Round Valley Mine

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United States Department of the Interior, Geological Survey Bulletin 922-Q, 1941, ppgs. 512 & 513 : The Round Valley Mine, which has been the most productive in the pendant, contains three ore bodies developed by three adits, a glory hole and an incline shaft 65 feet deep beneath the glory hole. Each of the ore beds has been productive, but the western one, mined through the glory hole, has provided the main tonnage. This body, 100 feet long and 20 feet wide, dips 45 degrees west. Workings at the bottom of the incline shaft contain no commercial ore along the downward extension of this body although ore, now being extracted through the shaft, is still present in the bottom of the glory hole. Part of the ore in the glory hole consisted largely of phlogopite mica with quartz.

The second, central ore bed, composed of tactite ore, has been crosscut by an extension of the adit beneath the glory hole as well as by a shorter adit farther east. Part of the body has been stoped from the upper adit, but the same bed in the lower adit is of too low grade to be productive.

The third, east bed, is not connected with other workings. A large underground stope in this bed, still open, was never extended to the surface. Ore remaining in the chutes and in the pillars contains large scheelite crystals in tactite composed mainly of hornblende, pyroxene and garnet.

Still further east and extending across the pendant are other thick tactite beds that may contain scheelite.

Although the scheelite content of each ore bed has decreased in depth, there seems to be no valid geological reason why other bunches of ore should not be found still deeper, for the pendant and favorable beds extend downward probably several hundred feet.

No ore has been found on the southern contact of the pendant with the granite, and there has been very little prospecting along it. There may be undiscovered ore along this contact, though the absence of faulting along the contact may have prevented the passage of tungsten-bearing solutions.

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