Geology
Reprinted from Easy lesson department of the Colliery engineer
Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.
Mine Superintendents, Mining Engineers,
Mine Foremen,
Mine Owners,
It is necessary that you be informed in the progress in the sci ences related to mining, and in the improvements in mining ma chinery and mining methods. To do this you must read the Trans actions of all the Mining and Scientific Societies of the United States and Europe, to become a member of which will cost over $200 a year and you must expend more time thau you can afford in reading these proceedings.
T
Publishe
MIf
scriptior
author.
By rev perform fill a pla with
E
Library Of Congress,
* iapijripfjt In,..
Shelf .XHL6Q
yi tl k
United States Of America.
ning
r de- ; and
le we , , and ished
Condensed as much as the importance of the subject will permit.
Those who subscribe now, can be supplied with bapk numbers from the beginning of volume VIII, issue of August, 1887.
The price of subscription is $2.00 per year.
Sample Copies Sent Free On Application.
Yours truly,
THE COLLIERY ENGINEER Co.,
Coai. Exchange, Scranton, Pa.
Publishers, Importers, and Dealers in books relating to Coal and Metal Mining, Drafting Instruments and Supplies, and Proprietors of The Correspondence School of Mines, and The Correspondence School of Mechanics.
Send For Catalogue.
Mining Primers.
G E Olog Y.
By
M. C. Ihlseng, C. E., E. M.,
Professor Of
Ph. D.
Engineering, State School Of Mines, Golden, Col.
(Reprinted From Easy Lesson Department Of The Col Liery Engineer.)
Entered according to the Act of Congress, in the gear 1898, kg The Colliery Engineer Co., in the office of Librarian of Congress at Washington.
U
Table Of Contents.
Chapter I. — Coal and its Formation
Question. Page.
1. The Composition and appearance of the dif ferent varieties of coal . 1
8. How coal was formed . 11
11. Coal pipes or sigillaria . 12
14. Explanation of fossils . 13
17. Fossils of the Carboniferous period . 15
18. The history of the earth's formation . 15
Chapter II. — Stratified Rocks — Theik Formation and Changes.
Question. Page.
20. How strata were formed . 19
29. The thickness of the stratified rock . 20
32. Formation of the Rocky Mountains . 22
35. Explanation of "folds" or "rolls" . 22
38. Faults . 24
40. Rock faults . 24
*47. Cleat . . 26
Chapter III. — The Amount of Coal is the United States — The Formation of Iron Ore Beds.
Question. " Page
56. How long before the coal will be exhausted . 29
62. The thickness of coal seams in different districts 30 64. The time required to form coal seams . 31
66. What ore is . 31
67. What mineral is . 31
70. The different ores of iron . 32
72. How iron ore beds were formed . 32
81. The proportion of iron in different ores . 33
82. The principal iron producing districts of the
United States . 34
89. The formation of petroleum . 35
Chapter IV. — Natural Gas and Petroleum.
Question. Page.
92. The formation of Natural Gas . 36
94. The territory and formations in which Nat ural Gas is found . 36
100. Spouting wells and dry wells . 37
102. How gas and oil are accumulated underground 38
103. Where to bore for oil or gas . 39
107. The production of petroleum in the United
States and Russia . 40
109. The relation between the origin of coal and oil 41
110. The composition of Natural Gas . 41
Chapter V. — The Distillation of Petroleum — The Comparative Value of Natural Gas, Petroleum, and Coal as Fuels.
Question. Pae,
112. The Uses of Petroleum . 4
113. The Distillation of Petroleum . 43
115. The Amount of Different Substances Obtained
from Pennsylvania Petroleum . 44
119. The Amount of Heat Produced from Fuels . 45
124. Comparison of Values of Petroleum and Coal
as Fuels . 46
127. Comparative Value of Natural Gas and Petro
leum as Fuels . 47
128. Asphalt . 47
Chapter VI. — Plutonic and Volcanic Rocks.
Question. Page.
131. Where Minerals Occur . . 49
133. Massive Rocks . 49
135. Where Plutonic Rocks Occur . 49
136. The Composition of Granites . 50
137. Where Volcanic Rocks Occur . 50
138. The Composition of Porphyries . 50
140. The Primary Rocks of the Earth . 52
144. The Theory of the Formation of Granites . 55
' Chapter VII. — The Occurrence of Ores — How De-
Posited.
Question. Page.
145. Definition of Veins and Beds . 58
147. How Ores were Deposited . 58
149. Where Metalliferous Veins are Found . 60
Chapter VIII — The Formations or Veins and Values of Different Ores.
Question. Page.
157. The Appearance of Veins and Ore Beds . 64
159. Forms and Combinations in which* Gold,
Silver, and other Metals are Found . 65
160. The Values of Different Ores.. . 68
161. The Effect of Different Impurities on the
Values of Ores . 70
162. Changes in the Mineral Character of a Vein
at Different Depths . 71
163. The Formation of Ore- Belts . 71
165. Method of Tracing Intersecting Veins . 73
Chapter I.
1. What is coal ?
Any mineral substance containing sufficient carbon to supply its own fuel and be capable of burning. The line between the various fuels is not easily drawn. There are all grades of coal with vegetable matter at one end of the series and graphite at the other, includ ing peat, lignite, soft bituminous hard coal, and graphite.
2. What is the difference between these varieties ?
If you read the lectures on chemistry you will
notice that every piece of organic matter, leaf, wood, flesh, etc., has carbon, hydrogen, and oxygen in it in different proportions. According as these elements differ in quantity, so they produce wood, grass, or flesh. For example, wood is made of minute particles of carbon, of hydrogen, and oxygen. The same is true of the coals, of which here is a table to show their composition. For simplicity we put C. for carbon, H. for hydrogen, and 0. for oxygen.
Mining Pkimek8.
H.
O.
Vegetable matter has about .
49
06
45
Peat has about .
56
06
37
Lignite has about .
70
06
24
Block coal has about .
75
05
15
Soft coal has about .
88
06
06
Hard coal has about .
95
Graphite has about .
oo
The progressive order of the series is still more notice able when ne reduces the cases to percentages in com bination with 100 parts of Carbon, though the table does show that the Carbon increases in amount.
H.
Vegetable matter .
91*1
Wood .
Teat .
10*8
Lignite .
steam coal .
Anthracite . . .
Grajhite .
3. Why are they so different?
Because these coals were made at different times.
4. How do you know that?
Because they never occur near each other and they look so very much unlike one another.
5. Please explain what you mean ?
Graphite is a pure carbon just like the diamond, and has a fine grain, is smooth and shiny, like steel. It leaves no ash after burning.
Geology.
Anthracite is a hard stone coal, with a very little ash, and burns without smoke.
The bituminous coal is soft, blazes up with a flame, swells, and finally bakes into a spongy mass called coke. There are many varieties called cannel, coking, cherry, splint, or block.
Lignite is a poorer quality of coal that leaves behind a great deal of ash, and is brown in color showing often the fibres of wood in it.
Peat is a matted mass of rotting vegetation.
6. Where are these varieties found ?
Graphite is not very common, and occurs in thin seams.
Anthracite is found in Pennsylvania and Colorado, where the rocks have been disturbed, or broken up.
Bituminous coals are found all over the world, as a wise provision of nature for the comforts of man.
Lignite, or brown coal, is mined in the Western States.
7. Is there any theory to account for them?
Yes, it is one which the geologists have formed from their observations and knowledge of the behavior of the forces of nature.
8. What is it?
Have you ever noticed the marshes and bogs, how they are the rotting masses of vegetable and organic matter ? If they are not disturbed fora number of years the marsh becomes deep and large. In the swamps of Louisiana. Arkansas, an l Mississippi are very deep bogs, in which also grow large trees, close together. When these die, fall, and rot, a thick bottom of carbonaceous matter is deposited. When the water is absorbed, or if the bog becomes dry, a peat is formed, which can be cut and burned. Throughout Ireland, and in many countries are thick, rich bogs of the peat, some quite compact and dry. In any swamp we can find a depth of this black, half decayed wood. Then the land sinks, or the sea rises, and covers the peat with sand and mud,
Mining Primers.
just as we have seen off the shores of Guernsey and off Devonshire. The peat becomes buried, pressed to gether by the materials above it, and in time it assumes the shape like lignite, light, and having one-tenth of its weight in water. A further change, as time wears on, produces the forms of bituminous coal. With greater time, pressure and heat anthacite is formed. If it is still longer heated graphite or plumbago is formed.
9. How long has this change been going on ?
Geologists cannot tell but it must have taken ages.
The amount of coal that supplies U. S. inhabitants alone, is 150,000,000 tons every year, and men tell us that there is sufficient under ground to keep up the supply for an indefinite peroid. The time required to make all this coal out of wood is very great. (See Q. 59).
10. What evidences have you of this theory?
First, the microscope shows coal is full of leaves, fibres, and bark of trees. Then near Richmond wre see a bituminous bed of coal that has been changed in places to anthracite where a thin sheet of lava has touched it. And we can make coal by put ting saw-dust under heat and great pressure.
11. Have those "coal pipes" that occur in the roof any con nection with coal formation ?
Those are called " sigillaria." They are tree trunks that were standing when the mud formed around them. You will notice them in the roof as saucer shaped. As they are the base of trees near the roots and taper thinner upward they are liable to drop down, so always stand from under and prop them at once. In looking for coal (prospecting that is
Fig. 1.
Geology.
called) the finding of sigillaria is a sign of being above the coal. On the preceding page is a picture of them, Fig. 1. The scars are where leaves once grew.
12. There must have been immense forests to furnish so much timber and vegetation ?
There were. If you have seen the large and dense swamps of the Southern States that hid so many negroes during the Kebellion ; or the illustrations of Brazilian and African woods you will readily see that the illustration, Fig. 2, (on next page) is simple in comparison. It shows what the geologists believe to have been the forests of the coal period.
13. Now there are three things troubling me. First, how does this theory come to have been formed ? Second, what do you mean by coal period ? Third, I do not understand what you say about the mud form ing around the " pipes ? "
That is a long story, but I will answer your second first. Have you noticed that coal contains different kinds of leaves, roots, etc.? Well they indicate to us that these plants existed at the time that the trees were growing. We call that the coal period.
14. How was the theory formed ?
It was developed from observation of what is now going on. A leaf falls into the stream and becomes im bedded in its mud. A twig falls on the ground and is covered by sand. An animal dies on the plains, its bones are bleached. A rain washes them into a creek, and they are covered with sand. If in time these are buried under the soil, they give form to the sand that packs around them and a " fossil " is produced. That explains the coal pipes that had been growing in a marsh and stood many hundreds of years after the marsh had been covered by a stream that had deposited mud around the tree. We know that old forest trees live perhaps a thousand years.
Mining Primers.
Geology.
15. animals live daring that time?
Yes ; there were beetles, spiders, and other insects. There were some air-breathing, back boned animals, like our water dogs. There were no birds, no serpents, no fruits, no flowers. Fishes were plenty.
Id. Are there any fishes in the coal ?
Occasionally they are found to give life to the dead wate, but they are generally found in the slates and (lays above and below the coal.
17. Is that the reason that certain rocks are called carboniferous, or of coal period ?
We always know how and where to look for coal. The finding of fossils is our guide. For example if I find in a certain rock, remains of the five-fingered leaves, like that shown in Fig. 3, I know I am too high to look for coal and must go down. And if a rock is found with the lower forms of life, like those of Fig. 4, I am too low down in the rocks. Carbon iferous rocks will have shells like those shown in Fig. 5.
18. What do you mean by say ing " too low down ? "
The question involves the whole history of the earth's forma- Fig. 3.
tion. All the rocks are in layers
which occur in the same order wherever vou go. Some layers may be missing or very thin, and in other places they will be thick. The order is, however, the same. Granite is always at the bottom and is called the base ment of the earth. Then come a variety of sandstones, slates, clays, and limestones, of different colors and natures.
Some of the bottom layers of these have fossils like those in Fig. 4, and are called Silurian. Above them
Mining Primers.
Fig. 4.
Geology.
will come layers having fishes, called Devonian ; corals were also numerous. On top of these, never below them, came again series of slates, limestone, etc., (car boniferous) that are full of plants, fossils, or shells like
Fig. 5.
Fig. 5. Above them came layers and layers of these same rocks carrying corals in sixes , not in fours as were
Mining Primers.
those of the Devonian , and equally -split- tailed fishes, and above all reptiles like those in Fig. 3£.
These layers included the Jurassic , Triassic, and Cre taceous periods. During the last-named there also exist ed great forests to produce the coals of the Western States.
After the Cretaceous we had birds appearing in the Tertiary rocks, and finally mammals.
So you see there is perfectly uni form order which can always be identified by the kind of fossils the rocks contain. The more nearly the animal or plant resem bles those of our . ay the higher up the rock is.
19. Are these rocks always of same thickness?
No, for they were made under different conditions of the earth and may be one foot thick in Pennsylvania and 50 feet thick in Germany. The car boniferous is very rare in Colorado. Again the rocks were formed like the peat as mud deposits of a creek, or lake, or ocean, so they will be thin near the banks and thick in the deep water.
Fig. 6.
Chapter Ii.
20. What are strata ?
That is a term used in speaking of several layera. One is called a stratum. Two or more are strata.
21. Is that where "stratified rocks" comes from? As the rocks like limestone and slate are flat layers
we call them stratified.
22. Is granite stratified.
No, it is a massive rock.
23. Then it was not produced by seas or creeks ?
No, granite is the foundation rock of the earth and when as the Bible says, this earth assumed form, it be gan to be worn away by frost and water. The coarse heavy material was washed to the bottom of the hill and there it was left while the sand and mud were car ried further on. Soon the current became too slow and the sand accumulated while the lime grains were
carried along with the clay mud. Afterwards the lime settled out and the mud formed a bottom way out in deep water. If the operation continued long we had
Mining Primers.
sandstone, limestone, and clay. Then if there was a drought, or the sea dried up, all the plants and animals went with the soil and they were buried.
Then a flood and a new sea formed later and began the same process of eating away the granite to form, perhaps, the Devonian, and so on. It is the same as is going on to-day. (See question 8, Surface Appliances.)
24. What are the slates made of?
They are the same as clay but they have been hardened more than the clays.
25. Then, the coal must have been formed in v£ry quiet water, a pool or ocean?
Yes, how did you come to see that?
26. Because usually our coal seams have clay or s'ate roof and floor. Then in years to come will we be fossils for future geologists ?
Yes, drowned sailors lying in their wet graves are being slowly buried with whales and corals in the eversettling sediment. The whole history of the earth has been one ceaseless action of rain and sea that carries everything to the ocean, the bottom of which is and has been a cemetery in which lie the dead from the three kingdoms of nature — the earth, air, and water.
27. How long has this been going on?
We can not tell, certainly a long time.
28. Is the whole crust of the earth stratified above the granite?
Yes, and all are called sometimes sedimentary rock as well as stratified. The first name refers to the mode of formation, the second to the manner of its occurrence.
29. How thick is the stratified series?
The crust of the earth is 50 miles thick and the strat ified rock constitutes from a mile to ten miles of it.
30 Has any one ever seen the bottom granite?
Oh yes. Sometimes the stratified rocks on the granite are not deep nd a bore hole has been drilled down into it Sometimes very deep holes, nearly a mile, have
QV f°vr vv
v V
✓ V'
V
V,
C 1/
,0.-*4
Mining Primers.
failed to reach even the carboniferous.. In other places there are no stratified rocks to hide the granite.
31. Why is that ?
Such places may have been the original hills of the earth against which all the seas have beaten. In Canada and the Adirondack Mountains are remains of these primitive hills.
32. May they not have been thrown up through all these strata?
Not there; but the Rocky Mountain range was formed in that way.
33. Did the mountains break right through all the strata ?
Yes, for all along them North and South you will see the rocks standing up on end like in Figure 8. At places the wall stands 300 feet high. It is this which makes the Garden of the Gods so famous There, the rocks stand hundreds of feet high in walls and towers.
34. Is the Silurian next to the granite ?
No, not here. Elsewhere it is next. The carbonif erous was broken off below, but was not pushed up to the surface. In this figure you will see that the granite has shoved up through the strata and broken them off. The further away you go from the mountains, as away out to the right of the figure, the rocks are less disturbed and you will notice that they become flat. So they extend under the plains, under Missouri and Ohio for nearly 2,000 miles to the Alleghany Mountains where they again stand up. Some of the Anthracite coal seams are steep instead of flat. The coal marked to the right is cretaceous. We know, too, that the Rocky Moun tains were tipped up because on the other side the rocks are broken off dipping towards the West. And also a few patches were carried up on the tops. Fig. 10.
35. I should think the strata would be broken up by this uplifting. Are they ?
Yes they are. You must remember that the quiet
Geology.
depositing of mud as I explained was going on whiie the earth was cooling. As it cooled, the strata shrunk and in doing so became squeezed. The layers were bent and distorted just like a number of sheets of paper would behave under a side pressure that squeezed them.
36. What are these called ?
They are called " folds " or " rolls." You must have
B
Fig. 9.
noticed them in the mine. Fig. 9 is from an actual case. Fig 10 is also another case from on top of the Rocky Mountains a mile above sea level. The dotted lines show where it is believed the strata united A B and C are valleys and creeks. At Tamaqua, Penn., the Mammoth coal bed, as it is called, is bent like the letter U coming out on Sharp Mountain at one end and Locust Mountain at the other.
Fig. 10.
37. With these bends and rolls I should think the strata might be broken ?
Mining Trimers.
They often are broken fine or else they crack just as is shown in Fig. 11.
Ftg. 11.
38. What are the cracks called?
" Faults " is the proper name for these breaks but miners call them " thrusts," or " throws."
39. Why are they so called?
Geologists call them faults. They are breaks in the strata, across them. For example, if the rocks in Fig . 9 were to break, the fault would be along A B. But it seems that besides cracking, the strata fell and are mis placed as in Fig. 11, where A and B are coal seams. The right hand side slipped on the fault line. As these faults generally cause a settling of one side or the other, the miners have called them " throws " as if one side was thrown up or thrown down.
40. What do the miners mean by " rock faults " or slate faults ? "
These are not, truly, faults but they are names which the miner uses for portions of the coal beds which are thinner and have slate or sandstone where some of the coal ought to be, as S in Fig. 12. They call them " horses " in ore mining.
Geology.
41. Faults, then, are places where the rocks have been broken and afterwards displaced? Is there ever any thing in those cracks?
Oh, yes. In regions where volcanoes exist and where earthquakes are common, the faults are often filled with
Roof
Fig. 12.
lava from the volcanoes or with .silver and lead ores. In the coal regions, however, they rarely have anything but dirt and fine rock.
42. Are faults common?
I know of only three in the Pennsylvania Bitumin ous region. There are several in tlie Anthracite districts. They are quite numerous in the Western States but not common in Virginia, Illinois, or Missouri.
Fig. 13.
43. How far do the rocks slip ?
They may be as much as 20,000 ft. The average may
Mining Primers.
be said to be 20 feet. But in Utah there is a throw of 10,000 feet. And in Pennsylvania and Virginia the sinking is over 30,000 feet.
44. Are they ever near together ?
Look at Fig. 13 which is a good example from England.
45. How do you know but they may be separate beds which never were connected ?
Do not you recall what I s-aid about fossils ?
Well, each different rock will have some distinct variety of shell fish or leaf by which we can recognize it. When the rocks are similar they have the same kinds of fossils.
46. Then by the fossils you know where to look for the rest of the coal seam ?
Yes, if I am mining one of those coal seams and strike a fault, I go over to the other side, examine the rock and then by its fossils I can tell whether the thrust has been up, or down. And I go accordingly. Don't you see how important fossils are ?
47. Have these faults anything to do with the cleat of coal ?
Not at all. By the name of " cleat " we mean the joints in the coal All rocks have joints and split along them giving smooth surfaces. Slate cleaves into thin slabs, and building stones have also that tendency. But besides breaking into slabs, many stones break cross wise into blocks more or less like a cube. The joints along which the stones naturally break are called cleav age joints or "cleats." These joints are natural to every material. Even volcanic rocks, as we shall soon see, have cleavage planes.
48. Are the cleats the same distance apart in all coals ?
No. The soft coals have the cleats nearer together
than the hard coals. But for a particular coal they are the same distance apart. Sometimes they are in such directions as to give a cubical shape to the coal. At other times, the cleats are at an angle.
Geology.
49. What is the cause of cleats?
It is the natural condition of the coal just as the " mundic," " iron," or "pyrites" in the coal always occur in the form of cubes.
50. Are cleats of any help to the miner?
Yes, indeed. The coal breaks off easily at these joints and so the hewer will cut under as far as a cleat and then let the coal fall. To make this possible, it often happens that direction of the cleat fixes the direction of the working faces. So the rooms are turned off fromthe gangways as that their faces shall be with cleat. Mines working by the "pillar and stall " method can take advantage of the cleat in this way. Those work ing Longwall can not always. In Anthracite, the cleat is not an important enough matter to determine the direction of the working faces. The coal seams are generally too steep there.
51. How does the coal look on the cleat?
Smooth and shiny.
52. Can you explain the methods of mining as you mentioned them ?
I leave that to another time.
53. Is the coal often crushed badly by these folds, bends, and faults ?
Oh yes. In the hollows of the sharp bends there is a great deal of finely broken coal. The quality of the coal is very much injured and the loss by waste is often very high from this cause.
54. May it be that the " dirt faults " and " rock faults " are caused by grinding of the strata on each other ?
Yes, the name of dirt fault is often applied to places where the coal has been badly broken up. Sometimes, though, the term like that of rock fault or slate fault is used to express the idea that the coal has thinned out and is replaced by dirt, rock, or slate.
55. What are " partings " ?
They are seams of clay or slate found in the coal beds
Mining Primers.
that divide the coal into several layers. Rarely is a coal bed without them. They occupy on an average one-seventh of the entire thickness of the bed. These partings are mud deposits that show the bottoms of the ancient marshes had been raised or that the currents flowing through them had changed in direction or speed.
Chapter Iii.
56. What is the amount of coal yet remaining inKthe U. S.?
That is hard to say. But the Census Bureau esti mates 250,000 square miles of coal beds of all varieties and thicknesses. Assuming 5 feet as the average thick ness of the coal, and an average of only 1000 tons of coal that can be recovered from every acre of coal bed of one foot thickness, we have :
250,000 X 640 X 5 X 1000 800,000,000,000 tons as the total amount of coal.
57. How long will that last ?
Last year there were sold and used 128,000,000 long tons. At that rate there is supply for 6250 years. But population is increasing, and the demand increases like wise. From the past experience, it has been found that the consumption doubles every 16 years. On this basis, in 190 years all the coal will have been burned up unless other sources of power and of heat are mean while discovered or more economy shown in the burn ing of fuel.
58. Am I to understand that all coals are made of the same vegetable decay ?
We believe so, that club mosses, ferns, and trees like our ground pine furnished the most of the mineral coal of the Carboniferous age.
59. How about the can n el coal ?
That is a compact smooth breaking coal which will light with a match just as a candle would. It is formed of the finer grained marsh weeds.
Mixing Primers.
60. I can not understand how so much coal could he formed from one marsh. For the peat and wood must have lost much of its oxygen and of its weight in being compressed to coal ?
Yes, so it has ; wood actually loses three- fifths of its weight in being altered to Bituminous coal, and threefourths of it is lost in being changed to Anthracite. Besides this, the decayed matter is compressed and loses in bulk. So that, altogether, it took about 5 feet of veg etable marsh to make one foot of Bituminous coal and 8 feet to produce one foot of Anthracite.
61. How thick is the coal?
Coal occurs in marshes very thin at the edges and thick in the middle. In some places a single bed is as thick as 40 feet (one in Colorado is 90 feet thick) but a pure seam is seldom over eight feet. Anything over that is a compound seam, in which the streaks are sep arated by thin partings.
62. How many coal seams are there in a district?
In Pottsville, Pennsylvania, there are 113 feet of coal seams; and in the U. S. the largest number of seams, one above the other is 42. In Wales there are 100, of which 70 are worked. In Nova Scotia there are 81 workable seams at various depths from the surface.
63. Did you say that these different seams were caused by the ocean overflowing the land several times ?
Yes. The forests and swamps were covered by sedi ments and became hidden from view. The marshes sank during the disturbances that followed. Then the ocean flowed over it and brought more mud. The peat bog compressed and coal began to form there under the clays. After a rest, during which more mud and sand was deposited, more disturbances occurred. Some ground went up, some fell. Forests began to grow and more ferns flourished to form marshes.- After these had decayed, another sinking is supposed to have taken place, and another mass of peat was buried to after-
Geology
wards form coal. This must have been repeated as many times as there are seams of coal. Sometimes salt water covered the marsh, sometimes it was fresh water.
64. How long did all this take ?
I have seen estimates making it' over a million years.
65. How is that measured ?
An ordinary forest will make about 2000 pounds of organic matter per acre each year. This is 200,000 pounds in a century. One hundred tons compressed to be as heavy as coal will make 2420 cubic feet. If these are spread over an acre of 43560 square feet sur face, they will form a layer only two thirds of an inch thick. But in the formation of coal four-fifths of the material escapes as gas, oil, or water, and only one-fifth remains in it, therefore it must take 500 years, instead of 100, to make a layer of coal two-thirds of an inch thick. For a coal seam of the standard size, four feet, it must therefore have required 72 times 500 years to make it, or 36,000 years. But some coal regions have over 100 feet of coal. To form the coal alone would --therefore require aboutfKX), 000 years. Think of it ! And we are using it up so very fast that we have perhaps only enough for the sixth generation beyond our own.
66 What is meant by an ore?
An ore is an accumulation of mineral in such quan tity and of such a quality as to pay for mining.
67. Wb at is a mineral? .
A mineral is the compound of a metal in chemical union with a non-metallic substance, as sulphur, car bonic acid (the choke-damp of min.es), etc.
68. Will vou give some samples ?
Iron and sulphur make a mineral called pyrites; lead and sulphur give a mineral known as galena ; iron yith oxygen makes a very common iron riiineral, and silver with arsenic and sulphur is often seen. And When a big bed of any of these minerals is found it. is mined for the ore of iron, of lead, or of silver,
Mining Primers.
69. Is pyrites a common ore of iron ?
No. Pyrites is the commonest occurrence of iron in the earth, but it is mined not for iron manufacture but for the sulphur in it. Hence it is not an iron ore. It does not pay to roast off the sulphur and make iron of if when there is so much of a better mineral to be had.
70. What is the ore of iron ?
The several ores are all varieties of the compound of iron with oxygen. They are called hematite, limonite, or magnetite.
71. Where are they found?
In the sedimentary rocks between the strata, like coal ; and often very thick.
72. How were these beds formed, like coal ?
Not exactly like coal but yet very similar, in that water and vegetable and organic matter have had a great deal to do with the deposit.
73. What is the process?
We judge only by what is going on now. Taste the waters of a bog as they ooze from the soil. The taste is inky. The water is colorless. A chemist would tell you that there is iron in it. Where did it come from ? I will tell you. Where are the iron bogs seen ? Any where and everywhere. Do you remember my saying that pyrites was a very common mineral? It is every where, — in coal, in clay, in sandstone and in nearly all the rocks. Water is a great and powerful solvent. It can leach out of any rock some of the matter it con tains. Well, it will dissolve, or wash away pyrites which naturally accumulate in the marshes.
74. But we do not find pyrites there ?
No you do not for the moment, wet pyrites comes out into the air it rusts (that is, it takes oxygen from the air) and you will notice a scum floating on top of the water. That is iron rust. By and by the rust sinks to the bottom and as more of it is washed in here, a layer of iron mineral is formed.
Geology.
75. Why, it is just like coal formation!
Yes, this bog iron ore forms in pools like coal but there is a difference. It seems that organic matter is important in this work. Decaying plants and animals seem to hasten the process which othtrwize would be slow.
76. Are all the varieties of iron formed in the same way ?
Practically the same. The varieties differ in the amount of oxygen contained with the iron. This dif ference causes some iron ores to be reddish, like ochre, and others metallic.
77. Are iron springs the same thing you have been describing ?
Yes, they are. You will see them near the place where coal -beds come up to daylight. Indeed one way to some coal blossom is to be on the lookout for these iron springs or iron bogs.
78. You told us of the effects of heat on coal, does it ever change the iron ores ?
Wherever a bed of iron ore has been heated by hav ing lava near it or where it has been squeezed " badly in the disturbances of the rocks, the soft limonite iron ore wras changed into the hard shiny "magnetite" or " hematite."
79. In what geological formations does iron ore occur ?
Most of the English iron ore comes from the coal
measures. Alabama iron ore is also from near the coal seams. The Silurian contains much of the iron ore.
80. Does an iron bed have fossils in it as in a coal seam ?
Yes. but the fossils are always of fresh water plants and shells.
81 How much iron is there in the ores ?
Magnetite is nearly three-fourths pure iron ; hema tite or specular ore has nearly as much ; bog ore has a little over one-half iron.
Mining Primers.
82. Where are these ores mined ?
In almost every state of the Union. Some ores are purer than others, but the Lake Superior region, Corn wall of Pennsylvania, and Virginia, are turning out large amounts of iron ore. Michigan stands first in mining nearly 6,000,000 long tons of an average value of $2.70 per ton. Alabama and Pennsjd vania come next with 1,500,000 each.
83. Do all kinds of iron ore produce the same kind of iron ?
No. The red hematite is the most desirable iron ore.
84. How much iron ore have we in the United States ?
We produced 14,518,500 long tons last year. The consumption is 15,733,465 (according to the census). Each long ton of ore is equal to about 1,200 pounds of pig iron.
85. Have any figures been given as to how long the iron ore supply will last ?
It is predicted that we have only sufficient iron ore, now discovered, to furnish the United States for 110 years, assuming that the consumption doubles every 13 years, which it would do if it continued at the same rate as during the last 10 years.
86. How thick are the iron ore beds ?
Like coal, they may be found up to 50 fc et thick, though the purest seams are only about 4 feet. Like coal, also, the seam is underlaid by clay.
87. From what you say of iron and coal, the plants and animals must play a very important part in Nature ?
They do, and though we are exhausting the coal beds and iron mines, they return to the earth again. When we burn up coal, it goes up into a gas, that i? called car bonic acid gas, what miners call choke-damp. That gas feeds the plants now living and they take the carbon out of the gas, put it into the grass or wood which soon decays and goes through the same process. ' So it is
Geology.
with iron, when it rusts it falls into the soil and is washed back into some pool and we have iron ore again.
88. Does anything else depend upon the plants ?
Y es, natural gas and petroleum. They are the pro ducts of decay of wood and vegetation. Some claim that petroleum, or mineral oil, was made by the decay of organic matter, perhaps of animals.
89. Why is that so thought ?
Because bis caves have been found containing bitu men, the solid remnant of petroleum and with fossils. In one place there has even been a cave solidly full of fishes that have been changed into oily tar. At least the geologists are all agreed that petroleum was made from organic matter that lived in salt water.
90. What is the objection to the belief that the oil came from trees and plants?
Because petroleum rarely occurs in strata that have been heated.
Chapter Iv.
91. What is natural gas ?
It is a gas accumulated in the subterranean cham bers. It was discovered while drilling for oil wells. All oil wells may yield gas, but gas wells do not give petroleum.
92. How was it produced ?
Do you remember Q. 8 in which it was shown that the movements of the rocks in the earth heated and changed the character of the coals from peat or lignite to Bituminous and from the soft coals to the hard coals ? In this process, the most of the carbon remained in the coal as the table in Q. 2 showed, while the oxygen and some hydrogen forming water was carried off while the remainder of the hydrogen and some of the carbon, combined as a gas or in different gases escaped into the strata where it was collected in the pores or in cavities.
93. Is the natural gas, then, a remnant of the coal changes ?
Yes, it is, and is found in the vicinity of the coal re gions. A few geologists believe that fishes furnished the oil.
94. Does the gas cover a large territory ?
It is found in a greater area than that of oil. And by the finding of new wells the district is extending. There are 500 gas- wells in the oil country and its vicin ity and these produce 100,000,000 cubic feet per day.
95. At what depth is gas found ?
Geology.
The depth is 2200 feet or so, though of course it varies.
96. Is there any connection between gas and oil?
Yes, the late Mr. C. Asburner who was the authority,
says they are the same in a geological sense.
97. Where does the gas occur, geologically speaking ?
It is found in the flat or nearly flat beds of three differ ent sets of strata. The most productive wells are in the
Devonian sands. (See Question 18.) It is found in the lower Silurian lime stones. It is in the Bradford and Shef field sandsand 1,500 feet below the Pitts burgh coal. In no case, however, does it occur where the rocks are broken up badly or where the strata are not porous. We find oil and gas in the Cretaceous in Colorado.
98. Why is the oil in a given stratum ?
Because the rock B is porous and has a floor A of clay, if now the rocks above are so badly cracked as the oil to flow in from above, the oil will accumulate in just the same way as the artesian well waters do, Fig. 14. When a hole is drilled to the porous stratum, the oil, gas, or artesian water, according to the region, will flow out.
99. Does the natural gas occur in the same way ?
The stratum is there overlaid by a loof or cover of
impervious material like clay, and the rocks below are broken or porous enough to let the gas rise as high as it can.
100. What is the difference between a spouting well and a dry well ?
Mining Pr1Mkr8.
When boring for any of the three substances one may finally drill down into a stratum that contains them. If they are under pressure they may spout up to the surface, otherwise not. For example, the well W, Fig. 14, is drawing water from the stratum B ; if the accumulation is deep and extends up above the level of W. as at C, for instance, then the well will spout. But if the surface is more like that at D and W is higher, the water will only rise to some point like F. Now the first example is one of a spouting well, the second, of one that is a pumping well, it requires power to raise the water. A dry well would be one that either did not reach B or else went through A and let the water out.
101. Is that the same with petroleum and gas ?
Somewhat, though it is not like water in that there is
no perennial supply. The rain is continually feeding the stratum B with water, but there is nothing to keep up the supply of oil or gas. The accumulations of ages may be exhausted in a few months. The spouting oil wells are the lucky strikes into the reservoirs of nature that have been long collecting.
102. How is it accumulated underground ?
In Figs. 15 and 16 you will see what I want now to
explain. Rocks are quite porous, and some have caves caused by the action of under ground currents of water. Sandstone is very porous, and so is shale, therefore oil and gas can circulate freely in them. Besides this limestone has caves in it something like Fig. 15. Water is a strong solvent as you have already seen in the
Fig. 15.
Geology.
description of iron ore formation. If it flows long, it eats away the cave like at M and as it trickles from the roof of the cave it forms icicles of lime called stalac tites. The Mammoth Cave, of Kentucky, and Ouray Caverns are good examples. Some caverns may not have stalactites. In the rocks are such caverns which somehow accumulated the oil and gas like in Fig. 16. Oil is lighter than water and so will float on top of it. So also gas will gather above the oil as in the figure. Now one man may sink a well at B and get gas only ; another hole drilled at A will get oil and later gas ; the hole sunk in C will strike salt water. As these have accumulated from the de composition of coal or organic matter with great heat, the gas is under heavy pressure, just like steam in a boiler. It forces itself out through B, or else A or C, driving out the other materials first. It may be a long time before the oil is all forced out at A but in time the gas will escape.
This has been the his tory of several neighbors in the oil country.
103. Where should one bore for gas or oil ?
If one can strike the rocks of the oil-bearing series, one should try to reach a spot on the top of the folds of the strata. Experience does not prove this to be always true, but it naturally tends to accumulate in the gently crumpled strata.
104. Why does the explosion of a cartridge at the bottom of a dry hole bring oil or gas ?
In the oil country, you expect to find oil in certain
Ttt
Ttt
rr-T
rii
Tt
Tt
rn
1 1 , 1 ,
L, 1 )
1 j 1.1
Tt
1=3
J-Uu
Ttt
Tri
"TSv-G
w
J"fegA LT W A T 1 t R -tS - T- — 1 ! — — I—
l -J 1 - . 1
Fig. 16
Mining Primers.
rocks. If, however, you fail to get a pumping or a spouting well you simply have not bored into one of the caves or reservoir.'. But you may be near one. So by putting 50 or 100 pounds of nitro glycerine in the bottom of a hole and dropping a drill rod on it you may, possibly, break into a neighboring reservoir and so get oil, but it is not certain. This method is never advisable in shelly ground unless the hole is lined with tubing, for the blast will cause a caving that will be forever troublesome and has often resulted in the abandonment of the hole.
105. Are there any surface indications ?
Yes, what is called oil show is one. On the surface of pools or springs a scum floats and gives good sign ; while again there are what may be called burning springs — rising gases which may be set fire to.
106. Where does the petroleum come from?
Russia and America are the chief oil-producing countries of the world. But other countries have large supplies. Geologically speaking it occurs with natural gas.
107 How much oil is produced in America?
Last year it was 1,160,000,000 gallons. And since 1870 it has been steadily growing from 1000 wells giving 201,471,000 gallons until there has now been produced altogether 18,400,000,000 gallons. Russia, during 1886 alone turned out 260,000,000 gallons ; Scotland has slates that are mined and hoisted to the surface where the oil is sweated out of them. The Kimmeridge clay of Eng land, is able to furnish a one-half barrel of oil from every cubic yard.
108/ Is the supply without limit?
Geologists estimate an area of over 200,000 square miles as having more or less oil. The amount can not be estimated but is still very large, and the number of spouting wells, while uncertain, has not been decreas ing. The Census reports show that the United States
Geology.
produced $223,066,388 worth of petroleum during the past ten years and $76,563,674 worth of natural gas. Some of this came from Colorado and California but far the largest amount is produced in States bordering on the Ohio River. The natural gas supply will be much more quickly exhausted than the oil and that of Ohio and Indiana will not last as long as the Pennsylvania gas fields. The average pressure of the gas in the wells owned by the City of Toledo, Ohio, is now only about 115 pounds to the square inch. In 1889, it was 250 pounds, and in 1890 it fell to 175 pounds. Many of the gas wells originally had a pressure of 400 pounds.
109. Why is the origin of oil associated with coal?
Do you remember how in Q. 8 we showed the coal to be a marsh product? You are aware of the miasma and gas that comes from a marsh — we call it marsh gas. Now, coal, when burned in the stove, or a coke oven or in a gas works, or in the analysis gives off some gaseous material, coal gas ; some volatile liquid, as naphtha ; some liquid as coal oil ; some tarand a little pit h. We find in nature a similar series — gas called natural gas, or fire-damp if it occurs in a mine; that which comes out at springs or from bore-holes some light oils as rock-naphtha ; liquid petroleum ; tarry substances like bitumen ; and some solid material like asphalt. From these similarities we believe that petro leum had an organic origin.
110 Has natural gas the same composition as marsh gas?
Natural gas is composed of :
Marsh eras . 95 "50$
Hydrogen . 200
Oxygen . 1'50
Carbonic Acid . 100
Marsh gas is a compound of 1 part of carbon with 4 parts of Hydrogen. Fire-damp is nearly pure marsh gas. (See Q. 65, Ventilation.) You see the gases are
Mining Primers.
about the same in composition, but fire-damp stayed in the seams and pores of the coal while natural gas succeeded in escaping. In the Anthracite region the rocks were nearly all broken up, thus giving escape to most of the gas which remained in the Bituminous dis tricts.
111. Is natural gas as dangerous as fire-damp ?
Exactly as bad. The blowers, as you call them, that let in fire-damp at the faces of the coal is practically natural gas. That is why there is so much complaint about the leaky main pipes that carry natural gas. At the points of leakage the gas works into the ground and affects the air of shallow mines near by.
Chapter V.
112. What is petroleum used for?
In the crude state, it may be used for common lubri cants as for car wheels, etc. But most of it is distilled and from it a large number of substances are made. These substances are chemical mixtures of carbon and hydrogen in different proportions.
113. How is it done?
If you notice what was said in answer to Q. 100 you have an idea of the process. The petroleum is put into a huge boiler and heated very carefully to a tempera ture of, say, 120° F., and kept there. At that point a number of light volatile oils are boiled out. These are the series of naphthas which evaporate readily, are easily ignited and, when mixed with air, form ex plosive compounds. Then at a higher temperature ben zine comes off. After that kerosene, or coal oil, which boils at 340° F., is driven off. By heating still higher, the heavy lubricating oils are obtained. At still greater heat, tarry matters and various coloring compounds are boiled and a refuse remains with more or less offensive odors. Remember, that each different quality of oil is obtained by keeping the petroleum at a fixed tempera ture. This separation is not very perfect. The lightest of the oils are the purest and those which come off later have always an admixture with other oils, for neither can the temperature be maintained perfectly regular, nor can the volatilization be perfectly theoretical. And that is the trouble with our burning oils. If all the naphtha is not carefully driven out before
Mining Primers.
the manufacture of the kerosene begins, the coal oil will have some of these light products mixed with it and when you leave your 5 gallon can of oil near the stove or in a hot place some of this remaining naphtha which should have been driven off in the refinery, es capes and if you light a match near it — pop goes the weasel. That is why kerosene is always labeled for "fire test." If you value your property or life, be sure to buy only high test kerosene. Often these oils are spoken of as having a certain flashing test. By that is meant the degree of Fahrenheit at which the oil will give off dangerous gas. An oil is not safe if it has a flashing test of less than 103° F. The more naphtha an oil has, the lower is its flashing point.
114. How are the other products obtained?
Paraffine is obtained by chilling a certain grade of oil.
Astral oil is only one variety of coal oil having a flash ing point of 125° F. Gasolene is a very, light oil ob tained from a careful heating of the first naphthas that come off. Then all the various bands of oil are similarly produced according to the temperature of boiling.
115. What amounts of the substances are obtained?
A Pennsylvania oil will give :
Gasolene .
Refined naphtha .
Benzine .
Kerosene .
Lubricating oil
Paraffine .
Gas coke and loss
. 15 per cent. .lO1 per cent.
4- per cent. .55- per cent. .17 5 per cent.
2- per cent. .10- per cent.
116. Could these gases and oils also be made directly from coals ?
Yes, to a certain extent. But that wrould require greater care and would cost too much. The gas works treat coal this way and drive out natural gas, produce tar and other substances beside the coke. In the old countries the peat bogs are utilized in this way to make
Geology.
tar, paraffine, solar oil, acetic acid, naphtha, and gas. Vaseline, kerosene, aniline and many other materials are also made from petroleum.
117. What is the price of petroleum ?
That varies with the market. In 1864 when 1000 wells were flowing the price was about $9'84 per barrel of 40 gallons .Now, with 3800 wells gushing oil, it aver ages about 80 cents according to the Census j eports.
118. In what way are gas and oil used for fuel ?
Just as coal is use 1. They have carbon, hydrogen
and oxygen and if these be burned with air, heat is produced.
119. Explain, please?
One pound of carbon, pure anthracite, burned in the air gives out 14,540 units of heat. Whether that carbon is burned slow or fast it will give so much heat and will, under a boiler, evaporate 147 lbs of wrater from the boiling point. Now if wood, or oil, or gas, of peat has one half a pound of carbon in it, then 735 pounds of water will be evaporated by it. Any substance contain ing hydrogen will also be able to evaporate water, and produce heat, because one pound of hydrogen, no mat ter how it is combined, in peat or in gas, will give out, when burned, 61,200 units of heat and evaporate 6T8 pounds of water from 212° Fahrenheit.
120. How about the oxygen in the oil or gas ?
That is not a heat producer by combining with the air.
In fact the carbon and the hydrogen burn only, be cause they rob the oxygen from the air. That is what we do. Our lungs are furnaces. We inhale oxygen and that with the carbon from the body forms carbonic acid just as the stove burning wood or the locomotive burning coal.
121. How would you find the amount of heat in coal then ?
Find how much carbon is in a pound of coal and how much hydrogen also, and multiply these parts by
Mining Primers.
the amount of heat to be obtained from burning one pound.
122. Suppose 100 pounds of petroleum ; now, how would you do it ?
One hundred pounds of petroleum have 86 pounds of carbon, 12 pounds of hydrogen and 2 of oxygen. One pound of carbon gives 14,540 units ; therefore 86 pounds of carbon will give 1,250,440 units of heat. 12 pounds of hydrogen will give 734,400 units of heat. So one hundred pounds of petroleum gives us 1,984,840 units of heat.
123. What is a unit of heat?
The amount of heat necessary to raise one pound of water 1° Fahrenheit.
124. How does petroleum compare with oil and coal ?
One pound of
Petroleum will evaporate . 22 7 pounds of water.
Coke will evaporate . 1B 2 pounds of water.
Anthracite will evaporate . 14*2 pounds of water.
Bituminous will evaporate . 15 5 pounds of water.
Peat dried will evaporate . 10 0 pounds of water
Wood, dry will evaporate . 7 5 pounds of water.
125. Does it make any difference where or how these are burned ?
Theoretically, no matter where or how the wood, peat or coke is burned, the same amount of heat is pro duced. Practically, however, there is a difference. Some burn up fast and some slow ; some give a long flame while others give none at all. These affect the burning qualities under a boiler. So the "calorific value" of a coal depends not only on the heat it is cap able of producing but also the kind of grate it is burned in and whether it gets draught enough.
126. How much heat should one get from a long ton of coal like the soft bituminous coal described in Ques tion 2 ?
That coal contains 88 per cent, of C. ; 6 per cent, of H.,
Geology.
and 6 per cent, of 0. One long ton of coal contains, therefore, 1972 pounds of carbon, 134 pounds of hy drogen and 134 pounds of oxygen. All of the oxygen in the coal exists as water and as it takes one- eighth as much hydrogen as oxygen to form the water, so we must deduct 167 pounds of hydrogen for the water, because one-eighth of 134 pounds is 1675 pounds. The 117 '25 pounds of hydrogen remaining give 7,175,700 units of heat and the 1972 pounds of carbon produce 28,672,880 units. So that one long ton of this coal will boil away more than 36,200 pounds of water from the boiling, point, provided all of the heat goes into the process
127. Then does natural gas serve as a fuel on the same principle?
The quantity of freed hydrogen and carbon, as in the example above, determines the "calorific value" of the gas. A natural gas contains 709 units of heat for every cubic foot. That is when 1000 cubic feet of gas are burned, they give out as much heat as 55'4 pounds of the coal mentioned above. As the gas is free from sulphur it does not give as much trouble in iron smelt ing as would coal. Practically, the Westinghouse Brake Co. evaporated 10 38 pounds of water for one pound of the coal and the same amount with 178 cubic feet of the gas. Whence it follows that 1000 feet of the gas is equal to 81*8 pounds of the coal. So that gas burns to better advantage than the coal. It takes, in other words, 81'8 pounds of coal to do what 55*4 pounds should do compared with gas.
128. What is asphalt ?
Asphalt is a solid bituminous substance that is the residue of nature's distillation of coal by volcanic heat, or by subterranean heat due to pressure and contrac tion of the earth's crust. It is of variable composition because it is not a simple substance any more than is coal. It is a mixture of several hydro carbons.
Mining Primers.
129. What is it used for?
The most extensive use is for sidewalks and pave ments, and it is an excellent soft water tight flooring for cellars.
130. Where is it found ?
It occurs widely diffused throughout the world, more especially in the tropical regions. In the Isle of Trinidad is a remarkable lake of it, 66 acres in area and of unknown depth. This lake is semi-fluid, and in places, quite liquid. At the edges exposure makes it hard. Varieties of asphalt are found in other places as a bed between two strata. Then there are a number of harder varieties called ozocerite, bitumen, etc., which occur to a greater or less extent as a vein or a bed. Similarly, naphtha is found in some localities flowing out of the earth as a olear, colorless liquid. Finally, the asphalt deposits which assume the greatest indus trial importance are those in which a limestone is im pregnated with asphalt. These bituminous stones carry from 8 to 20 per cent, and may be at once crushed and prepared for the purpose of road pavements, etc. The U. S. have produced, during 10 years, 127,500 short tons of asphalt and 47 short tons of purified ozocerite.
Chapter Vi.
131. Where do the minerals of zinc, lead, silver, and gold occur?
The total zinc product of the world is obtained from the flat beds and deposits intercalated with the sedi mentary strata. A large proportion of the lead is also mined out of the stratified rocks, while many of the ores of the precious metals occur in the same way.
132. Do they only occur in the stratified rocks ?
They are often found in the metamorphic regions
and in the massive rocks.
133. What are the massive rocks ?
They are a class of rocks which have no tendency to break into plates or slabs, as would limestone or slate but are usually coarse grained crystalline and quite, solid.
134. What are they called ?
There are two varieties; called plutonic and volcan ic. The first term embraces the granite, syenite and gneiss made up wholly of a mass of crystals of dif ferent substances. The second includes fine grained, partially crystallized, and somewhat glassy rocks which are called porphyry, lava, or trap.
There is a large variety of these rocks bearing difterent names according to their composition, but the ferms given are generic.
135. Where do the plutonic rocks occur?
They are found in large masses forming the backbones of all large mountain ranges and the summit of peaks of
Mining Primers.
the lesser mountains and sometimes intruding small crevices of the stratified rocks. Occasionally they occur
as exceptional layers between other sedimentary rocks. Ex clusive of the exceptions, the granite, gneiss and syenite are found below the lowest known fossiliferous strata, wherever one penetrates the crust suffi ciently to reach these depths. Or they are found underneath the upturned strata as in Fig. 8.
Granite
Fig. 17.
136. What are the granites
composed of?
Crystals of quartz, orthoclase-feldspar, and mica. The quartz is a very hard white crystal, the feldspar a very soft pink or whitish compound, while the mica occurs in black or yellow glittering flakes. The color of the feldspar determines the color of the granite.
137. Where may the volcanic rocks be seen?
They are found as extensive vertical sheets that stand boldly above the surface like massive walls called dykes (A, Fig. 18); they may be found as exten sive overflows poured out on the surface (B, Fig. 18); or as immense sheets between the strata. These are found in all regions of great disturbances — where the earth's crust had been subject to the violent lateral pressure following the cooling and burst giving vent to the molten mass of matter from the interior.
138. What are the porphyries composed of?
Mineralogically, the rocks are merely a combination
of some one of the feldspars with hornblende, or augite. One group contains a predominenceof orthoclase-feldspar, while the other contains the plagioclase- feldspar. Of the former we have Trachyte and Rhyoiite and the glassy obsidian (sometimes mistaken for Anthracite
Geology
Mining Prim Ees,
coal, sometimes for blackglass). Basalt and Doleriteare the common forms oi the latter group.
139. Can the two classes be recognized by the naked eye?
The granite rocks are usually colored and some what banded, while their crystals are intimately crushed together and mixed. The porphyries are quite characteristic with the feldspar crystals prom inently figuring in a crystal line base. They are gray or blackish in color. Some PO R PHY /? V of the more recent porphy
ries are tinted, but also Fig. 19. much finer grained. The
augite crystals are quite dark, if not black. See Figs. 17, 19 and 20.
B
Fig. 20.— Graphic Granite : a, cross-section ; B, longi tudinal-section
140. Are these, the primary rocks of the earth ? Geologists are not agreed upon this matter. Un doubtedly the granites are below all the fossiliferous strata and unquestionably the volcanic rocks are ejected
A
Geology.
from below and may come from the center of the earth. But as there has been nothing to indicate either the texture or the composition of the primary rocks, our present knowledge does not extend beyond the age of the granite (the Archaean age). They certainly represent the oldest formation known to us.
There are, however, some anomalies in the study of the granite rocks that lead geologists to the belief that they are altered or re-fused stratified rocks.
j First. They occur between other strata.
Second. Their massive conditions pass insensibly 'into metamorphic gneiss on the one hand and into volcanic rocks by slight gradation on the other.
141. Are the volcanic rocks regarded as the primary rocks ?
It can not be said of them any more than of the granites that they are the primary rocks. By the term we mean the original magma of which the earth is composed. According to the theory of a planet cooling from an incandescent fused condition Fig. 21.
Gneiss.
(as is the Sun ) to the present, there
certainly should be a substantial homogeneity in the molten mass. Whatever composition it may have, it should be the same throughout, and a sample of that mass erupted in Asia, should be the same as one taken from the lava of California or of Vesuvius. But this is not the case. We find that neither the granites nor the volcanic rocks are uniform in texture throughout the world. There is great diversity of composition.
The same being true of granitic rocks, there is a belief that both of these groups of crystalline rocks are not from the original molten mass, but come from some upper layer or sub-crust ; that these sub-layers may, like the limestones and sand stones, have been produced
Mining Primers.
by atmospheric actions explained in Q. 23; and that they are strata which have not been any where exposed at the surface.
142 Do they occur stratified?
Only one form of the granite, which we call gneiss, may be said to be stratified. It occasionally grades into a laminated condition that is called schist, which often can not be distinguished from sand clays. This variety of rock is fissile though not like slates. (See Fig. 21.)
As has been stated, the volcanic rocks may appear to be stratified but that is rather due to an intrusion which occurred after the sedimentary rocks were formed.
The varieties of volcanic or plutonic rocks do, however, have a peculiarly jointed structure as may be seen in
F g 22.
Figs. 22 and 23 which represent the columns of volcanic rock, or Fig. 21, showing the peculiar dyke volcanic material occurring along Lake Superior. Fig. 25 illus trates the natural tendency of granite to jointy struct ure, (See Q 47) and in Fig. 26 we have a sample of the jointy tendency of limestone or sandstone.
143. Are these due to the same causes?
Geology.
Joints in the stratified rock are probably the result of its shrinkage while in the act of consolidating from its sedimen tary condition, or in the granitic rocks while cooling after the high heat to which it has been sub ject. The columnar structure is doubtless equally natural to the eruptive rocks which cont- acted Fig. 23.
144. Then you regard the plu tonic and volran ic rocks as having been once molten and subsequently con solidated ?
I would not say that of the granitic rocks though the volcanic rocks were, without doubt, ejected in a molten state from vents opened, down to some atsof fires below the earth's crust or within it.
Those who do not regard the gran ites as primary rocks of the earth's crust, believe them to be plutonic or metamorphosed under the action of enormous heat and pressure. They claim that the granitic rocks are of sedimentary origin and during one period of the earth's cooling the con traction caused such pressure as to raise their tempera ture nearly to a melting point when they were altered from the condition of sediment to a crystalline state. Undoubtedly there is some granite which has been thus metamorphosed but it has been subjected te heat of all ages since the early Cambrian. When tho crushing was great and the wrinkling excessive, gneiss was produced. (See G, Fig. 27,) With a still greater shrinkage and compression, the signs of strati-
while cooling.
Fig. 24.
Mining Primers
Fig. 26
Geology.
"7
fication, if they ever existed, would be entirely de stroyed, a fusion would take place producing granite. However it is, there is no unanimity of opinion among geologists as to the genesis of granite and allied varie-
Fig. 27.
ties. You have the various views and we must hurry on to consider the influence which these rocks and the earth's violent changes have, or had, upon the occur rence of ores.
Chapter Vii.
145. How do ores occur?
In deposits which are called veins or beds. The former name indicates the metalliferous masses in the earth that crop out at the surface for perhaps miles in extent and continue down into the earth at an angle nearly vertical. Beds are those deposits which lie more or less flat.
146. How were the-e produced ?
It was said that the earth's crust has been broken and seamed in every direction. Some of these were closed up again at once, others were filled at the moment of formation with igneous matter and still others filled with mineral in a greater or less degree at once, or sub sequent to the Assuring. All of these may be called veins, but the first are called faults (Q. 38), the second class dykes, and the third class veins or beds. There is little doubt that veins are formed by pressure at right angles to the directions of the fissures. This explains why they usually occur in parallel series.
147. How were these filled ?
Some of these crevices or fissures have been filled from below, the mineral coming up in a state of fusion, in solution or in gaseous state, either derived from the molten interior of the earth or, probably, from the metal lic layers of the sub-crust. Such veins are necessarily of great depth and usually are found alongside of or near the walls of dykes of igneous matter. The copper ores of Lake Superior and elsewhere, and the silver veins of Nevada and Mexico are of this class.
Geology.
Some veins have been formed by a filtration into their creviees of mineralized solutions which may have been hot and alkaline, or not. These solutions either deposited their metallic contents into previously-formed cavities, or they attacked such rocks as were soluble and in the cavities thus formed substituted, by "metasomatic" interchange, mineral for rock. The cavities are found either entirely filled with a single mineral com pound as are the zinc mines of S. W. Missouri or Wis consin ; with an agglomeration of minerals as in New Mexico, Illinois, Nevada, or Colorado ; or with a number of minerals in layers forming a ribboned structure in the fissure-veins,or forming an onion-layed structure in the cavities. Finally, many cavities are merely cut away and stalactited, or else partially filled with mud and clay, the last substance to be deposited from the muddy waters carrying the mineral.
Other veins are also formed by an impregnation of the country rock by a mineralized solution from which was deposited some of the mineral. Some of the gold mines of Colorado are of this character as also are some lead-mines in Germany.
Finally, there are some curious exceptional veins tepresentedlby the Bull Domingo, in Utah, and the Bassick, in Colorado. When the crevices were being opened in the regions mentioned, large, long, deep rents were made of irregular shape: the walls did not break clean and smooth as is the case with the normal veins; but. fragments of the country rock fell into the crevices and filled them completely. Subsequently a mineralized solution or vapor percolated between the bowlders and the mineral thereof was deposited a- a cementing mate rial to the mass. Some veins or deposits have doubtless been formed by hot springs. The mineral then occurs in " chimneys."
148. You spoke of metasomatic interchange, what is that process?
Mining Primers.
It is a process in which a current of water dissolves the limestone, while at the same time, replacing it with mineral. It was undoubtedly the mode of forming the mineral deposits of Wisconsin, Leadville, and other re gions.
149. Where should we look for metalliferous veins ?
Exclusive of the beds of iron, (Q.72) and clay, or those of zinc and lead which are the results of a deposition from water currents carrying these in suspension, the metalliferous veins occur in regions of great disturbance and metamorphism. The disturbance is the prelimi nary action to the formation of fissures, and the necessary conditions for their subsequent filling with mineral, are similar to those under which metamorphic action takes place. Hence we may look for mineral veins in the v icinity of regions of igneous activity. The exceptions referred to may be found in or along any of the fossiliferous strata from the Silurian up. Some iron ore has been found in the lower Cambrian. Generally speaking there is no reason for the belief that only certain geologi cal formations can contain mineral deposits. This rule may apply locally, but is not of universal application. Any metamorphosed stratum may contain veins. The relative age of a vein may not be known. For example, H, of Fig. 18, was filled sometime after the Silurian age.
The Cambrian quartzites of Colorado are very rich in mineral which happens to have been deposited along the contact with the limestone above it. These are the famous "contact veins" of Leadville and Aspen, Colora do. The mineral also enters into cavities and crevices of the limestone. At 0, Fig. 18, will be noticed a con tact layer of porphyry, not o' mineral, which, however, is shown at H.
As will be explained later, the presence or proximity of a porphyry, in sheets or dykes, is a very favorable indication for mineral. Porphyry appears to be the home of the mineral and hence whenever a member of
Geology.
this class of rocks is found, we have reason to expect mineral in it or along the line of juncture with the sedimentary rocks. Fig. 28 is a portion of a vein at Leadville, which may be termed a "contact."
150. Are contact veins profitable ?
Though they are not popularly so regarded, yet there are many examples of rich contact veins. " Blanket" veins, that is, those which lie flat among the sediment ary beds and perhaps are not at any edge exposed to daylight, are as a rule not very extensive or rich. Fis sure veins are sought everywhere, particularly those with good walls, though that is only a miner's prejudice.
151. What do you mean by walls ?
When a rent is made in the rocks and the fissure opened, the faces of the crevice become the walls to the
Fig. 28.
vein when it has been filled. It is believed by miners that the two smooth walls constitute an essential feature for a strong, continuous, rich vein, but as you have seen, they are mere accidents and a perfection of walls in no wise
Mining Primers.
affects or effects, quality or quantity of the enclosed vein matter in the lode.
152. Is there any difference in meaning between lode and vein ?
No ; lode is a corruption from the verb to lead and an outcrop is the sign that leads the miner to the vein.
153. What is the difference between a deposit and a vein ?
The former is a general term defining any accumula tion of mineral, whether the shape is regular or irregular. Isolated bodies of mineral are called deposits. When the ore is quite regular and continuous we call the mass, a vein or bed.
154. Does the ore in a vein solidly fill the entire space of the fissures ?
The fissure being accidentally filled it may have ores filling the entire fissure, but that is rare. Usually the ore has mixed with it other substances which do not pay, yet must be extracted to get the precious metals. Or, the mineral may have accumulated along a thin streak of a few inches width, while the remainder is
Fig. 29.
barren quartz rock. The ore may occur only as a mass of specs dotting the rock here and there. When we
Geology.
m
read that a vein is 10 feet wide it means, therefore, not that the ore which will pay for extraction is 10 feet wide, but that the crevice, in which some ore is scatter ed, is 10 feet wide.
155. Does the crevice always maintain the same width ?
No: it " pinches and shoots," as it is called. This is easily explained. Imagine Fig. 29, a to be the original crevice made during the disturbances already described. Perhaps afterwards, further movement occurred. In such case tho two parts of the country, A and B on either side of the crevice may have shifted to the posi tion, 6, leaving the ere vice, which was subsequently tilled, to have large " pockets" for ore-shoots and small places where it is said to have " pinched" the vein.
Chapter Viii.
156. What are ore shoots?
That is a name given to the richer portions of a vein, which are of considerable extent. The term ''pockets" designates bunches of mineral.
157. What was meant by ribboned- structure and onion- layered structure in Q. 147 ?
Many of the veins in the plutonic rocks look like the illustrations in Figs. 30 to 32, where the layers on the two sides are symmetrical. These would suggest that at
A
Fig. 30. Fig. 31.
one time the layeis 1, 1, were deposited by one solu tion ; later, 2, 2 ; after which 3, 3, were formed, and so on. Or they may have all been deposited from the same solution according to their insolubility; the inner most one being that which was more soluble than 1, or
Geology.
6*5
even 4.
Beds of mineral, exhibit similar structure as in Figs. 33 and 34, which is similar to the ore occur rences in Missouri and Wisconsin. The heart is dry bone, A; the next layer is hematite, B ; the next calamine, C, etc., etc.
158. Are these common ?
Not uncommon. But as a rule, the mineral occurs in specs, streaks, or bunches, and mingled with fluor spar, quartz, or calc spar as gangue,or waste rock, on either side of which along the walls is a layer of clay called selvage, or arouge. This latter facilitates the breaking of mineral from the walls, as without it, the ore is not easily broken away free from the rock.
159. Do these metals occur in a pure state?
Very rarely. Gold is found pure in the veins — per haps 90 per cent, of the world's production being from the "native" metal. Of this quantity the portion re-
Fig. 32.
Fig. 33.
Fig. 34.
Mining Primer.
covered from the veins directly is not one- fourth of that which is obtained from the detritus of the eroded veins. Nearly three fourths of the gold production comes from placer washings. It occurs in thin wires or leaves, between slate3 or in quartz, or else in infin itesimal particles in the porphyry or quartz veins. The remaining 10 per cent, is obtained from one of the chemical compounds of gold with tellurium, etc. The gold is recovered mainly by contact with mercury (quicksilver) which absorbs it. Silver is found native, and mined, but only in a few places — Peru, Norway, and the Lake Superior region having supplied the larger portion of it. Exclusive of these, silver is obtained from various minerals. Some mines have very rich pockets or accumulations of a ruby colored mineral (of which the Granite Mountain mine is a famous illustra tion) ; in others it is found as a blackish mineral in specs or lumps, called "sulphurets" ( properly ,argentite); while in others the silver is in gray flakes, combined with copper, and called "gray copper" (tetrahedrite). By far the larger portion of the silver production of the world, comes from mines, the ore of which contains the silver sparsely disseminated through galena (a lead mineral), pyrites, (iron — , or copper — ), zinc blende (sometimes called black-jack), and spathic iron ore. The minerals may only occur in the gouge of the vein, while the vein-matter is barren of any value, or it may be collect ed in the vein-matter. Either the silver mineral is concentrated out of the mixture (see Surface A appliances) to be afterwards melted down into bullion with pure lead or copper, or else this preliminary is dispensed with and smelting resorted to at once.
Copper occurs native in the Lake Superior region, and in Arizona, from which is derived 20 per cent, of the world's production, and 50 per cent, of that of the U. S.; it is found in combination with carbonic acid, forming a beautiful blue mineral known as azurite ;
Geology.
and it also occurs as a massive green semi-precious mineral called malachite; while fully 55 per cent, of the copper is smelted out of the various sulphide com binations called pyrites, (chalcopyrite), bornite, and chalcocite. A majority of the copper mines are in fis sure veins.
Lead is mined all over the world in the form known as galena (combination of sulphur and lead).
Leadville Colorado, is, however, a mining district which produced 300,000 tons of metal from a white crystalline lead mineral, called carbonates (cerussite). This is an oxidized form of galena, resulting from ex posure to air and water. These deposits are believed to be exhausted. The veins of Leadville are flat ( in limestone and between it and quartzite). Those of Illinois, Missouri, Nevada, Wisconsin and many districts in the Old World are of similar occurrence. (See Fig ure 35.) All fissure veins in the western part of the U. S. carry galena.
Fig. 35.
There are only five minerals of iron sufficiently abundant to become ores— Hematite, Limonite, Sider-
Mining Primer.
ite, Magnetite, and Pyrites. These are found in many parts of the world, in the Silurian beds, and in the crystalline rocks.
Zinc is obtained from three minerals — zinc blende, calamine and smithsonite — which are usually con centrated after having been mined, and then heated in retorts to volatilize the zinc which is received in condensors.
Reviewing these statements, it may be said that iron ore occurs as a distinct bed and the native and carbon ate copper ores are generally free from admixture with other ores, but all of the other metals named are found in greater or less association. Thus galena and blende are almost inseparable and rarely found alone
Pyrites with silver and gold minerals are usual ac companiments to the galena in fissure veins or in de posits. The geology of one is therefore allied to that of the others. So, also is the mechanical and chemical treatment f r their recovery and extraction.
Fig. 36.
160. How much of these minerals is requisite to con stitute an ore ?
That depends upon the proximity of the mine to market, the method of mining, and the quality — that is, the character of the valueless portion of the ore. A mine very near a railroad does not require as large or as
Geology.
rich a deposit as one which is located on the top of one of the Rocky Mountain hills. On the average, how ever, an ore yielding $10 worth of gold per ton may be regarded as pay. In the Black Hills and elsewhere, $3 in gold will repay the cost of mining and treating one ton of ore, but the conditions are very favorable. In Leadville an ore yielding $25 in silver and lead may be regarded as very rich ore. In isolated communities
the ore should carry $40 to pay the cost of mining, transportation and treatment. In some localities of Europe an ore having 3 per cent, of lead and 8 ounces of silver ($7 to $10) has paid 10 per cent, dividends to the
Mining Primer.
operators. The famous Comstock bonanzas only averag ed about $80 per ton, from which must be deducted the cost of mining and treatment, the interest on the capital and the high charges for transportation. A lead and zinc ore carrying 200 lbs. of each per ton pays very handsome profits in Missouri.
Iron ores should contain not far from 50 per cent, of iron to be profitable. Their value ranges at about $3 per ton. But like all these others, often the quality of the gangue determines the marketable value of the ore.
161. In what way?
If the minerals were perfectly free from admixture with other substances, the metals sought for and obtained from their smelting would also be pure. Any foreign substance which is associated with the minerals will, in the melting, necessarily affect the quality of the product. Thus 1 lb. of phosphorus in a ton of iron ore would ruin the pig-iron obtained therefrom for any purpose except the commonest. Steel could not be made out of such iron. Likewise 3 or 4 lbs. of sulphur would render the iron containing it toe brittle. In like degree, small amounts of bismuth and antimony would injure the lead for sheets or pipes ; while the presence of pyrites in blen le would injure the quality of the zinc distilled therefrom, besides destroying the retort in which it is fired. Copper is likewise affected by the presence in it of iron or arsenic. More than this, as we learned under "Analyses of Coal, Ores, etc. ''and under "Surface Appliances," the value of silver and gold may occur in fine flaky mineral. As this can not readily be concentrated, it would, therefore, be lost. No matter how rich it may be, the larger portion of the value had better been absent than present and misleading.
The silver may be with the zinc ; in which case unless it were previously ascertained, the concentrator
Geology.
would be losing the most valuable portion of the ore. For usually, the concentrating plant is "set" for saving the lead mainly, and the zinc only incidentally. (See Q. 76, "Surface Appliances".) On the other hand the silver value may be associated with the barytes rather than the other minerals. In this case without special provision, concentration is worse than useless, and the ore has, practically, alow value. The same is true of gold. It is not uncommon for it to be of the hard quality .or rusted over with pyrites so that it will be re jected by the quicksilver which is employed for gather ing it. Even a thick bed of fine quality coal is almost valueless if there are many "brasses" or "nigger heads" in it.
162. Does the mineral character of a vein remain constant with depth?
Not always so. Some fissure veins have a galena ore at the surface ; and rich copper bornite below; in many the zinc blende disappears at a few hundred feet of depth; in others, the zinc does not occur nearer to the surface. In many mines, the free or oxidized ores near the surface, change to sul phides below. In very many di-tricts the vein matter for some distance down from the surface consists of a ' cap " of dense iron quartz below which are found the precious metals and minerals. The surface quartz of other fissure veins is honeycombed and barren, when the mineral has been washed out of the matrix by the solvent agencies, which have flowed subsequent to the deposition of the mineral. So it is evident that both the character and the value of the mineral of fissure veins may change. There existed some time ago a be lief that fissure veins were richer at great depth than at the surface. But the many deep explorations have dis proved this fallacy, as a rule of universal application.
163. Is there any prevailing direction on the surface
Mining Primers.
or with depth which is particularly favorable to rich veins?
That is only locally true. There is no direction of outcrop or dip of vein which may be said to be univers ally that of rich veins. The crevices and fractures rent in every direction were accidental and casual, (Q. 38) and in any given locality were in a direction at right angles to the pressure. As the direction of pressure was not the same all over the globe, the fissures would not be parallel. In limited regions, however, the veins are usually in parallel series. This gives rise to what is termed a "belt," by which is known a district of parallel veins carrying similar mineral. Thus a silver belt, a copper belt, and a tin belt exist in one district.
164. How is that explained ?
At one time, a certain series of crevices were opened in the earth and, at that time, or later, were filled with
Fig. 38.
tin and copper by some mineralizing agency. Subse quently there came other disturbances which broke across the country another series of fissures which were min eralized with lead and iron. When the contortions of nature again rent the rocks in a different set of veins, which became receptacles for lead, we had the first two*
Geology
vein belts intersected by this latest, or youngest, belt, Fig. 38 illustrates the appearance of the surface cut up by such disturbances as I have described . Neither the number nor the order is constant, so that the figure is merely one example of many. Fig. 39 is another example, showing the vertical arrangement and inter sections of two old veins D and C by two of more reeeni formation.
165. Are these intersections common9
Yes, and give rise to much litigation. For example, if M, Fig. 40 is a vein owned and operated by a certain
pot-tv and i- reached in the course of work by another pa rt v owning the vein N. the question naturally
arises : Which is the contin -
nation of N ; or. To whom does O belong? Do the veins intersect as in Fig. 40. or do thev drag i n Fig 41 ? Ordinarily, it is a difficult matter, unless the veins are so entirely different in
.Mining Primers.
character as to leave no 100m for doubt. If the con tents are somewhat similar, then the decision is not very easily made
166. What determines the answer?
When the veins are similar in gangue and mineral, the gouge, iQ. 1.58) may be the only guide. The presence and character of the gouge along 0 compared with
those of M and N will deter mine the identity to M or IN. The problem became ver v c o m pi e x, h o w e v e r, when the intersected vein slips, as already explained in Q. 39, and results in some such intersection as showm in Fig. 42 where the miner along N would find no vein on the other side of M and would hence follow M, until he is discovered or dis closes the continuation 0.
Fig. 41.
167. How will N be able to find the continuation of
his vein ?
By a rule which, though not infallible is almost always correct. You will notice in Fig. 39 how the veins were not only broken, but misplaced ; this is the usual result of
intersectionsand faulting.
When in driving a gallery a cross course is en countered its strike and pitch must be noted. Then the miner should cut through it to the other side, for the continuation of the vein on which he is driving may not be displaced. If it is dislo cated, follow this rule.
1. When the cross course (be it a vein, a dyke or only a slip) dips a way from you, the continuation
Geology.
of the vein is on the side opposite to the direction in which the vein pitches.
2. When t! e cross course dips toward you then the continuation is on your right or left accordingas to whether your vein dips to the right or left.
168. Please give an example.'
Suppose you were following a vein which dips downward towTard the left hand. You meet a fault ing plane. Drift through it to the far wall. Now7 drive a prospecting gallery to the right along the far wall, if you found the fault dipping away from you.
If your gallery encountered an intersecting vein that pitched tow7ard you (if the floor of t tie gal lery meets the fault, first) then after reaching the far side of the vein you would drift along that to the left The explanation for this simple rule
is too elaborate for re cital here. Fig. 43 is a plan of the mine ac cording with this last instance. The arrows indicate the direction of the dip. The grained portion is the excess in width of the vein over the gallery.
169. How far would one have to go ?
That can not be given as a general rule. The average distance of the displace ment of several thousand mineral-veins is about 16 feet. The amount of the throw varies with the intensity of the action and perhaps the time that has elapsed since the fracture.
170. Why do you drift along the far w all ?
Mining Primers.
Because one is then in "country rock" and can readily distinguish the vein -matter the latter is met. This would not be so easy if the gallery were driven in the faulting vein.
171. Is there any change in value or amount of min eral at the points of intersection ?
That is still a debated point. I would say from my experience and reading that the places of inter sections of two metalliferous veins are usually richer in quantity than are other points of either vein. Drags. Fig. 41, are not often richer than adjacent portions.
172. Does the direction ortheamountof the dip appear to have had any influence upon the richness of the vein 9
Only locally, as explained in Q. 163. Tn a certain locality onlv the veins which dip to the West carry any valuable mineral while the intersecting series having a Southward dip are of poor grade. Not 20 miles away are three districts in all of which the South dipping veins are the only ones mined, not one of those dippins' Northward being of any present value. There are no West dipping veins. In Fig. 39 all of the four veins are quite valuable. 0 being very rich, and A having had three extensive pockets of high grade ore.
Finally a very singular case of rich vein, is crudely illustrated in Fig. 44. A large fissure had been formed at some period of the earth's history, but instead of being a clean break which was subsequently filled as shown in b lgs. 30 to 34, the break was a, very irregular one and the filling followed immediately after the fracture with fragments and boulders of the country rock that had been shattered by the forces. Soon a mineral impreg-
Fiu. 44.
Geology
nation took placeand the angular masses were cemented together by rich mineral which filled the interstices between the boulders. There are only two such mines known to the writer.
The Correspondence School Of Mines.
The curriculum of the school covers the whole art of Coal and Metal Mining and the sciences related thereto.
The Complete Mining Scholarship.
This Scholarship embraces Instruction in the following subjects:
Arithmetic, Ventilation, Geology, Search for Coal, Modes of Working Coal and Metal Mines, Surveying Coal and Metal Mines, Mine Machinery, Ambulance, Mining Legislation, Mine Accounts.
Price: $35.00 payable in advance, $40.00 payable in installments.
The Mine Mechanical Scholarship.
This Scholarship embraces Instruction in the following subjects:
Arithmetic, Mechanics, Machine Design, Strength of Materials, Boilers, Engines, Hoisting and Haulage Ap pliances, Pumps, Applications of Compressed Air, Me chanical Ventilators, Mining and Drilling Machines, Mine Surface Arrangements, Practical Geometry", Me chanical Drawing.
Price: $25.00 payable in advance, $30.00 payable in installments.
The Metal Prospectors' Scholarship.
This Scholarship embraces Instruction in the following subjects:
Blowpiping, Mineralogy, assaying, Economic Ge ology, Prospecting. Price: $20.00, payable in advance.
The Full Scholarship.
This Scholarship includes all the subjects taught by the School in the other Scholarships.
Price: $50.00 payable in advance, $55.00 payable in installments. Students holding the Metal Prospectors' Scholarship can take The Complete Mining Scholarship by paying $30 additional,
Or, The Mine Mechanical .Scholarship by paying $20 additional, Or, The Full Scholarship by paying $35 additional.
For Particulars and Circular of Information, apply to
The Correspondence School Of Mines,
Scranton, Pa., U. S. A.
The Correspondence School Of Mechanics.
(Conducted on the same principles as The Correspondence School of Mines.) Supplies a complete education in Arithmetic, Geometry and Trigonometry, Elementary Mechanics, Hydraulics, Pneumatics and Heat, Mechanical Drawing, Applied Mechanics, .Strength of Materials, Machine Design, Boilers and Engines, Electricity. This School was instituted to meet the wants of Engine Drivers, Ma chinists, Shop Foremen, Firemen, Pumpmen, and others connected with machinery. The practicability of the system of instruction is evidenced by its great popularity. The complete Mechanical 'Scholarship embraceall of the subjects given above. Price: $35 payable in advance, $40 payable in installments. A separate course, embracing the subjects of Arithmetic, Geometry and Trigonometry, Elementary Mechanics, Hydraulics, Pneumatics and Heat, and Mechanical Drawing. Price; $25, payable in advance. For par ticulars and circular of information, apply to
The Correspondence School Of Mechanics,
Scranton, Pa., U. S. A.