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Powellite is very similar to the mineral Scheelite, though it is much rarer. It forms a series with that mineral, and contains tungsten in place of the molybdenum. Powellite often forms as an alteration product of Molybdenite, sometimes only partially replacings it. Powellite is named after geologist John Wesley Powell (1834–1902), a director for the United States Geological Survey. |
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Chemical Formula |
CaMoO4 |
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Composition |
Calcium molybdate, often with some tungsten
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| Variable Formula |
Ca(Mo,W)O4 |
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Color |
White, beige, light yellow, light brown, orange, light blue, green |
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Streak |
White |
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Hardness |
3.5 - 4 |
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Crystal System |
Tetragonal |
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Crystal Forms
and Aggregates |
As small dipyramidal or pseudo-octahedral crystals, often with striations and sometimes with triangular growth layers. Also
encrusting, grainy, and massive. May also form as an alteration product of Molybdenite assuming the original hexagonal or foliated shape.
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Transparency |
Transparent to translucent |
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Specific Gravity |
4.2 |
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Luster |
Adamantine |
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Cleavage |
3,1;2,1 |
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Fracture |
Conchoidal to uneven |
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Tenacity |
Brittle |
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Other ID Marks |
Strong yellow fluorescence. |
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In Group |
Tungstates and Molybdates |
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Striking Features |
Crystal habits and fluorescence. |
| Environment |
In hydrothermal replacement deposits as a secondary mineral in molybdenum deposits, and in basalt traprock deposits and granite pegmatites.
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| Rock Type |
Igneous, Metamorphic |
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Popularity (1-4)
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3 |
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Prevalence (1-3)
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3 |
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Demand (1-3) |
2 |
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Powellite is as a rare and expensive collectors mineral.
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Powellite is not a common mineral. It forms as a replacement mineral in molybdenum deposits, and its identity in these cases is frequently undetected (though it can easily be observed by its fluorescence). The largest single crystals, which are also of excellent form and highly aesthetic, come from the Indian traprock deposits of Nasik and Jalgaon, in Maharashtra state. A green, copper-rich Powellite comes from the Jardinera No. 1 Mine, in the Atacama Region of Chile. In the U.S., light green Powellite came from the Carlota Mine, Top of the World, Globe-Miami District, Gila Co., Arizona; and Molybdenite replacements from the Goodall Farm, Sanford, York County, Maine.
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Scheelite - Fluoresces bright bluish-white, whereas Powellite fluoresces yellow.
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Have a question about Powellite? Visit our Q&A Community and ask the experts!
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