This district is in east-central Placer County at the site of the old town of Damascus, about seven miles southeast of Dutch Flat. It includes the lode mines of the Pioneer-Humbug Bar area on the north and the extensive placer deposits that extend from Damascus south through Forks House to the Sunny South-Gas Hill area.
The streams in this area were originally mined during the gold rush, and drift mining began in the late 1850s. The Hidden Treasure drift mine was discovered in 1875 and was worked on a major scale through the early 1900s. There was some mining activity in the district again during the 1930s, and there has been intermittent prospecting since. This area has been quite productive; the drift mines alone have had a total output of more than $12 million and the lode mines several million dollars more.
An early Tertiary gravel channel extends from Damascus south to Gas Hill and eventually southwest to Michigan Bluff. An intervoleanic channel that apparently eroded away portions of the earlier channel enters the area from Wesrville to the east. The lower earlier "white" channel is more than 300 feet wide. It contains abundant quartz. The gravels in this early channel yielded 50 cents to $1.75 per ton at the old price, and the gold was coarse. The upper channels are commonly known as "blue" channels. Bedrock is slate and schist, and the gravels are capped by rhyolite and andesite. The channel has been mined by drifting almost continuously from Damascus south to Hidden Treasure, a distance of more than four miles. The quartz veins, which occur in slate, range from two to eight feet in thickness and contain free gold and often abundant sulfides. The are usually is low to moderate in grade, but the ore shoots had stoping lengths of up to several hundred feet. The Pioneer mine was developed to a depth of 1400 feet.
Lode: American Eagle, Black Hawk, Central, Dover, Floyd, Lynn, Mars, North Star, Pioneer $1 million, Rawhide $300,000+, Southern Cross.
Placer: Bullion, Cameron, Comet, Gas Hill, Golden River, Hermit, Hidden Treasure $4 million, Mountain Chief $700,000+, Mountain Gate, Rainbow, Tickell.
Browne, Ross E., 1890, The ancient rivers of the Forest Hill Divide: California Min. Bur. Rept. 10, pp. 435-465.
Crawford, J. J., 1894, Golden River and Hidden Treasure mines: California Min. Bur. Rept. 12, pp. 208-210.
Logan, C. A., 1936, Gold mines of Placer County, Hidden Treasure mine: California Div. Mines Rept. 32, pp. 65-66.
Lindgren, Waldemar, 1900, Colfax folio, California: U. S. Geol. Survey Geol. Atlas of the U. S., folio 66, 10 pp.
Lindgren, Waldemar, 1911, Tertiary gravels of the Sierra Nevada: U.S. Geol. Survey Prof. Paper 73, pp. 150-159.
Waring, C. A., 1919, Placer County, Damascus district and Placer County drift mines: California Min. Bur. Rept. 15, pp. 317 and 352-375.