Blackbird Mining District, Lemhi County, Idaho, USAi

Regional Level Types
Blackbird Mining District	Mining District
Lemhi County	County
Idaho	State
USA	Country

The Blackbird District, located in the Panther Creek drainage, is bound on the northeast by the Mackinaw District, on the southeast by the Eureka District, and on the southwest by the Yellowjacket and Gravel Range Districts. The Musgrove Creek drainage is sometimes considered to be the Musgrove Mining District; however, here it is considered to be part of the Blackbird.

The first mining claims in the district, located during 1893, were for gold. The presence of cobalt was not recognized until 1901 (Umpleby, 1913, p. 160). Precious metal mineralization appears to be concentrated in a small area near the lower part of Musgrove Creek. The Musgrove mine, located prior to 1900, developed a zone of fme-grained, brecciated quartzite containing pods of quartz, calcite, siderite, pyrite, pyrrhotite, chalcopyrite, bieberite, and malachite (Roberts, 1951). The mine produced significant amounts of gold and silver between 1913 and 1914 (USBM production records). The ore was processed in a 17 ton per day cyanide concentrator (Gerry, 1914, p. 776 and 1916, p. 624).

At the Breccia Gold mine, a gold- and silver-bearing fault breccia zone occurs along the contact between argillaceous rocks of the Yellowjacket Formation and Challis Volcanics. According to Grove (1985, p. 5), several thousand tons of ore were mined during the late 1930's and 1940's.

An open pit was developed at the site during 1987 by Metro Resources and 4,600 tons of ore were shipped for test milling. Resources are 5 million tons grading 0.138 to 0.140 ounce gold per ton (Grove, 1985).

The Blackbird District is best known for its world-class copper-cobalt deposits. The deposits are stratabound in fine-grained clastic, volcaniclastic, and tuffaceous rocks of the Middle Proterozoic Yellowjacket Formation. At the Blackbird mine, five stratabound zones, the Idaho, Dandy, Chicago, Brown Bear, and Blacktail, were mined. Ore minerals in the zones consist chiefly of cobaltite, chalcopyrite, pyrite, and lesser amounts of safflorite, arsenopyrite, pyrrhotite, linnaeite, native gold and silver, enargite, sphalerite, and galena (Nash and Hahn, 1986, p. 1-10).

The Blackbird mine produced ore intermittently from both underground and surface workings between 1902 and 1968. Ore produced during the mines's heyday, the 1950's and 1960's, was processed in a 1,000 ton per day flotation mill constructed by Calera Mining Company during the early 1950's. Vhay (1964b, p. 70) and Bergendahl (1964, p. 100) reported that 63 million pounds of copper and 14,000 ounces of gold have been recovered from the Blackbird Mining District, mainly from the Blackbird mine. According to USBM files, the Blackbird mine has produced 13,865,496 pounds of cobalt, 53,450,171 pounds of copper, 24,136 ounces of gold, and 53,544 ounces of silver from 283,741 tons of ore between 1939 and 1968.

The Blackbird mine and surrounding area contains the largest known reserve of cobalt ore in the United States (Bilbrey, 1962). Published reserves total about 6.5 million tons grading 0.55 percent cobalt and 1.31 percent copper (Bennett, 1977, p. 42).

Recent drilling at the Sunshine prospect, located west of the Blackbird mine, has identified a reserve of 300,000 tons grading 0.69 percent cobalt, 1 percent copper, and 0.024 ounce gold per ton. Additional resources at the Sunshine include 2,250,000 tons at approximately the same grade (P. Nisbet, Formation Capital Corp., personal communication, 3/10/97).

At the Blackpine mine, near the southeast end of the Blackbird copper-cobalt zone, recent drilling has also identified copper-cobalt-gold resources. They contain 3 million tons grading 0.5 percent recoverable copper, 1 million tons averaging 4.5 percent copper, 0.08 percent cobalt, and 0.03 ounce gold per ton, and 400,000 tons grading 1 percent cobalt and 0.1 ounce gold per ton (P. Nisbet, Formation Capital Corp., personal communication, 3/10/97).