The Emma Bell chromite deposit in Siskiyou County, California contains over 5 million tons of dunite averaging about 4 percent Cr2O3. Chromite is not evenly disseminated throughout the dunite, however. For the most part the deposit consists of many chromite-rich bands in sharp contact with, and separated by, common dunite containing 1 to 2 percent accessory chromite. Electron microprobe and petrographic analysis of accessory chromite shows that it is fine grained (average grain size 0.14 mm), generally lower in Cr2O3, and has a lower Cr/Fe ratio than segregated chromite. In addition, unusual patchy zoning is exhibited by some accessory chromite. These patchy zones are extremely rich in iron (>60 percent total iron oxide).
The negative factors such as the fine-grained nature of the accessory chromite and high iron content compared to segregated chromite, could be overcome by the very large tonnage in the deposit.
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The Emma Bell Deposit, Siskiyou Co., California : a possible low-grade source of chromite