The Juneau district includes Douglas and Admiralty Islands, lat 57Â°00' to 59Â°00' N. and long 133Â°00' to 135Â°00' W.
Placer discoveries were made in 1869 at Wind-ham Bay and at Sumdum Bay, about 50 miles south of Juneau, and lode gold, which has been the mainstay of the district, was discovered in 1880 by Joe Juneau and Richard Harris whose locations included the site of the Alaska Juneau mine, the largest lode gold mine in Alaska (Wright, 1906, p. 2). The discovery resulted in a rush to the area and the founding of the town of Juneau, which, by 1883, became the locus of gold mining in Alaska. Numerous lode properties were located near Juneau and on neighboring Douglas Island where the Treadwell groupâ€” including the Treadwell, Mexican, Ready Bullion, and 700 Foot minesâ€”was quickly developed into a major producer, yielding $26,556,470 in gold through 1905. Caving, which began in the Treadwell and 700 Foot mines as early as 1913, culminated with the complete flooding of the Treadwell, 700 Foot, and Mexican mines in 1917 (Eakin, 1918a, p. 78-79). These mines were never reopened, but the Ready Bullion remained productive until 1922 (Brooks and Capps, 1924, p. 24). Other important mines in the early days of this camp were the Sumdum and Ebner. Production records for the Alaska Juneau mine began in 1893 and are complete to April 9, 1944, when the mine was closed due to manpower shortages and excessive costs (C. W. Henderson and R. V. Cushman, in U.S. Bureau of Mines, 1945, p. 232). This mine yielded a total of 2,874,361 ounces of gold, almost as much silver, and large quantities of lead. The closing of the Alaska Juneau mine signaled the end of gold mining in Southeastern Alaska. Only a few hundred ounces of gold were produced annually from the entire region from 1944 through 1959.
Total gold production of the Juneau district from 1882 through 1959 was 6,883,556 ouncesâ€”66,279 ounces from placers, the remainder from lodes.
The eastern part of the district is underlain by the dioritic and granitic intrusives composing the Coast Range batholith of Late Jurassic or Early Cretaceous age (Buddington and Chapin, 1929, p. 173-175). This is flanked on the west by several north-trending bands of schist, slate, and greenstone (Spencer, 1906, p. 16-19) which according to Buddington and Chapin (1929, p. 73-74) may include rocks ranging in age from Ordovician to Cretaceous. Still farther west is a band of inter-bedded slate and graywacke with some greenstone which Buddington and Chapin (1929, p. 157) consider Jurassic or Cretaceous. The rocks have been folded into a northwest-trending synclinorium, bounded on the east by the Coast Range batholith and on the west by an anticlinorium (Buddington and Chapin, 1929, p. 289-290).
The gold deposits of the Juneau district, according to Spencer (1906, p. 22-24), are of three types: veins, impregnated deposits, and combinations of these two types, or mixed deposits. Though other rock types may be mineralized, most of the deposits are found in the slate and greenstone. The veins vary considerably in thickness, trend, and continuity. Quartz is the main constituent; however, calcite is common, and albite is abundant in some veins. Pyrite, galena, sphalerite, and arsenopyrite are the common sulfides. Gold is either associated with pyrite or arsenopyrite or is found as small flakes in the quartz (Spencer, 1906, p. 33-36). In the impregnated deposits, the country rock has been replaced by large masses of the sulfides listed above, but these deposits are relatively unimportant as a source of gold. The mixed deposits were the most important of the three types at the famous Treadwell mines (Spencer, 1906, p. 24).
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