The Orogrande district is in T. 27 N., R. 7 E., about 12 miles southwest of Elk City.
Lode mines were developed in the late 1890's; however, the largest mines, the Orogrande-Frisco and the Gnome, were not productive until 1902 and 1932 respectively (Shenon and Reed, 1934, p. 52). The Gnome produced 11,582 ounces of gold from 1932 to 1937, when it was closed (Lorain, 1938, p. 44). The district produced small quantities of gold annually through 1957 and through 1959 its total was 32,000 ounces; almost all production was from lodes.
Country rock in the Orogrande district consists of quartz monzonite and granodiorite of the Idaho batholith and schist of the Belt Series (Shenon and Reed, 1934, p. 30, 31, pi. 1). The ore deposits are of two types: gold-pyrite disseminated through a silicified shear zone in the schist, and small veins and stringers of quartz and sulfides in granodiorite and dacite. The dacite intruded the granodiorite and the mineralization is related to the dacite. Ore minerals consist of pyrite, chalcopyrite, galena, tet-radymite, molybdenite, native gold, gold telluride, wolframite, and scheelite.
SIMPSON-CAMP HOWARD-RIGGINS DISTRICT
The Simpson-Camp Howard-Riggins placer district, in Tps. 24 to 28 N., R. 1 E., along the Salmon River between Riggins and Freedom, has been intermittently productive since the 1860's. Most of the activity immediately followed the initial discoveries; from 1862 to 1866 an estimated $575,000 in gold was produced (S. M. Barton, M. W. Wells, and E. Oberllig, written commun., 1958). In the 1930's, large-scale but unsuccessful mining methods were introduced (Lorain and Metzger, 1938, p. 80). The district, which was still active in 1959, produced a total of 9,578 ounces of gold from 1903 through 1959.
The placer deposits are in bench and stream gravels. The bench gravels, which have been more productive (Lorain and Metzger, 1938, p. 82-85), occur along the main stream canyon as much as several hundred feet above present stream level. The stream gravels consist of small bars along the present river course.
The Tenmile district is between lat 45Â° 33' and 45Â°55' N. and long 115Â°31' and 115Â°44' W., immediately north of the Buffalo Hump district and west of the Elk City district.
Both placer and lode deposits were worked in this district, but the placers were more productive. Gold was discovered in 1861 in Newsome basin in the gravels of Newsome Creek. Most of the gravels were soon exhausted, but they yielded approximately $2 million (about 100,000 ounces) in gold (Ross, 1941, p. 61). Lode properties were developed as early as 1888 (Lorain, 1938, p. 30), and they emerged in recent years as the more important sources of gold. The lode mines produced an estimated minimum of 18,400 ounces of gold to about 1932 (Shenon and Reed, 1934, p. 71-82). From 1932 through 1959 the district produced 28,671 ounces. Total estimated gold production was about 147,000 ounces.
Bedrock in the area consists of gneiss and quart-zite of the Belt Series and granodiorite and quartz monzonite of the Idaho batholith. The granitic rocks intrude the gneiss. The ore deposits are in quartz veins that fill fractures and faults in gneiss, quartz monzonite, and quartzite. Variable amounts of the sulfides, pyrite, chalcopyrite, arsenopyrite, chalcocite, galena, covellite, and sphalerite occur in the veins, and gold is associated with the sulfides (Shenon and Reed, 1934, p. 71-82).
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