Gold Belt of the Southern States. Shaded portion shows area of Crystalline Schists. (From Trans. Am, Inst, Min. Engrs.) The ore-bodies which have been mostly worked are found in the mica-schist formations or formations with a garnetiferous, semicrystalline character. They are low-grade deposits, but of such size as to warrant successful exploitation in many instances. The two mines which have been successfully operated on the narrow high-grade veins are the Creighton and Walker. The ore is as a rule very refractory, being usually associated with graphitic slate and graphite, through which the gold has been disseminated. Other ore is intermixed with talcoid micaceous schist. In both cases but a very small part of the gold is free-milling. The so-called "saprolites" of this district consist of decomposed schist or gneiss. At the surface the gold is practically all free-milling, but with depth when the undecomposed sulphides are encountered, the ratio of free-gold to that held in the sulphides is about one to three.' The Arbacoochee district, Cleburne County, contains the more important mines. An area of nearly 100 acres is known to be auriferous in the Clear Creek Valley consisting principally of placer diggings, but later quartz-veins and pockets have been opened up. The deposits being very irregular and pockety, their value can only be determined by more or less extensive development work. An ore known as "goober pea" is found in the Arbacoochee district, which is characterized by a peculiar speckled appearance being really a conglomerate of quartz and slate nodules cemented together with talc and stained with iron. This ore is moderately soft, and is not difficult to amalgamate. The ore of the Mossback mine averages $25 to $30 per ton, and is free-milling. It occurs in a decomposed vein-filling of sandstone and slate cut by quartz stringers. The mines of most importance in this county are the Lucky Joe, on Turkey Heaven Mountain, the Annie Howe, Price, Red Rover, Eckles, Lee, Crown Point, Sutherland, Middle Brook, Bennie Field, Ballinger, Gold Eagle and Moss Back. In Randolph County is only one mine of prominence, the Pinetuckey, which stands among the first in the state, and really belongs to the Arbacoochee district owing to its proximity to it. The vein has a north and south strike, with a dip of 20 degrees east. The average thickness is from eight to nine inches. The quartz is highly vitreous and of bluish color. It is said that about one-half of the gold is free-milling, the remainder being in sulphurets. T. A. I. M. E., Vol. 26, p. 466. Fed. Inst. Min. Engrs., Vol. 14, p. 93. The veins lie more or less conformably in a very garnetiferous, hornblende-schist as a country-rock. At a depth of 60 feet the vein has been cut off or turned to one side by a mass of light-colored granite, which was located by prospect drilling. The Idaho district of Clay County has two mines of some importance, namely, the Idaho and California. The Idaho mine ore-body is composed of quartz stringers intersecting decomposed hornblende and mica-schists, with well defined walls. The mine is more in the nature of a quarry having but little underground workings, the formation being taken out en masse for fully fifty feet. Alaska. As has been pointed out, the auriferous impregnation of this territory must have been strong and wide spread as is evidenced by the universal occurrence of gold both in the free state and in pyrites, often high in value-further, gold values in the tundra, creeks, gulches and benches attest its wide distribution. Aside from the alluvial deposits, gold is found for the most part in small quartz-veins and stringers which occur in metamorphic rocks. Then too there are mineralized zones of these rocks, where the gangue material is largely wanting. Iron pyrite is not only the most common associate of gold in the parent rock, but occurs in the largest quantity. Gold occurs both in the free state and combined with pyrites, forming sulphurets. Quartz and calcite are the common gangues, while biotite, sericite and chlorite are less common. The minerals and metals associated with the gold are native copper, copper pyrites, galena, mis pickel, pyrrhotite, siderite, silver, pyrargyrite and blende. There are three broad belts in Alaska in which the principal goldbearing deposits are found. The most important one parallels the Pacific coast line traversing the narrow strip of territory known as the "Panhandle" and terminates among the islands of southwestern Alaska. In this zone are practically all of the quartz mines of the territory and some small placer deposits. Another belt extends northward from the international boundary, near the Klondike, and includes a large part of the country lying between the Yukon and the Tanana, and probably turns to the southwest, entering the region drained by the Kantishna. Only placer gold is produced in this belt. The third belt is of the least importance, owing, probably, to its not being well known. It includes the placer district of the upper Koyukuk. However, the placers of the Kobuk River and Seward Peninsula may represent the southwesterly extension of this belt. Only placer gold has been obtained with the exception of a single quartz mine on Seward Peninsula.1 Probably the most important belt of gold-bearing quartz-veins yet discovered occurs along the southeastern coast. It has been worked at Berner's Bay, Douglas Island, Juneau, Silver Bow Basin and Cook's Inlet, of which the deposits on Douglas Island are of prime importance. The veins occur in Tertiary rocks, slates, schists and granites and carry free-gold and auriferous pyrite. Veins in igneous rocks have been found on the Skwentna and the Kuskokwim, as well as in the Tordrillo Mountains. The golddeposits here are associated with intrusions of Eocene age. Further, gold-silver veins of considerable importance are found on Unga Island.2 Following directly upon the discovery of placer mines on Douglas Island the Paris claim, which site was subsequently occupied by a large surface pit or "Glory hole," was purchased by John Treadwill. On tracing the ore-body eastward the Mexican mine was located. The deposit as opened up was the upper or "feather edge" of an intrusion of sodium syenite or albite diorite, having been decomposed and silicified by solfataric or hydrothermal action, bringing about concentration of native gold and auriferous pyrites in sufficient quantities to make its extraction profitable. The larger part of the country-rock is a carbonaceous slate of quite uniform texture, the origin of which was sedimentary. Later came the intrusion of syenite which formed an extremely irregular shaped dike. In the Alaska-Treadwell mine the dike is 420 feet wide, at the Mexican 150 feet and at the Ready Bullion it has again increased to 300 feet; these figures, however, include large horses, and in places a system of parallel slate divisions. Following the intrusion of syenite came another of gabbro on the hanging-wall side, which is several hundred feet wide, and is considered to have been of prime importance in the formation of the Following this in turn and extending over a considerable period of time, there occurred the mineralizing processes acting upon the syenite, and the ultimate deposition of the ore. There was still another intrusion, but consisting of basalt, with a width of from four to six feet. It cut through slate, syenite and gabbro, and badly shattered the country-rock, the resulting openings being later filled with auriferous material. However, the basalt 1 U. S. G. S., Bull. No. 284, p. 5, 1905. T. A. I. M. E., Vol. 33, p. 812, 1903. does not contain ore as no subsequent action has broken or fissured it forming receptacles for the deposition of ores. The ores may be grouped into two classes: first, stringers of quartz and calcite filling fissures in the syenite; and second, a breccia, as it were, of syenite fragments and associated minerals which accompanied the auriferous solutions. According to Professor Adams the ore is a mass of fractured rock filled with veinlets, and he says: "It may, therefore, be stated that the ore of the Treadwell mine is a granite, probably belonging to the class of the hornblende granites, much crushed, altered and impregnated with secondary quartz, calcite, and pyrite; that the kernels' are portions of the rock in which alteration is less complete than in the mass of the granite, and that at least a considerable portion of the gold present in the ore is contained in the pyrite as free-gold." 2 The gangue minerals of the Alaska-Treadwell mines are comparatively rare being chiefly quartz and calcite. In the impregnated portions the carbonates are usually found in larger quantities than the quartz. Of the metalliferous minerals pyrite is by far the most common. Chalcopyrite occurs more frequently in the Treadwell than in the Mexican mine, while mispickel occurs in the Mexican, but not in the Treadwell mine. Galena, blende and pyrrhotite are not common but are fairly uniformly distributed.3 Other deposits on Douglas Island are found in Silver Bow Basin, Sheep Creek Basin, Sumdum Bay, Berner's Bay, Funters Bay and Nyak Bay. The county-rock of the Silver Bow Basin consists of micaceous schists of sedimentary origin the strike is north, 60 degrees west, and dips about 60 degrees to the northeast. The rocks are cut by several nearly vertical dikes of about six feet width. Quartz often occurs in large quantities besides being a gangue associated with calcite. The metalliferous minerals are siderite, pyrite, mispickel, galena and blende. The ore sent to mills is worth about $4 to $5 per ton. In Sheep Creek Basin the Silver Queen mine is of the most importance, and has been developed to a greater extent than the others. The rocks are carbonaceous and micaceous schists which are cut by dikes of gabbro similar to the Treadwell deposits. However, the gabbro is here a decomposed greenstone. The vein has a maximum 1 Mines and Minerals, Vol. 24, p. 251. U. S. G. S., 18th Ann. Rept., Pt. 3, p. 65, 1896-97. |