The Auriferous Gravels of North Carolina
"The Auriferous Gravels of North Carolina" is an article from Proceedings of the American Philosophical Society, Volume 19 . View more articles from…
Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.
Stop
Early Journal Content on JSTOR, Free to Anyone in the World
This article is one of nearly 500,000 scholarly works digitized and made freely available to everyone in the world by JSTOR.
Known as the Early Journal Content, this set of works include research articles, news, letters, and other writings published in more than 200 of the oldest leading academic journals. The works date from the mid-seventeenth to the early twentieth centuries.
We encourage people to read and share the Early Journal Content openly and to tell others that this resource exists. People may post this content online or redistribute in any way for non-commercial purposes.
Read more about Early Journal Content at ://about.jstor.org/participate-jstor/individuals/early- journal-content .
JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people discover, use, and build upon a wide range of content through a powerful research and teaching platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not-for-profit organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please contact support@jstor.org.
188I.J 477 [Chance.
appeared to be gray copper was pulverized as a whole, and analyzed with, the following result :
Calculated
Sb 10.10
Sb 2 S 3
13.68 :
; 340 — 0.0403
Bi 5.05
Bi 2 S 3
6.59
: 513 0.0138 I
Cu 14.97
Cu 2 S
17.01
: 136 0.1076 ] : 339 0.0169 !
Pb 3.84
PbS
4.04
Ag 0.70
ZnS
3.84 :
: 97 0.0396
Zn 3.56
Ag 2 S
0.80
: 348 0.0033 j
Fe 1.33
(Cuj Fe) S 2
4.03
S 11.53
Quartz, etc.
48.55
Insoluble 48.55
If the gray substance be considered homogeneous then its molecular ratio will be
But gray copper has the ratio of 4 : 1. If the bismuth sulphide be now eliminated with the corresponding positive sulphide in the Alaskaite ratio of 1 : 1, then we get for the ratio of the rest
RS : Sb a Sj 3.86 : 1 that is nearly the gray copper ratio.
It is made even more probable that such a mixture be here in existence, by qualitative tests upon a large specimen, weighing several kilograms of the massive gray mineral. These tests indicated very varying percentages, by the intensity of bismuth reaction from different points of the piece.
It is a matter of remark from a genetic point of view, that we find in this vein nests of Alaskaite quite free from the gray copper, while the latter seems to be mixed generally with the former in other places when- ever it predominates.
The Auriferous Gravels of Forth Carolina. By H. M. Chance, M.D. (Bead before the American BhUosophical Society, July 15, 1881.)
The belt of auriferous gravel stretching in an almost unbroken line from the New England States to Alabama, is broadest in North Carolina, where it has also been more productive in the past, and promises greater results in the future than in any other State through which it passes.
Yet notwithstanding the flattering prospects apparently presented by these gold fields, the companies organized to work them have rarely at-
Chance. 1 47o [July i5 f
tained practical success even for a short period ; they have, in fact, almost without exception, failed to pay dividends, and their stock is now a drug in the market.
But a period of excitement has again been inaugurated, capitalists are again investing in mines long since abandoned as unremunerative, and old Californian miners are leaving the West for the more glittering pros- pects of the East, where they say the gravel is much richer.
While making an examination of mineral lands in Central and Western North Carolina, I recently noted a series of facts that may explain in general why these fields have not been remuneratively productive in late years, although the gravel does contain a larger average amount of gold per cubic yard than many Western placers now profitably worked .
When one inquires why the workings are not financially successful, he is immediately met with the statement that the mines paid handsomely prior to the California excitement in '49, when the Western gold fever caused a suspension of operations ; that the civil war caused a second stoppage ; and that there are many reasons why they have not been systematically worked since the war.
These statements are honestly made, and are to some extent true ; but from 1855 to 1860, several companies were working, and with very dis- couraging results, and since the war several mining operations have been commenced, but discontinued — because they were not remunerative. It cannot be claimed that these operations were unsuccessful because they were not prosecuted for a sufficiently long period, for in placer workings, the results, if any, are quickly attained.
The early workings, prior to the California discoveries, were undoubt- edly remunerative. They were confined principally to the gravel de- posits found along the smaller streams, and their tributaries, notably on the First and Second Broad rivers, and on Silver and Muddy creeks in Rutherford, Burke and McDowell counties. The gravel was worked by panning, by the rocker and "long-torn," and it is also claimed at one place at least, by sluicing with a head of water.*
A brief review of the geological peculiarities of the region will explain the great difference between these old workings, and the gravels now being washed.
In the Geology of North Carolina by Prof. W. C. Kerr, page 156, the gold gravels are referred to the Champlain period, and are described as beds of till or decomposed rock {initial drift), sometimes in place, some- times several hundred feet lower on the hillside than the rocks from which they were derived by disintegration.
The truth of this statement is apparent to every careful observer, and this view is now generally accepted among those practically engaged in work- ing these deposits.
The gold seems to be irregularly distributed through the so-called "slates " (mica schist, micaceous gneiss, hornblende, schist, etc.), either in
*The first use of this method Is generally credited to California,
1881.] 479 [Chance.
thin quartz veins or disseminated through the mass. As erosion pro- gresses, the decomposed schist is converted into gravel, the lighter and finer particles of clay, mica, etc., being easily washed out by the percola- tion of rain water, leaving the heavier minerals and the larger quartz fragments behind. Thus an essentially concentrating process is and has been constantly progressive since the Glacial period, and the gravel now found lying as a surface covering from one to thirty feet thick may, and probably does, represent several times its thickness of rock, the coarser and heavier fragments of which alone remain.
The thickness of the gravel in the South Mountain region probably averages from six to nine feet, but I consider that this represents the re- mains of at least twenty or thirty feet of rock. On this basis the gravel should contain more than three times as much gold as an equal bulk of the mother rock — it is, in fact, found to be much richer.
The streams draining this region have carried away millions of cubic yards of this gravel. The old river bed workings in California have shown that all streams act as natural sluices, separating and concentrating the gold and heavier minerals from rocks of less specific gravity, and this action has undoubtedly been operative in these North Carolina streams. The gravel washed into the smaller stream beds dropped its coarser gold before being carried out into the main water courses, and we consequently find that the rich washings were nearly all found in the beds of the small creeks and their tributaries.
These were thoroughly worked over during the early mining excite- ment, prior to the exodus in '49, yielding to hand panning and to work with the rocker and long-tom, from two to ten dollars a day . They have since been reworked ; at some places the same gravel has been washed three or four times. It was very rich, necessarily so, for working a stream down to bed-rock* is like cleaning up a sluice — it contained the gold dropped from millions of cubic yards of gravel, the accumulation {concen- trates) of thousands of years.
There are a few localities where these stream gravels are as yet undis- turbed. They will yield good returns, but their area is very small.
The vast bulk of gravel now remaining to be worked is hill gravel ; its thickness will not exceed an average of nine feet, and it is of varying de- grees of richness.
On some tracts gravel may be found yielding from one to ten colors to the pan, and work done with a rocker may show from five grains to a pennyweight to the cubic yard, a most flattening prospect to the Western hydraulic miner ; but such results are rare. I am inclined to think that five or six grains to the cubic yard is as much as can be expected from an average run of fair gravel.
The important question, now being solved in a practical way on the
The bed-rock was usually not more than two or three feet beneath water level.
Chance.l 4o" r j a i y 15(
ground, is : Can these deposits be profitably worked by hydraulic mining 1 The question may be answered both in the affirmative and in the negative. At a few places where the gravel is both rich and thick — ten feet or more — and water can be obtained in sufficient quantity at moderate cost, hydraulic mining may be successful— but
1. A large working area is necessary.
2. The closest economy must be exercised, and
3. A relatively small amount of capital invested.
A large area is necessary, because the deposit is not thick ; assuming an average thickness of four yards, one acre would yield but 19,360 cubic yards of gravel, and one-fourth of this being top gravel and soil might contain very little gold, as the gold is often concentrated in the lower layers, sometimes in a "pay-streak," near the bed-rock. This "pay- streak " is at times quite thin — one, two or three feet thick, but the gold is more usually disseminated through the mass.
The difference between the cost of working these thin deposits, and the enormously thick gravels of California and Oregon will be readily ap- preciated by the hydraulic engineer, and to this difference is due the fact that although these gravels are much richer than many Western deposits successfully worked, the prospect of remunerative mining in this region is much less.
In some localities the cost of bringing water will be very great; ditches ten or twelve miles long being necessary. At the Sam Christian mine, on the Yadkin river, arrangements are even being made to pump the water I
It will also be difficult to obtain sufficient fall to carry off the tailings, for some of the richest of the hill gravels has been found in comparatively low ground, where much of the material must be moved by hand. I noted one mine working under just such conditions, that was yielding as well as the best can be expected to average. The gravel was about four yards thick,' the gold occurring principally in a pay-streak near the bed- rock. The lowermost four or five feet was moved by hand, some pick work being required.
The cost for labor was about 64 cents per superficial square yard, and the yield averaged over a considerable area one pennyweight — 85 cents. Labor 75 cents per day. This shows a profit of 21 cents per superficial square yard or 5.25 cents per cubic yard ; but these figures do not include the cost of superintendence, mercury, wear and tear, etc. When these items are included, it can easily be seen that the operations were being carried on at an actual loss, for not more than one hundred yards were washed per diem, and the profit on this would not pay the expenses of management.
A trial of General Strong's injector dredging machine* is now being made on the gravels in the bed of Silver creek. It seems better adapted to working on river bottoms than on these small South Mountain streams.
Described by Dr. R. "W. Raymond, in Vol. viii, Transactions of the American Institute of Mining Engineers.
1881.] 481 [Chance.
I have reason to think from what I have seen, that there are compara- tively few localities where these North Carolina hill gravels can be suc- cessfully worked at present ; that in any event the returns — considering the risk — will be small; that no "bonanza" need be expected, though local deposits of very rich gravel will undoubtedly be found ; and that no operations can be successful unless the strictest economy is observed in all the details both of management and working.
Stated Meeting, July 15, 1881.
Present, 4 members.
Vice-President, Dr. LeConte, in the Chair.
A letter acknowledging the receipt of certificate of member- ship was received from Ast. Eoy. G. B. Airy, dated Eoyal Observatory, Greenwich, June 18, 1881.
Acknowledgments of the receipt of Proceedings were re- ceived from the Smithsonian Institution (boxes of 302 addresses for distribution; and 108); the Prag Observatory (104, 105, 106; List); E. Danish S. S. (105, 106; List); Ver- mont Historical Society (107); Mus. C. Z. Harvard Collection (108); A. Agassiz (108); T. P. James (108); New Bedford Public Library (108); United States Military Academy (108); Poughkeepsie S. N. S. (108); J. J. Stevenson (108); Buffalo S. N. S. (108); F. A. March, Easton, Pa. (108); Chicago His- torical Society (108); and State Historical Society, Wisconsin (108).
Donations for the Library were received from the New Zealand Institute; the Danish Society of Sciences; Accademia dei Lincei; Ee vista Euskara; Society C. Geog., Bordeaux; Geographical Society, Paris; Mus.N. H., Paris; Eoyal Belgian Academy; Eoyal Astronomical Society and Meteor. Com. London; Boston N. H. S.; American Oriental Society; Har-