Powellite is a molybdenum-bearing member of the scheelite group, most easily recognized by its vibrant yellow fluorescence under short-wave ultraviolet light. Collectors look for its characteristic tetragonal bipyramidal crystals, which are typically found as pseudomorphs after molybdenite or as vug linings in basaltic rocks.
Is this powellite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch powellite with a known reference. Powellite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Powellite leaves a light yellow streak.
- 3Read the lusterHold the specimen under a strong light. Powellite typically shows a subadamantine to resinous to pearly luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, greenish-yellow, white, gray.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: bipyramidal crystals, granular, massive.
Often confused with
Powellite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Scheelite is the harder of the two (Mohs 4.5-5 vs. 3.5); streak differs, so Powellite leaves light yellow, Scheelite leaves white; luster reads subadamantine to resinous to pearly on Powellite and vitreous on Scheelite.
How to tell apart: Streak differs, so Powellite leaves light yellow, Wulfenite leaves white; luster reads subadamantine to resinous to pearly on Powellite and resinous to subadamantine to adamantine on Wulfenite.
Often found alongside powellite
Minerals reported to co-occur with powellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMoO₄
- Mohs hardness
- 3.5
- Density
- 4.2-4.5 g/cm³
- Streak
- Light Yellow
- Luster
- Subadamantine to Resinous to Pearly
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Bipyramidal Crystals, Granular, Massive
- Cleavage
- Distinct On {101}
- Fluorescence
- Bright Yellow Under SW UV
- Rarity
- Uncommon
- Uses
- Collector, Indicator Mineral
- Host rock
- Oxidized Zones of Molybdenum-bearing Hydrothermal Deposits and Basalt Cavities
Where rockhounds find powellite
Classic worldwide localities
- Needles, California, USA
- Krushev Dol, Bulgaria
- Moctezuma, Sonora, Mexico
- Maharashtra, India
Field-hunting tip
Look in oxidized zones of molybdenum-bearing hydrothermal deposits and basalt cavities country, the host setting where powellite typically forms. If you start seeing molybdenite, calcite, apophyllite in float, you are in the right ground. Field specimens usually show a bipyramidal crystals, granular, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find powellite on the map
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