and teeth of the elephant have been found imbedded in them. The gravel is composed of such rocks only as are found to the eastward in the foothills and the mountains of the Sierra Nevada, and consequently must have come from that general direction. A section of the gravel occurring in the New Kelly claim shows the deposit to consist of: I. Top soil (red sand) II. Coarse red gravel with sand (the gravel is chiefly granite) III. Red cement hard-pan.. IV. White sandy clay.. V. Red cement hard-pan.. VI. Sand and pebbles.... VII. Loose yellowish sand. VIII. Dark-colored gravel of granite, slate, porphyry, Total..... Quartz gravel of large size is of rare occurrence. Boulders of diorite, several tons in weight, are common in some of the deeper holes of the bed-rock. The greater part of the gold is confined to the lower stratum of gravel, next to the bed-rock, and is associated with magnetic iron and platinum. CHAPTER IV. THE DISTRIBUTION OF GOLD IN DEPOSITS AND THE VALUE OF DIFFERENT STRATA. No absolutely satisfactory explanation has yet been given of the distribution of gold in deposits. * The opinion is held by some that the precious metal is uniformly disseminated throughout the beds. But this is the case only in very exceptional instances, and the unequal distribution of the gold + is so general as to have given rise in California to the expression "pay dirt," which means the stratum or strata containing gold in amounts which render work profitable. Top Gravel sometimes pays.—In a few instances the gold occurs in comparatively large amounts in thin streaks of cemented gravel scattered here and there in the alluvions, and in some shallow banks it is quite generally disseminated. Even in high banks the upper portion or "top gravel," when consisting of fine light quartz-wash with no boulders or pipe-clay, and where the cost of hydraulicking is very small (owing to the facilities of a heavy grade, sufficient dump, and cheap water), has been washed at a profit, though carrying an insignificant amount of gold per cubic yard. For this reason the miner always tests the whole of the deposit. *See "The Auriferous Gravels of the Sierra Nevada of California," p. 516. By J. D. Whitney. On the subject of the relative position of gold in deposits see Report of Mr. Stutchbury, Government Geologist of New South Wales; Quarterly Jour. Geol. Soc. 1858, p. 583, M. A. Selwin; "Gold-Fields and Mineral Districts of Victoria," pp. 81, 82, 87, 131, 173, R. Brough Smythe; Cotta's " Lehre v. d. Erzlagerstätten," vol. i. p. 101, and vol. ii. p. 556; Murchison's "Russia and the Ural Mts.," vol. i. pp. 482-487, and "Siluria," p. 456; Whitney's "Auriferous Gravels of the Sierra Nevada," p. 361; J. Grimm's "Lagerstätten d. Nutzbaren Mineralien," p. 26; Hartt's" Geol. and Phys. Geog. of Brazil," pp. 50, 51, 159, 160; Mawe's Travels, pp. 222-227; Munroe's “Mineral Wealth of Japan," Trans. Amer. Inst. of Mining Engineers, vol. v. p. 236; “Gold Deposits of Jaragua,” Ann. d. Mines, 1817, vol. ii. p. 202. See" Gold-Fields and Mineral Districts of Victoria," p. 84. The top gravel of the channel which passes through Columbia Hill, Nevada County, has in several instances been successfully washed. This is especially remarkable on account of the great depth of this deposit, which, from the explorations on Badger Hill and Grizzly Hill, is inferred to be from six hundred to six hundred and twenty feet deep. Gold in the Grass-Roots.--Not unfrequently a fine lamina gold is found in the grass-roots. This last mentioned circumstance is in no way localized, the same fact having been noted in other countries. Mawe called attention to the existence of gold in the grass-roots on Mount San Antonio,* in Brazil; and Walsh states that gold was first discovered in the deposits between San José and San João, Brazil, by Paulistas, who, pulling tufts of grass, "found numerous particles of gold entangled in the roots." + Pay Gravel sometimes high above Bed-Rock. -At the Polar Star Mine, Indiana Hill, Placer County, the best pay was found from six to eighty feet above bedrock. At diggings near Forest Hill, Placer County, the gravel twenty to sixty feet above the bed-rock has yielded profits. At Bath a stratum one hundred feet above bedrock was drifted profitably and the top dirt hydraulicked subsequently. Pay Gravel generally near Bed-Rock. But experience has proved that, as an almost universal rule, the top gravel of deep alluvions is not rich enough to warrant large investments of capital. Also that the "pay " is obtained, not from the washings of the entire bank, but chiefly from that stratum or those strata which are in most cases within eight or ten feet of the bed-rock. Where this is of slate upturned on its edges the gold frequently permeates it one or two feet.‡ Mawe's Travels, p. 264. + Walsh's Notices of Brazil," 1828-29, vol. ii. p. 122. + See Murchison's Siluria," p. 456, and “Russia and the Ural Mountains," vol. i. p. 487; also "Gold-Fields and Mineral Districts of Victoria," pp. 86, 106. Tuolumne River Claims. The gold alluvions found near and along the banks of the Tuolumne River, Stanislaus County, present some striking examples of the distribution of the precious metal. The pay dirt in the Chesnau claim is confined to within six feet of the bedrock. In the Sicard claim, six hundred feet south of the iast and across a ravine, with banks twenty to forty feet high, the gold is disseminated more generally so long as there are no sand strata; but whenever the latter appear the pay is confined to near the bed-rock. In the Patricksville Light claim the pay stratum is six or seven feet thick and adjoins the bed-rock. The gold is concentrated in this layer so long as there are sand strata in the bank, but with their disappearance it becomes more diffused throughout the detritus. At the French Hill claim the pay was limited almost exclusively to the gravel near the bed-rock. Nevada County.-The bulk of the pay dirt in the cement gravel in Nevada County is within thirty feet of the bottom. In drift claims the workings are nearly always confined to within a few feet of the bed of the channel. Sand generally poorer than Gravel.-In the gold-bearing drift of the Sierra Nevada layers consisting exclusively of wash-sand are generally found to contain very little if any of the precious metal. Rich Pay in Undulations and Depressions.At French Hill, Stanislaus County, where the bed-rock was undulating, and in depressions found around a little hill formed by a sudden rise in the bed-rock, the gravel paid better than in any other portion of the claim. The gold-fields south of Miask,* in the Ural Mountains, present a similar case, all the undulating ground and depressions around conical hills being the most productive of gold. At the Patricksville Light claim a large hole in the "Russia and the Ural Mountains," vol i. p. 83 bed-rock, twenty five feet deep, was bottomed. The hole was filled with gravel, but no pay was obtained. The pay stratum was found to be on a level with, and a continuation of, the pay stratum of the rest of the claim. On the other hand, at the Chesnau and French Hill claims whenever these hollows are found a large yield of gold is invariably obtained. The experience of miners in the gold-fields of Victoria has led to the conclusion that "in large auriferous rivers gold is always found on the bars or points, and not in the deep pools or bends." In substantiation of this are cited Reid's Creek, Woolshed, Twist's Fall, Yackandanah near Osborne's Flat, and Rowdy Flat; at each of these places large holes were cleaned out and only a few colors obtained, while shallow flats immediately below them were very rich.* In gulch-mining it sometimes happens that from the position of the bed-rock the detrital accumulations assume the form of reclining cones, the apex reposing upon the top of the hill. Where such is the case the bulk of the gold is concentrated in the lower end of the deposit. These gulches are frequently found to be exceedingly rich. These facts are cited merely as an explanatory outline of the subject, and to show why a system of sluicing should be adopted which bottoms the entire deposit. EXAMPLES OF THE COMPARATIVE VALUES OF THE DIFFERENT GRAVEL STRATA. North Bloomfield.-To ascertain the comparative value of the gravel strata at Malakoff, Nevada County, on the ground of the North Bloomfield Mining Company, a series of tests was made of the dirt extracted from a shaft sunk, two hundred and seven feet deep, in the channel. The first one hundred and twenty feet from the surface "Gold-Fields and Mineral Districts of Victoria," p. 134. |