Geology and Ore Deposits of Boise Basin, Idaho by Anderson Alfred

Author:Anderson, Alfred
Language: eng
Format: epub, pdf
Published: 1947-03-25T05:00:00+00:00

high-grade ore accompanied by much ore of lower grade, but, as accurate sampling in advance of mining and milling has been done at but few mines, the average tenor of the ore is known in only a few places. Systematic sampling was carried on in recent years at the Gold Hill mine, and the mill records show that the ore from the different ore bodies contained from less than 0.3 to as much as 0.5 ounce in gold and small amounts of silver to the ton. Some of the ore was sorted underground, but much of the material hoisted consisted of altered rock with thin ore seams, which individually were very rich but were mixed with sufficient broken rock to maintain a mill feed of fairly constant value. Much of the ore milled at the Mountain Chief mine apparently contained from 0.5 to 1.0 ounce of gold to the ton, but the actual tenor varied considerably and was probably in part considerably less. The Belshazzar ore was reported to average 0.5 ounce to the ton, but rich pockets in places increased the gold content to several ounces to the ton. Systematic sampling at the Mayflower mine during the early half of 1938 showed much ore with 0.5 to 1.0 ounce in gold to the ton and in places pockets with several ounces to the ton. Ore with as little as 0.15 ounce in gold to the ton was being milled.- No sampling was done at the Comeback mine, but only the rich ore seams were selected, sorted, and shipped to the smelters. In general these shipments netted several hundred dollars to the ton in both gold and silver.

The tenor of the base-metal ore is also variable and depends not only on the abundance and distribution of the base-metal sulfides but also on the presence and sporadic distribution of the precious-metal seams. Smelter returns on three cars of ore from the Silver Gem lode in 1919 were reported by the operator to have contained 0.2 ounce of gold and 80 ounces of silver to the ton, 6 percent of copper, 3.5 percent of lead, and 6 percent of zinc. Two carload lots from the Coon Dog No. 1 claim in 1916 contained according to Jones 56 0.12 ounce of gold and 14 ounces of silver to the ton, 5.2 percent of copper, and 7.1 percent of zinc, whereas sampling on another lode showed 0.1 ounce of gold and 11 ounces of silver to the ton and 12 percent of copper. Ballard also reports an assay of 0.1 ounce of gold and 19.5 ounces of silver to the ton, 16 percent of lead, 13.2 percent of zinc, and 10.8 percent of copper. 57 Smelter returns shown the writer on mill shipments made from the Enterprise group in 1930 showed a range of 1.4 to 3.13 ounces of gold and 10.0 to 15.6 ounces of

66 Jones, E. L., Jr., Lode mining in the Quartzburg and Grimes Pass porphyry belt, Boise Basin, Idaho : U.

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