Baker County Oregon Gold Production
By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
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Production data for Baker County before 1880 were not found. From 1880 to 1899, the county produced $8,958,073 (about 434,850 ounces) in gold (Lindgren, 1901, p. 573). From 1904 through 1957, it produced 747,548 ounces of lode gold, 402,490 ounces of placer gold, and 11,626 ounces unidentified as to source. Total recorded gold production through 1959 was about 1,596,500 ounces; from 1954 through 1959 only a few hundred ounces was produced.
Placer mining revived after 1912, and after World War II it was more productive than lode mining. Most of the county's gold production in recent years was from the Sumpter district placer mines, which were closed in 1955.
Lode deposits of Baker County generally are fissure veins that are related to intrusions of granitic, dioritic, and gabbroic rocks (Lindgren, 1901, p. 614). The deposits most commonly are found near contacts of these intrusive rocks with sedimentary or metasedimentary rocks.
BAKER DISTRICT
Production in the Baker district has been chiefly from the placers in Griffin Gulch but this was in the early years and was unrecorded. After 1900 more than half of the gold produced in the district came from lode mines. Production of gold from 1906 through 1959 was 19,825 ounces from lode mines, 10,890 ounces from placers, and 5,437 ounces undif-ferentiated—a total of 36,152 ounces.
The oldest rocks of the district are greenstone, phyllite, quartz schist, and limestone composing the Burnt River Schist of probable pre-Carboniferous age (Gilluly, 1937, p. 9-13) and the Elkhorn Ridge Argillite, composed of argillite, tuff, lava, chert, and greenstone, of Permian and Triassic age (Bostwick and Koch, 1962). An unconformity separates these rocks from the superjacent Tertiary andesite and basalt flows. The pre-Tertiary rocks are thrown into strong folds that strike west, but the Tertiary rocks are only gently warped (Gilluly, 1937, p. 8).
The lode deposits are fissure and replacement veins in the pre-Tertiary rocks (Gilluly, 1937, p. 92). Gold, pyrite, chalcopyrite, sphalerite, and locally stibnite and galena occur in a gangue of quartz, sericite, carbonate, and a little clay and scheelite.
Placers have been worked in nearly all the gulches on the south end of Elkhorn Ridge, on Marble Creek, and on Salmon Creek. The most important placers were in Blue Canyon near Auburn, where some of the early discoveries were made.