Claim, in Green Valley Gorge and near Damascus. Between these two extremes there are many variations. At Indiana Hill and Smith's Point furrows and channels have been cut in the bed-rock. Pot-holes occasionally occur, and in some cases yield considerable gold. Crevices also occur in the bed-rock, and are usually rich in gold, even more so than the gravels. The gravels are both cemented and uncemented, and are often interstratified with sands and pipe clay. The quartz gravel and boulders are quite variable in amount, the latter often attaining considerable size and usually near bed-rock. Occurrences of lenticular masses of clay, more or less consolidated, and of a chocolate-brown color, and varying from nothing to five feet in thickness, are occasionally met in the gravels, being locally known as "chocolate." The finer gravels or pebbles consist of quartz and metamorphic rocks, while angular fragments of igneous rocks often lie on or close to bed-rock. The thickness of the volcanic capping ranges from a few hundred to a thousand feet, and consists of black and white lava and volcanic ash and breccia. The channels vary in width from a few feet up to 100 and occasionally to 600 feet.1 At Mokelumne Hill, Calaveras County, the gravels are thin, but very rich. They have a capping of some 200 feet of sedimentary volcanic material. The gravel is fine-grained and homogeneous, but somewhat variable in character. Above the gravel is a layer of angular andesitic boulders.2 The gravel deposit of Dutch Flat, Tuolumne County, consists of coarse gravel with many boulders five to six feet in diameter. The lower gravel is usually blue, owing, it is claimed, to the big slate boulders. Above the blue gravel is a red gravel consisting largely of red and white quartz. The gold in the blue is coarser than that in the red gravel, the latter being flat and scaly and often fine.3 The so-called seam-diggings consist of decomposed bed-rock filled with seams and stringers of gold. Such deposits occur at the Illinois Cañon, Georgia Slide, Young's Dry Diggings, the Spanish Dry Diggings, etc. This material is not unlike the saprolite of the Southern Appalachian gold fields, and similar occurrences in Alaska. The country-rock is slate and sandstone which in some cases, as in the Spanish Dry Diggings, is filled with pyrites and traversed by 1 Auriferous Gravels of the Sierra Nevada of California, pp. 89–112. ' Ibid., p. 128. Ibid., p. 151. numerous quartz-seams. Occasionally the deposits are very pockety pinching out when the quartz-seams run into hard rock.1 Colorado. In Colorado, as elsewhere, auriferous gravels were the first form of mines worked, and through their exploitation many of the veins were discovered. Among the first placers discovered and worked were those on Chicago Creek, just above the junction of Clear Creek. These deposits were known as the "Deadwood Diggings" and yielded considerable gold. Further, the decomposed rock or surface ores of veins (which might possibly be called saprolite) were sluiced to some extent. These placers were worked to the best advantage and profitably between 1859 and 1863. In the Idaho Springs district, as elsewhere in the state, auriferous gravels may be grouped into three classes, namely: River bars, stream gravels and bench deposits. The river gravels and bars lie in or adjacent to the stream beds and consist of gravels, sands and boulders lying on the bed-rock and forming the bed of the streams. The bench deposits are in most cases remnants of ancient river beds, and have probably been added to by wash and slides from the mountain sides above. They have for convenience been divided into three classes: first, those 25 feet above the present stream level consisting largely of glacial material worked over by the present stream; second, gravel terraces situated some 55 feet above the beds of the creeks and, as has been suggested, are possibly of preglacial origin; and third, other deposits fully 180 feet above the stream channels, being composed of indurated river gravels probably of late Tertiary origin. The elevations given here are for the Idaho Springs deposits, and will vary somewhat with other locations. These deposits were in certain places remarkably rich, the best values being found either in the deep gravels in the channels or directly on bed-rock. Mining was carried on here by tunnels and shafts, in this respect following the California practice.2 On the south side of Hahns Peak gravel bars have been worked in two places, namely; Ways Gulch and Poverty Bar. These gravels are probably reconcentrations from the conglomerate underlying the Red Beds, which are loosely consolidated." The placer deposits of Leadville furnished the bulk of the gold and were the principal source of the precious metals prior to the dis 1 Gold, Its Occurrence and Extraction, A. G. Lock, pp. 142-144 and Auriferous Gravels of the Sierra Nevada of California p. 115. 2 U. S. G. S., Bul. 285, p. 36. 9 U. S. G. S., Bull. 285, p. 31. covery of silver. California Gulch was probably of the most importance, while the Iowa and Evans gulches adjoining it on either side and containing more extensive deposits have yielded comparatively little gold. The bend of the California Gulch below Oro, at the Mouth of Nugget Gulch, was probably the richest portion, the next in point of yield was the bend at the La Plata mine, while the next in importance was below Graham Gulch. The gulch gold varied from $17 to $19 in value per ounce, while that from the veins averaged about $15.1 The Fourmile placers are situated about 75 miles south of Rawlins in Routt County, Colorado, and Carbon counties, Wyoming, on the Snake River. They cover an area of some 1200 square miles and range from 2 to 20 feet thick, average probably nine feet. The gravels occur on the uplands or mesas, the bed-rock having an elevation of 100 to 150 feet above the valley. As a rule the gravel is free from cement, pipe clay or boulders and is readily broken down and washed. The gold is quite uniformly distributed throughout the gravel and is easily saved. It is claimed that the yield of the gravel is 20 cents and upwards per cubic yard. The principal creeks in the district which yield gold are: Fourmile, Timberlake, Thornburgh, Dry Gulch, Scandinavian and Big Hole. Gold is also found for a distance of ten miles along the Snake River, beginning south of Big Hole Creek." occurs. At Fairplay and for some distance below, the bed-rock in places is fully 35 feet below the stream bed, showing a depth of deposit of 100 feet. About ten miles from Fairplay are the Alma placer workings. Here the bed-rock is a coarse sandstone known as Weber-grit, upon and in the crevices of which most of the gold To save the gold often several feet of bed-rock are removed. The gravels vary from 50 to 75 feet in thickness being made up of sand, gravel and boulders, the latter of porphyry and of a considerable range in size. Besides the porphyry, granite and quartzites are present in varying quantities. The gold varies in size from dust to quite coarse grains and nuggets, the former extending even to the grass-roots.3 On Swan River are the Fuller placer mines. There are three forks of the Swan River, namely; the North, South and Middle forks the South Fork is in a country of porphyritic overflow and carries gold, while the Middle and North forks are barren of gold, U. S. G. S., Monograph No. 12, p. 515. the former lying wholly in slates and sandstones, the latter has its source in a granite-country. The gold-bearing gulches of this district are: the Georgia, Brewery, Brown, French, Mayo, Illinois, Boston, Dry and Negro. The first or Georgia Gulch was worked as early as 1859. Some placer-mining has been done at Cripple Creek and vicinity, but owing to the peculiar condition of the gold which has been derived from the oxidation of tellurides, being light and powdery or spongy, no very rich placers have been formed. Limited operations have been conducted at Hull City, along Beaver Creek, in Squaw Gulch, Arequa Gulch and on Wilson Creek. Gophering has been attempted on the southern slope of Mineral Hill, the gravels being washed in rockers, and dry-washing has also been tried.1 The Carolinas. There are two gold-bearing districts or belts in the Carolinas and Georgia, namely: the western goldfield of North and South Carolina and Georgia, and the field of central North Carolina and Georgia. The former being close to the Blue Ridge lies in the highlands where the valleys are deep. The gravels being nearer their source are coarser and, as a rule, the deposits are more abundant and thicker than in the central field. The following streams cross the gold-belt in their downward course from the Blue Ridge; the Catawba, Etowah, Chestatee, Yahoola and Cane Creeks. These streams and their branches are auriferous and as they have cut downward have left hill-deposits and old channels filled with gravel.2 The character of the auriferous deposits which are worked as placers in these states are similar to those of Alabama, consisting of gravels and saprolites. (See Alabama). Small scale placer-mining has been carried on in various parts of North Carolina. At the Portis mine, Franklin County, auriferous saprolites are worked by surface-sluicing and hydraulicing to a depth of 15 to 30 feet. The country-rock is diorite which is intersected by quartz-stringers. The Sam Christian mine near Troy is a gravel deposit varying in thickness from one to three feet. The gold was mostly coarse and many nuggets weighing from 5 to 1000 pennyweight were obtained. The Crawford mine, Stanley County, is a true gravel deposit in which the gold is coarse and nuggety. The bed-rock is slate upon which lie angular fragments of quartz and country-rock in a clay matrix, 1 U. S. G. S., Professional Paper No. 54, p. 152, 1906. 'T. A. I. M. E., Vol. 25, p. 798, 1895. U. S. G. S. 16th Ann. Rept., Pt. 3, pp. 289-293, 1894-95. and is often spoken of as cement. The nuggets show but little wear, being rough and irregular. Hydraulicing has been carried on at the Parker mine, at New London, for a number of years. The gold is coarse and nuggety. Auriferous saprolites are also worked here by a combination sluicing and milling process. Placer-mining has also been the principal source of the gold from Burke, McDowell and Rutherford counties.1 The auriferous gravel deposits are often spoken of as grits being composed of loose beds of disintegrated veins, the gravel being both rounded and angular. The origin of these deposits is recent time, even the present. They vary in thickness from a few inches to many feet and vary fully as much in richness as in thickness.2 Small scale placer workings have been carried on at various points. throughout the state and the first work done at the Haile mine consisted of branch washing, later changing to open-cutting and still later to underground mining. The gold from Spartanburg, Greenville, and Pickens counties comes largely from placers.3 According to Tuomey the gold occurs in South Carolina in "deposit" or "branch" and "vein" mines; the former having been formed at two different times or periods. The first constitute the most extensive mines of the state and consist of much worn pebbles and gravel none of which is much larger than six inches in diameter and has undoubtedly been transported from a great distance as it cannot be traced to its source. Such deposits are found in the Tomassic Valley, on the Tyger near the summit of Blue Ridge, at the foot of Poor Mountain and at Rankin's, on Little River. The second and more recent deposits consist largely of angular fragments of quartz which can be readily traced to their source in the veins in the neighborhood. In fact most of the veins were found by following up the placer deposits. Such deposits have proved remunerative at Estatoe, in Abbeville; on Lawson's Fork, in Spartanburg; and in Cherokee Valley. The gold, especially the larger pieces, is somewhat water-worn and is purer than the vein-gold." Georgia. (For distribution of gold-fields see the Carolinas.) Surface washing of gold began in Georgia and North Carolina in 1829, and extended from the Rappahannock River, in Virginia, to the Coosa, in Alabama. Gold occurs in this state as elsewhere in the 1 T. A. I. M. E., Vol. 25, pp. 693-717 and Ibid. Vol. 25, p. 728. 2 Gold, Its Occurrence and Extraction, A. G. Lock, p. 155, 1882. T. A. I. M. E., Vol. 25, pp. 717-718. Gold, Its Occurrence and Extraction, A. G. Lock, pp. 154-159, 1882. |