By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Placers were discovered in Boise County in 1862 about 25 miles northeast of Boise in Boise Basin, an area of about 300 square miles. The placer operations led to the discoveries of lodes at the heads of streams, and some of these lodes were mined as early as 1863 (Anderson, 1947, p. 176). The lodes were never developed to sustain any extended yield; first one district would be active for a few years, then another. Placers, on the other hand, had a less erratic history and remained highly productive through the 1890's. In the early 1900's they were worked by dredges, and some time later, by large-scale hydraulicking (Ballard, 1924, p. 31-32).
The Boise Basin is divided into many mining districts. In this report that part of the basin that includes the Idaho City, Moore Creek, Gambrinus, and Centerville camps is referred to as the Boise Basin district. The Pioneerville (Summit Flat, Grimes Pass) and Quartzburg (Gold Hill, Granite, Placerville) districts are considered separately.
In general, bedrock in the mineralized parts of Boise County consists of quartz dioritic and quartz monzonitic facies of the Idaho batholith, which are cut by groups of porphyry dikes of Tertiary age. Certain areas are covered by Tertiary lake beds, by basalt lavas of the Columbia River Basalt of Miocene age, or by Quaternary alluvial deposits (Anderson, 1947, p. 129).
Recorded production in the county began in 1863 (Jones, 1917, p. 86). Total gold production for the county from 1863 through 1959 was 2,891,530 ounces, about 95 percent of which came from the Boise Basin.
Boise Basin District
The Boise Basin (Idaho City, Moore Creek, Gambrinus, Centerville) district is in the central and southern part of the Boise Basin.
All the districts in the Boise Basin have a common history related to the original placer discoveries in 1862 and subsequent development of both placer and lode gold mines. The first placer discoveries in Boise County were made in this area in 1862. Most of the county's gold production came from the rich placers during the first few years of mining. Estimated production from 1863 to 1896 from the Idaho City camp was valued at $44,651,-800 (2,167,500 ounces) (Lindgren, 1898, p. 655). The district produced 129,038 ounces from 1939 through 1958; its total production was about 2,300,000 ounces, mostly from placers.
Lode mines in the Gambrinus area were active from time to time. Two of the most productive were the Illinois and Gambrinus with outputs valued at $225,000 and $263,000 respectively (Lindgren, 1898, p. 685-686).
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