anlphate

. An apparent lateral displacement of a lode prodooed

by a fault. . Black variety of augite. . Bloodstone ; a dark een variety of quartz nith

Bpecka or veina of jaepar. . Tellnride of gold.

Hydrous ailicate of alumina and lime ; a leolite.

Of the same structure throaghout

A silicate of lime, magnaiia, and iron.

An igneoUB rock ; nee p. S.

Chloride of silver.

Warm and moist. , A variety of Eircon.

A machine for raising gravel by means of hydraulic prasaura.

Lime which has the property of letting under

Compoundi of carbon and hydrogen, . Eydrona carbonate of magnesia. Pertaining to hot water, eapeaaUy with respect

to ita aotaon in diasolTing, re-depodting and

otherwise producing mineral dumgea within

the cmat tn the globe. . Containing water regarded as water of crystal- Haation. A ulicata of magnesia and iron. A rock formed of labradorite Hid hypeisthene. Cryatalliaed transparent carbonate of lime. A silicate of alumina, lime,' and magnesia. Applied to all agencies, operaUoos, and results

which appear to be connected with snbter.

ranean heat.

iMKHnmiHa TAiLnoa,. Ikprbohation, Ikdkutob Vbk, .

Iir ,

Ibidiuv,

IXON Ftbtibs, Ibomobfhish,

Olobsabt. 225

Enclodcg: tham so that thej cannot flow when

they ars not wanted. Ore dlssetniDated tfarangh rack and having no

haiplj-defined limits. A vein which ia not metaUifBTom itself, hnt, U

followed, leadi to ore depodts. Haidened. A riliceotu deposit fomied cihieflr of fragmeote

of diatom*. In the place where found. Interbedded with.

Swelling when heated.

Iodide of silver.

A metallic element.

EUhiUtdug a play of different colony like s rainbow.

A metallic element . An allo7 of iiidimn and oeminm.

A metallic element. . Snbide of ir

I forme, of repladng c minerale. A flexible sandstone.

Nephrite ; a eilicate of lime, magneua, and iron.

A snlphide of lead aikd antimony.

A variety of drcon.

A haid variety of ooal, which ii cut and polished

A very pure clay.

A giun which emdee from the Icanri pine in New

Zealand, and ie frequently found f cssiliBed. Chloride of silver.

Cly slate.

Those rocQcs in which lodes become productive

of mineral of value. See Cyanite.

A silicate of lime, alumina, and soda. Lenticular sheets of eruptive rock spread between

beds, having an intnudve origin aitd not occur'

ring as an overflow.

S2e

hAMVM, IlAPIB LAIULI, LAUHOHTin,.

Luduo,

Lbpidoltii, . Lbkooutb,.

Liomn,

Lmosuran Brom, Lira BiTXBB,

LODB ToBiuncnt,

Maohbia, .

Maoiibuis, . MABsmo Ptkimb,

Maonxtitk, 4 IlAiN Bonoic, MALAOsrni, .

Harqahh . iiAnaaoTM, .

Mabtiti

Melaoonitk, Melaxiz .

MgT.ap titw ,

Qlossabt.

Id thin ibeeta.

Thin pUt8 or scale*.

UltnuDarins, lee p. 77.

A silicate of lime and alamiua.

Book* which have flowed in a molten state fron

The auriferoni portion of allnvial depoaita

marking the former cooiM of the rtceam. Iisni'like. . A lithis mioa. A TBiistj of pTToicma-oliTine-rocfc. Fhotphate of copper. A hrdroos variety of ooal ntaining it woody

Book fomwd of carbonate of lime,

Hydroiu oiide of iron.

A inlphide of niokel and oobalt.

A vary fine grained limeitone.

Biven which are now running.

Any vein that appears likely to prodoc

Si

Ulea

Parte or gronudvork of igniraui looka. . Oxide of magnesium.

Carbonate of magneiia,

Pyirhotina ; a sulphide of iron. , Magnetic oxide of iron. . Hud rock below allnvial depont*.

Oreen carbonate of copper. , Capable of being moulded.

In smooth, rounded piominencea.

A metalLc element.

Hydrous oxide of manganeae.

Metamorphic limeatone.

Radiated itea ; rhomMo sulphide of ircn.

A variety of luunatjte. . The rook or mineral contuning metallio ota

A hydrous silicate of : Black oxide of copper. A black variety of gamet. An igneous rock. A metallio element.

D,g,l,.9cbyGOOglC

Glossary.

1£btbobio Iron, MioAa, . ,

NATBOirra, .

Natsoh,

Obbidian, . Ootabsdbite, Ootahxdboit,

. Metal bearing.

. A term used to eiprms A ohan in the miSeralogical or chemical oompoaition Aud intemAl structure of rooks prodoced by the 6perAdon of heat, heated water or vaponr, presEtire, &c. Iron which has faUen on the earth from intor piaaetarj space. . Flexible uid elastic minerala oocnning in thin platee ; ailicatea of almnina and potMh, magnesia, lithia, or iron. , A metamorphic rode coniiiting of a lamutated

aggreitate of quartz and nioa. . Sulphide of nickel. . Araeniate of lead, . Red lead ; oxide of lead. . See Oeeltjf/ical TaUe.

Sulphide and arsenide of iron. . Sulphide of molybdenum.

A metallic element , Molybden-oobre ) oxide of molybdenum. . A variety of adnlaria felapar. Deposits formed by gladers. Impure asbestos. Pyrites ; sulphide of inm. . Potash mica.

Telloiide of gold and lead.

Hydrous silicate of alumina and loda ; i , Caibouate of soda.

Jade ; a silicate of lime, mogneBiA, and ir

Those who ascribe all geological the action of water.

A metolljo elsmant.

Argenida Of nickel, . An aneniate of nickeL

Sulphide of niiJcel and iron.

Compounds of nitric add with baacs.

Nitrate of soda.

CoQcreldonB of rock matter aggregated round A central nucleus.

Silicate of nickeL

A body about which anytlling is oolleoted.

A Tolcanio ASi.

Titanic oxide.

An eight-sided figure, each of the idea ad

Oboanio Ookfodndb, . Obohtal AuerHTCT, .

TOPAl,. OSPDOHT, . OBTHOOLAa

Odtobof,

0X0*3, .

Pan AKAUiAKATioir,

PiBOLTnO Obu, .

Fl.AQlMn.ABa,

Ol063Ast.

BiRfte of aloiniiuk toda And Ume; soda-Iims

febpu. . SilioBte of nugDMu Mtd iron. A Tuiet; of qiurta in aUm*(a en of wfaita

and brown or vhit and bUck. Hydrooi nlic Exhibiting ft play of colony like the preciona

opaL Componndi contAining urban, gsDenUj' deriTed

A. mdphide of Maenic

AailioKtoolBlntniiia*adpotaali; poUsh f elspai- The Appeaiuice on Che muface of the ground

of ft rock, lode, or coal Beam. Oonpoanda of oxygen with any elemeol Mineral wai ; a loUd petrolenm.

WaHa built of loose nutteiiftl in mines to anppoct

the roof. A mstaUic elemenL

n of niTer or gold with meroury by

. Sniall bftDdi o( ahale or stone oocmring in a coal

Copper pyiitea whit has taminhed.

Besembling mother of peari.

Tdni of ooanely cryitaniied gianite in gnmita.

A variety of ohlorite.

A Tolcaoic glasB. , See Geoleffkal TaHe. . Changed to atone.

A natural mineral oiL

The Btudy of rocki. . Telloride of ailvac Aud gdd.

A delicate of glnciaB ; a gem.

Compounda of phoephinic acid with a base.

An elongated body of ore in iimaatone, generaUy standing nearly verticaL

In concretuHis about the eize of a pea.

Oxide of nnniam.

A Toloanic glass, eee p. 9,

Felspan in which the two principal clearag planes are not at right anglia to one another.

A green Tarietf of quartz.

Easily moulded.

, An uiej at piatmimi ana inaiam. . A metallic elMnent.

. A vwiety ot epinel.

Pucationb, .

Puooras, . .

. Bee Table.

Plukbaoo, ,

. Graphito ; ctvbon.

PLDifB Bob, .

. Those who attempt to explain all geological

. , A Bnlphide of rilver, ooppw, snlimony, ud

Kaolin, the forest form ot clay.

Fokfhtriti,.

. An igneooB look oondating siHntianr of a tnie

Position Bloom,

, M'"iiB iaimB which aie in a london which

will contain a lode if it oontinne, in the dine-tion

in which it hw been proved in other claims.

Fotabh,

. Oxide of potuuiun.

by the addition ot another lolatdon.

. A rilioate of alumina and lime.

. Inprira.

. Solids whoee boAea are plane figwei, and whoM

Pboddottvi, .

. Yielding payable ore.

Pbofilue, .

. OriginallT defined u tertiary vdcanio rocks

a fine-grained non-vitreoiu ground maa*.

. Searching for minerals.

. A ffiilphide and of nlrer.

. ManganaU of baryta.

, A vedcniar volcanic glam.

PtTBTLxoF G&Bnm,

Ptsabotbit

. Cubic sulphide of iron.

, Phosphate of lead.

Ptbopi, . .

. A variety of gamat.

. Magnetic pyrites ; sulphide of irofl.

Qdabbizd, ,

. Worked in the open.

. Cryitallised silica.

D,g,l,.9cbyGOOglC

Bed Lead, . Redbutuite, RBDVtmoH, . BEsn, . BBnuonoR,

RHOHBOHEDBOIt,

Bhtoute, Ribbon Vbiks, Rim Book,

Book OBniftL, Rook Savt, . Boor, .

Rubkwjte, .

Sai-Ahhokiao, Saltpetre, .

Samflino, .

Olob8Abt.

. An igDMmi lovk, we p. 0.

A metunoniic undstone.

An igneous rock, (ee p. 9. . Oxide oalciDlD produced by routing limestmia.

MercDT7 ; a metAllic element.

DiTeifing from centre. Branched In many direction!. Sulphide of anenic . MlninDl ; oxide of leal . OoppF gbnca ; aulphidaot copper. , Bedacing compound to a metallic iitata.

Lodes, ledge, or Teini. . DeTiation from a direct conne ; the property poseBed by some taineraU of deflecting ravi of light. . Difflcnlt to treat for the leoovny of metals. . Kidney-liks. Reumbliog renn.

Ymtu travendng rodu In all direotiouL . Faolti doe to thnut, the banging vail aide of the

fault beii forced apwardi oa the footwalL . Silicate of maogMieae. . A twelve-sided figure, eeh idde of vbich Ei

rhomb. . A dx-dded figure, each nde of which ii a diomh, . An igneom rook, eee 9. . SetBandtd Veint. . Bedrock in aUaTial mining which onterope ainve

the level at wdiich the anTiferooi lead occnre. , A Twiety of ohlorite. , That portion of a bed or ooal eaic which lies

aboTe a level U eaid to be " to the riie." . A clear colooriem variety of quarti. . Chloride of aodimo.

. The strata immediately above a coal uam. . A red Tariety of tourmaline. /

A form of oxide of titaninm.

. Quartz reefs occurring in the form of saddles;

see p. 141. . Chloride of animoninm. . Nitrate of potash. , Mixing ores bo that a portion takett may fairly

represent the whole iKidy. . Consolidated Band.

Olosbakt. 231

Baraas,

Sabdontx, .

A variety of quartz.

A group of reptiles now cxtinot.

Soabp,

A ateep face.

TnngBWte of Iini.

Schist,

Schobi,

A black Tarifltj of tourmaline.

Skotili, , . .

Oaa be cut with a knife.

Ssotiok,

A cut tbroDfcli.

Bedimknt, .

A dBpoLt formed by water.

Asgnatlons of ores in a cavitjr baring mi

uregular form but defined linut&

An element.

Hydrous eilicate of magnsda.

Sbau,

BHDiau,

C9ean gravel

Depoeila of ore in lodn, which have a limited

depth i they generally dip at varying anglea

Oarbonata of iron.

An oxide of silicon.

Comporaids of siUca or iilidc add with a baM.

See atolOffKol TabU.

A metallic element.

SiLTXR Olako .

A deposit from hot spritigB.

Suoa,

Furible nlicates formed when ores are smelted

and the metali eitraoted.

Smooth, poliahed, and sometime striated sor-face

on the walls of lodes produced by frictioa.

Blidi,

A fault or cross comie.

Suna,

The very fine gramed particUs Idnced by crashing ores, which do not readily sink in

water.

BaSIMS COAHNEL,

the gold has been erttacted from aUuvial beds.

Sldiob Box, .

A wooden trough in which aUuvial beds are

waabed for the recovery of gold or tinstone.

SLUiauia Tabls, .

A Uble on wheek used for washing black sand

for gold on the coast of New Zealand.

Shaltihi, .

Aisenide of cobalt.

Bwrmoinn,

. A compact variety of talc.

BODi

Spatbio Ibon,

Spibm,

STAUomm, . .

Stauquitb,

.Stamnih*, . . . .

Stepbahitb, . . I

Stkatutoattoh, .

Stbiei,

STBOMBIEWSt, .

Stbobwa,

Stbontidm

8in,PHATES

Solpbidm

,

Svnstone,

Sdbtaoi CHAxan,

Stebitb,

Tachylttk,

Tailinob,

Tail Back,

Talc,

Tbllubicm,

Olosbabt.

Oiide of sodium.

The final Btage of volewiio enipttaii when rteun

and gwwH only are emitted from the onttecs. Carbonate of iron.

Alnminate of magneeia.

Tincle-like iTicrustationa At> down fnroi

the roof rf caveB, ffimilar to Btalactiteo, but formed on the Boor

of the eavee by the deposition of solid matter

held in solution by dropiriiig water. Sulphide of tin and copper. Hydrous Bilicate of miffneaia. Sulphide and antimonide of . Sulphide of diver and iron. Sulphide of antimony. Hydrous silicate of alnminA and lime. Bock which is traveiBed by so many metalH-

feroui veine as to radar the whole deposit uf

Hnfficiant value for trtment. The arrangement of sedimentary rocks in beda or

The powder of a mineral or tiie colonr-Effeot produced by scratching it with a knife.

Marked with fnrrowB.

A horizontal line upon the floor of a bed or foot>

wall of a lode- Sulphide of silver and copper.

Oxide of strontiuin.

Carbonate of strontia.

An element.

Compouods of giilpbnric acid with a baaa.

Compoondg of aolphnr with metals.

An element.

A sulphide at hydrogen.

A variety of oligoclase,

eipenses incurred on the surfitce of a mine which have to be charged agunst the mineraL

Tellnride of gold and trilver.

Strata bent in the form of a tnragfa.

A volcanic glass.

The refuse from a mine after the valuable or*

have been extracted. A channel for removing tulings A bydrona silicate of magnesia. A metallic element.

Till, Tiiuzm,

TiK DiBH. . TiK FniTBB,

Xtz Tra,

Top&amp;E, . Tokbakhs, .

Toimuun, Traohtti, Tbanblccbnt, Tbahsiarbht,

Trappban, .

Trbmouts, . Triasbio, TBioLnno, ,

Tbidtmiib, .

Tripoli,

Tboublm, .

TrMQBTATIS, TOSQSTEB, .

ULTBAHABim,

Undbbolat, . Unbeblai, . TTbanidm,

A mlpbidc and ansnide of copper ud kon.

A complsi copper ore, lee p. 163.

HydrouB silicate of olnmina, lime, uid lodk;

A glacial depodt Hornblende andesiie.

Snlphide of copper and tin. Cassiteiite; oxide of tin. Oompoimds of titAuic acid with a hue. Specolar iron conttdning oxide of A metallic element.

parldoles

lighter colonr. A silicate of alumina with fluorine ; a gem, A dark brown variety of cannel coaL A ailioaCe of alnmina and other oxide*, see p. An igneona rock, see p. d. Transmitting light, bnt not (xamipBrent. Tranamitting light perfectly; object CMi be seen

through a trKogpareDt medium. Bocks occurring in dyke and (beets. . Material deposited by calcareuu* spring*- . A white Tariety of hornblende. . See OeoUgkia Taile.

Crystak bftving three axes which are not at right

Disturbances in a coal seam. Compounds of tungatic add with a base. . A metallic element.

Lapis lazoli, see p. 77.

The clay forming the floor of many cod M

The inclination of lodes to the verticiL

A metallic element. A chrome garnet

Oxide of antimony. A silicate of alnmina, lime, and Glassy.

Hydrous phosphate of iron. , Ejected from a Joloano.

WlTHBRin, . WOLTRAH, .

wollutontt Wood Tih, .

Zno, ,

ZiNo Blook, Znom, ZiHOEmn 1

ZwirrmR Rook, .

Qlos8Abt,

An impure eartbr oi , Prti of ooal MMM which have been ranoTcd bj

Btreanu flowing at the Uma of their tormatioii. . The powar which ii dereloped hy the praaora of

rater when applied to water wh " '" — —

&c.

Anfajdcooa kiliote of lina Danu boilt from the nde of a i

abject of defleotii tt from its coune. . Oarbonate of baryta. Tnngatate of iron and manganeea. A ailicate of lime. Tiiwtone of a brown colonr of rarioiu shades ;

botryoidal and renif onn in ahape and Sbrotu in

If with the

Molybdate of lead.

. Hydroua nlioatee of alluUei or alkiliite e with nlicatea of alumina.

A metallic element . Sulphide of zino.

HTdroua carbonate of lino.

Red oxide of zino.

Sulphide of lead and antimony.

A ailicate of sroonia ; a gem.

A non-fenif ennu rhombio ally of epidota.

A atoclcwork poiphyty at Altenberg.

n,g,t,7.cbyGOOglC

Index.

Ade1oDa,9iL Agate, 86,76,79. AUbtuidine, 191. Albtte, 60, 62. Albnmia mine, 95. AIIdtuI dspoaits— Their mode of ocenrreaw, 4, 120; source of materials,

Amber, 198, 204. Amethyit quartz, 7G, 78, 79.

AndiJndte, 77, 79. Auelesite, 154. AiiEydrite, 50. 52. Annmbete, 189. Anortliite, 60. 63. Aathiadte, 198. Antimony, 193, 191 Apatite, SO, 33, 78. Apophyllite, 86. Aragonite, 49, BO. Argentite. 149, 1501 ArBenic, 193, 194. Asbestos, 63. Aaphaltnm, 198. Atacunite, 164. Angite, 60, 64.

„ aiidesite, 9. Australian meEs, 12fl. AzDiite, 164, 168.

BiBXR bedi, 88. BHTtcn, GO, B3. BaTTtooalcite, OOl BMalt,9. Bwyl, 72, 78, m

BioKte, 57. 69. Bismuth, 193, 195.

., dire, 197. Binautbine, 197, Bimnnthite, 197. Bloodstone, 75, 79. Blowpipe— Oharaotera ol

BaKaak,20L

Boramte, 78. 79.

Borax banda— Colour of. 3b ; with colalt. 36; with copper, 36; with titanatee imd tongetates, 36 ; with manganese, 36 ; with niokel, 36 ; with chromium, 37 ; with unniDm, 37 ; withir "

BiiiEit, 60, 65. Brooldte, 177. Brown coal. 198.

CimseoBK, 76, 78, 79: Calamine, 180. Calaverite, 147. Calcdte, 49, 60. Cannel oosl, 198, 199. 30L Carbonate of lead, 1S6.

„ of soda, and nitre — Tests with, 38. Carbonic acid— Action of, 91. Camelian, 75, 79. Gassiterite, in. 174, 175. 177. Cat's eye, 76, 79. Cave depouts, 113. Celeatine, SO, 63. OeroHite, 154. Corvantite, 196. Chabaziie, 66, 67. Ohalcantliite, 164

Chdcedonv, 65, 76, 79. Chalcopynte, 163, 167. CturcoBl — TmM od, 37 ; with corboiiate

Chloanthite, if. Chlorite, 57, 58. Cbrome iron, 192. Chmmite, 192: Chromium, 179, 192. Chryobryl, 71, 78, 79; ChTfKICollA, 164.

Chrysolite, 76, 79.

ChroDTMO, 7S, 79.

Gincsbar, 1A8, lfi9. 162.

Citrine quftitz, 75, 79.

Cleavsge of mineral*, 17.

Cool, 193, 199; origin of, 80; occurrence

and prospectiDK for, 81 ; comparative

of. 84 ; bands in, 84. Cobalt, 179, 187. CoboltiferouB mispiclcel, 1S9. Cobaltif erona wad, 189. Cobaltine, 189.

Colonr of mineTBlB, 20 ; table of, 25. Combustible minerals, 198. Uomstock lode, 92, 95. Cautact depoiiti, Ill- Copper, 162, 163 ; m BtratiSed deposits,

85; arsenides ol 1""

of, 168. Copper glance, 163.

Covelltte, 163. Orocidolite, 79. Crocoisite, 154. Cryolite, 50, 54. Cuprite, 164, 16&

Detebuihation of mioerals, 39

IHallage, 60, 64. Diallogite, 191, Diamond, 68, 78, 7% 1991 Dichroite, 73. Diopside, 60. 64. Iho|>tase, 164.

Dolerite, 9. Dolomite, 50, 52. DTnamicB of lodee, 114.

Enstatite. 64, 65. Epidotfl, 77, 79. Etubescite, 161 Erythrine, 169.

Fahlbkds, 107. False topaz, 75.

Faulting of lodea, 114; relative age of,

of, 166; black oxide

Elabtioity of minerals, M Elaterite, 198. 203. Electnun, 146. Embolite, 149. Emerald, 72, 78, 71 Emer, 7L

Flame— Oxidising and fuaiag, 34( redu-iicg, 34; oo&ur of, 3Si red, 36; yellow, 36; green, 36; blue, 36;

violet, .% FlatB, 110,

Flexibility of minerals, 26. Floors, 109. Fluorspar, 60, B4. Fuller's earth, 68. Fusibility of minerals, 35 ; scale of, 3S>

Galmei, 130.

Garnet, 73, 78, 79.

Garnierite, 189.

Gosh veins, 101

Geolccal— Age of coal, 2 ; age of go!4 3 ; notes in the field, 11.

Gersdorfflte, 189.

Glass tubes— Tests with, 39.

Glancodote, 189.

Qffithite, 182, 184.

Gold, 146; in stratified deposits, 86; listribution, 136 ; mods of detection, 136 ; asBodation with siiIpMdes, 136 ; auriferous belts, 137 ; in erupldye rocks, 137 ; in bedded veins, 138 ; in reefs traveraiiig sedimentarv beds, 139 ; in reefs associated with dlorite, 139; in shoots, 139 ; in saddle reefs, 141 ; in flat veins, 141 ; in itacolomite, 142; in timarite, 142; in Transylvania, 142; in Nevada, 142; in lodes, 142; at Mt. Morgan, 143; in deep leads, 144,

Onto its, e. Graphite, 19S. Grey oopper, IBS, 167. GiilgaDBgoldlield,99. Gypmim, GO, 62, SS.

H

EABDKEsaof iniDeralB,34; scale of, 24.

Harmotome, 66.

Haaerite, 191.

B8iDaiiiute, 19L

Hauyne, 79.

Hamatite, 1S2, 1S4.

HeaveB— Law regulating directioa of,

Hedeobenite, 60, 61

Heliotrope, 76, 79. Eeulandite, 66. EorableDde, 60.

„ aodeaite, 9.

Horn silver, 10. 151. HydromagDeute, SO, 63. Hypertthene, 60. 65.

loiEAHli apar, 49.

Imrrfaatioas. 106.

lotbrgyHte, 149, 15L

Iridosmioe, 146.

Iron, 179; enlpbate of. 134 ; oteB,inodc

Iron'

Iron . Irregnlar c

Eaolih, 67. Kerorgyrite, 149, ISI. Kyanfie, 77, 79.

bimony oi ee, 1S6.

Lead oree, 154.

Leadville, 94 Lotrarerz, 161. Leaticular aegregationa, 108.

Lepidolita, 67, 69. Libetheaite, 164. Ijgnite, 198. Limeatone, 51. Limonite, 182, 134. Lion site, 169. Lithographic Btone, 61. Lodes, 99.

Magnetiu pyrites, 186

Masnetite, 18.% 184.

Malachite, 164, 163.

MUeability of mineraU, 26.

Manganese, 179, 190.

Mangaaite, 191.

Marble, 51.

Maroaiite, 185, 187.

Meersobaum, 56, 67.

Melaconite, 164.

Mercury, 158, 159, 162.

Meteoric iron, 184-

Mica, 57, 58, 69. ,, preaenoe of, in rock, 95.

Mtcrocosmic aalt— Colours of beads,

Millerite, 189.

Uimetite, 161

Mineral deposits — Their mode of occurrence, 3 ; conditions to be studied, 6 ; theories of origin, 90.

Minerals with metallic lustre — Easily fusible or volatile, 41 infusible or fusible witli more difficulty than irthoolaee, not volatile, 43.

Mineral veins andlodei, 89; frecturiag

of rocks, 96 ; distribution of ore in,

100; how filled, 91. Minium, 194. Miapiokel, 18 187. Molybdenite, 177, I7a Molybden-oohre (Molybdite), 177. Molybdeoum, 171, 177, 173. Mountain leather, 63. Mount Morgan, 96, Muscovite, 67, 50.

NAaiAoin, U7.

Natrolite, 66.

Nephrite, S3-

Nieopyrite, 189.

Nitrate of ooUlt-Terta with, 3

Noble metal, 136.

Obbisuk, 9; Ootfthedrile, 177. Olisoolam, SO, 62, 76, 79.

Olirine, 76, 78, 79. Onyx, 75, 79. Opal, B6, 78, 78, 79. Oriental EiinethvBt, 70. 78. emerald, 70, 78. ,, topai, 70, 7S. Orinjnent, 1S3, 191 OrtbixJue, W, 61, 76, 78,79. Oiokerite, 198, 203.

Paludtdm, 146. Peacoclc ore, 165. Pennine, 68. Perlite, 9.

PetmUum. 196, 202. Fetzite, 147. Phenakite, 73, 78, 73. Pitch blends, 192. Fitclutoae, 9. Plasma, 75, 79. Flatiniridium, Hi, PJatdnam, 14S, 146. Plombaso. 199. Folvbaute, Piehnite, 66. PnnuUte, 149, ISO. Psilomelane, 191. Pmnice, 9. Pyiwrgyiite, 149, 160. IToInaite 191. Fyromorplute, 164, 16S. Frrtiotiiie, 187.

Rbalsab, 193, 194.

Red lead, 151

Redruthite, 163.

Retjcolated reins, lOS.

Rhodonite, 191.

Rbyolite, 9.

Bipidolite, 68.

Rook oryrtal, 74.

Rockg, 7; igneous or erupve, 8 ; hydiothermal, 8; tnppean, S; table of eruptive rocka, 9; voloaoic 10 ; >edimentary, 10 ; movementa of. 10 ; strik* and dip, 12; fracturine of, 96.

Rook Bait— Occurrence <rt, 85.

Rnby, 70, 78, 79.

ButUe, 177i

Satdonyi, 78,79.

Bchmidt'e law, 119 ; exeeptioiii to, 12S:

Scbeelile, 177, 17H.

Segregated veing. 111.

SOTpentine, 57, 68.

8hoot>,m

Silver ores— Valuing, 152.

Smsltine, 189.

Smell of minerals, 27-

3moky quartz, 76.

Soapstone, 66.

Soluble uita, 48.

Spedfic gravity of miaerala, 27 ; high

demdty Uqaios, 29 ; diSonoQ column,

Spinel, 72, 78, 79. Stahlerz, 16L Staimino, 16.1, 177. Steatite, 56, 67. Stephaoite, 149, ISa Sternbecnte, 149, 8ldImite,I96.

metallic Imptgnatioiu, 85 ; gold in Transvaal, 86 ; gold in New South Wales, 87 ; workmg eipenaai, 88.

Streak of minerals, 24; table of, 2S.

Stromeyerine 149, ISft

15 ; Kaoobaroid. 15 ; lame oapilluy, 16; obrooa, IS; rooiau

16 1 baoilluy, 16 ; dsndritic, 16 conoretiunaiy, 16 ; niBminJUjuy, 17 botryoidal, 17 ; reniform, 17 ; vit reoiu, 17 : luiioiphous, IT.

Stapbnr, m, 1.

SnlphiiTetted hydrogen — Action of, 81.

Syenite, 9.

T.

Taste of minerftk, 27. TellnriDiii, 147. Tennantite, 163. Tetrahediite, 163. Tlutmes eoldfield, 92. Thomwnute, 66. TiD, 171, 177. Tinstone, 171. Titanic iron, 183, 184. Titaninm, 171, 176, 177. Topai, 72, 78, 79. Torbanite, 198, Tourmaline, 74, 78, 79. Trachyte. 9. Transvaal depodta, 66. Tremolite, 60, 63. Tridymite, 66. Tronm, 48.

Tungsten, 171, 177, 178. TurquoiEe,77, 78,79.

Valentinite, 195l VeBavianite, 77, 79. ViTianite, 184.

WiUemite, 18a

Witherite, 50, 63. Wolfram, 177, 17 WollMtonite, 60, 65. Working expemu, 88.

Ybllow jacket, 100.

Zeolites, 65. Ziegelsrz. 161. Zinc, 179. Zincblendr, ISO; Zinc bloom, ISL Zincite, 180. Ziroon, 73, 78. Tfr

,

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(LONDON : CHARLES QRIFFIN A CO.. LIMITED. EXETER STREET. STRANft

tiremMBBiNO and xmobasiob.

IN, Thartugkty Revised and Enlarged. With W-uiaermts JUustnUitms. Handsome CUlh. gfi

Hydraulic Power

Hydraulic Machinery.

HENRY ROBINSON, M. Inst, C,E„ F,G.S.,

C M T — Ta — Dlscbarn tbroueh Oritice*, — Flow of Water through Kpo. — Ac[:iunulaton.

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THE PIinCIPLES UD COISTRUCHOI OF

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WHk Pnotiokl lUnatmtiiMia of Eiiams *nd Pumps to Misixs,

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tT HENKT

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atal Spg, NbiAmm CM*. WWi mMWRHw llliatratlimi iai4 TalUM. 28t.

The Stability Op Ships.

Sir Edward J. Reed, K.C.B., F.R.S., M.P.,

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THB SESION AND OONSTBTTOTZON OF SHIPS. B; John Harvard Biles, M.Inst.N.A., Professor of Naval Architectare m the Univeisitp of Glasgow. [/x Preparation,

STEEL SHIPSs

THEIB OOirSTBUOTION AHD UAHTTEHTAKCB.

4 Manual for Shlpbulldert, Ship Superintendents, Students,

and Marine Engineers.

By THOMAS WALTON, Naval Architect,

COHTENTB.— I. MBHofactnre of Cast Iran, Wroaght Iron, knd Steel.— Composition of Iron aod Steel, quality. Strength, Tests, ftc II. CUssifloation ol ateel Ships, til. OonaiderBtionB in mulring choice of IMre of VeaKl. — Framine of Ships. IV. Strains experienced by — Methods of Computinf and Coropariiig Strengths of Ships. V. Oonstruotion of Ships. Alternative Uodes of Oonstruotion,— Types m Vessels. Turret, Self Trimioing, and Trunk SteameiH, fto.— Rivets and Rivettiog, Workmanaliip. Vt Pomping Arrangements. VII, Uamtenance. — Freventdoit of DetetioiatioD in Uie Hulls of Ships. — Cement, Paint, fto.— Indbi.

'SolhoroniED i.cd wall wrltlen Ig eiecj eh4pter In Ibe baokltastitiidtnaalttoialael anTotlbein u wonbj or eioaptloniil praiis. AltOEettaer, Iha work Is aiBaLlant. mid will prove ol Bteat vslne thoae for whom it ia inianded?— TV BmrtiMw.

At PBBaa. In Handsome CJoth. Very fully Illnatrated.

Present-Day Shipbuilding.

For Shipyard Students, Ships' Officers, and Engineers.

Bv THOS. WALTON,

Anthor of "Know Tour Own Ship."

OBHaaiLCoHTKNT'a.—CUBsification.— Materials used in Shipbuilding. —

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Bditbb bt BDW. BLACKMORB,

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tarFairpla. "A vsai DBsnTL SIMIB."— ffotton, Ira tba whole Befusi u a REraKEKoa Librakt. Hun-

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to tlw Uwatunt Marina. The ia ptgei ol thla book an the moot Vli.n<

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>nometFy : For the Young SftUor, Aa By RiCB. C. BiPOK, of the

"a. m""'*' CoUbbb, B.H.H. Woroaeter." THfflD EWHOH, JlavtMd. ellabla volume."— ScAtwimotMr.

Ppactioal AlMbra. By Rich. G. Buok. Companion Volume to the

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luuile

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GRIgglN'S NAUTICAL SERIES .

Introductory/ Volume. Price Ss. 6d.

British Mercantile Marine.

Bt EDWARD BLACKMORE,

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d ImmuonTB . , . may be read itith rmom aiiil nrjom."-

'Btut miata of tba labjsn la dealt with In a war whtoh ihom Uiat tti lowi the rope' ramllUrlT."— ftolmtan. "Tbl( ADHUAiLa . . . tm irllh luefiil iDFormatlon— Shoill b

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The Tolume oontaiDS tHe ii bulb or Tm sota

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Navigation:

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Marine Meteorology,

FOB OFFICERS OF THE MEBOBANT NATY. By WILLIAM ALLINGHAM,

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flea I-Booka.— AlmoipIierlD Preisore.— Air Temperslimn.— Sea lemparatnrti.—

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Practical Mechanics:

Applied to the Beguirements of the Sailor, Bt THOS. MACKENZIE,

MiUr Mariitr.-P.SJ. Gnnux CotmHm. — Betolation and CompoBitdon of Forcea — Work done by MMhinM and Living Agents — The Mechanical Foweni : The Lever ; Knricki ai Bent Levers— The Wheel and Axle : Windlaa ; Ship'i Oaprtan ;. Grab Winch— Tacklfls : the "Old Man"— The Inolined Flane; the Strew— nie Centre of Gravity of Ship and Cargo — Relatin> StMugth of Bope : Steal mr Manilla, Hemp, CoiiDenic and Shean- CalmUUim cl Ui OowlmakinK Strain of Fii Spar— Csntre of Effort of Saila— Hrdnrtatda: tlie Diving-bell ; Stability of Floating Bodies ; the Ship's , &a

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BJiipitg World.

No Sbips' OmoiBs' booxoabs will hsnoeforth be oomnlete without OAiruiT MAOKUim'B ' Fbaotioal Meohakioh.' Notwithstanding mj nuny ITMn* ipienoe kt ea, it has told me hom mucA more there u to acuirt."— (Letter to the Pnblishen from a Master Mariner).

" I most aiprea my thanks to yoa for the labour and oaie yon have talceo In 'Praottcal Mbohahios.' . . . It la a uri's bxpbbuiiok . . .

What BO amount we frequently see wasted by rigging pnrahases without reason and accidenta to spars, *c., *o, ! ' Practical Mbckabiob ' woiiiJ> bati all THUL" — (Letter to the Anthor from another Master Mariner).

A Manual of Trigonometry:

With Diagrama, Examples, and Exercises. Price 3s. Od.

Mr. Bnok Text-Book has been speoiallt fbbfarbd with a vtaw to tUB New Examinations of the Board of Trade, in which Trigonometry is HI obligatory object.

A Manual of Algebra.

Designed meet the Hequirements of Sailori and otiert. iJEcoNi) Edition, Revised. Frioe 3h. 6d. ThBS atemenlary norfes on iLaiBKt and TBiaoHOHnsT us wrltum apedallj top Itassa who will bsTs Kttte opponsnit; of aoDsaliiDt: Teuber. They ua books tor "sm j-

tte Kisreissa ua Elven. An; demon msy rudllV. bj otrefDl itodi. beooma msstar ol their sonlents, end Ihoa Isy tlie fouDdstlsn for ttunhsr msUuinstlul soBras, U deatced. It la ksiied tbat to iha joiuiger Offlaan ot our Harcantlls Ksilne lti will be toimd dsoldsdlr BlasaUe. The BismplaB ud EisroiBSa trs lafeaDfroin Iha unlnatioa Papsn let lor the OsdsIB ot Iha " Worceiler.'

rransHl. snd wall got op. ... A BrM-rMe Elemeatary — itaaueal Mafftift. '.'For flomplwe Llit o( 'j WJOTIO*!, BsMB. see o.

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Naotioal Works. 43

GBIFriW'8 NAUTICAL SEHIES.

Sbcohd Edition, Tboronghly Revised and Bitended. In Crown Sto, H&ndMime Cloth. Price 4e. Od.

The Legal Dotes Of Shipmasters.

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Latitude and Longitude:

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Bt W. J. MILLAR. C.E.,

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it HANct and USKFDL, soTFLa and oliab."—

First Aid At Sea.

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Know Your Own Ship.

By THOMAS WALTON, Naval Aechitbot. Speeially arranged to suit the requiremenU of Shipa' Offioera, Shipowmtra, Suoerintendenta, Draughtamen, Engineera, and Othara, COnTBRTB, — DliplaconiBnt nd Deadwalght. — McaaenU- — Buoyincr. — HnM. — Stnictiire.—BtabllllT. — — B.llutliig. — Loading.— Shitting CirgoH.— laNl at AdmliiloD oT WBter Into Ship.— Trim Tonniwe.— Freeboard (Lond-irne).— CiliiaWiaH.— Set of CaloolaUoiu troDX Actual Imdix.

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Steel SUps: Their GonstiactioD and Haiitenaiice.

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Ubkibal Contents. — Pabt I, — Principles of Marine 'aUion. Pa&t II. — PriDciples of Steun }<:neermg. Part III.— Detailt of Marine Enginaa ; Design and CalculatioDs for Cylinders, Piatoni, Valros, EzpansioQ Valvea, &o. Part IV.— Propellers, Past V. — Beilen. Fabt VI. — MiscelUneoua.

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THE ELEMENTS OF CHEHICAL ENGINEERING. Bf

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