The High Grade district is in northeastern Modoc County near the California-Oregon border. The district is on the crest of the Warner Mountains about 10 miles northwest of Fort Bidwell and 50 miles northeast of Alturas. It was known as the Hoag district until 1912.
This region was first settled in the 1850s. Several Indian wars were fought in the area, and Fort Bidwell was a U.S. Cavalry post from 1865 to 1892. According to local legend a prospector named Hoag found gold in the Warner Mountains northwest of the fort. However, he was killed by Indians soon after his discovery. Modoc County has a recorded gold production from 1880 to 1885, which may have come from this district.
Gold was rediscovered by a sheepherder in the Warner Mountains in 1905. A boom lasted for a few years, and as many as several hundred men were employed in the mines. Intermittent prospecting and development work continued through the 1920s and 1930s, and there has been minor work since. It is doubtful if the district has yielded more than several hundred thousand dollars worth of gold.
Geology and Ore Deposits
The rocks in the main part of the district consist of white to yellow rhyolite of Tertiary age. To the west and south is andesite, and to the east is basalt, both of Miocene age. The ore deposits consist of narrow, north- and northwest-trending epithermal veins and replacements in rhyolite. The vein material consists of quartz, silicified and brecciated country rock, and fault gouge. The ore contains free gold, finely divided pyrite, and manganese-stained material. A few veins in andesite contain minor amounts of copper. None of the deposits extends to a depth of more than a few hundred feet.
Blue Bell, Fort Bidwell Cons., Klondike, Modoc, Northern Star, Sunset, Sunshine.
Averill, C. V., 1929, Modoc County, gold: California Div. Mines Rept. 2S, pp. 10-19.
Averill. C. V., 1936, Modoc County, High-Grade district: California Div. Mines Rept. 32, pp. 448-451.
Gay, T. E., Jr., and Aune, Q.A., 1958, Alturas sheet: California Div. Mines, geologic map of California.
Hilt, James M., 1915, High-Grade district: U. S. Geol. Survey Bull. 594.
Tucker, W.A., 1919, Modoc County, High Grade mining district: California Min. Bur. Rept. 15, pp. 241-250.