Cuprotungstite is a secondary mineral typically found as earthy crusts or granular masses within the oxidation zones of tungsten deposits. It is most often identified by its distinct pistachio-green color and its intimate association with primary scheelite and secondary tungstite.
Is this cuprotungstite?
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 cuprotungstite with a known reference. Cuprotungstite sits at Mohs 4-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: greenish gray to greenish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, waxy, earthy.
- 4Match the color rangeCompare against the expected color range: brown green, olive green, yellowish green.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: crystalline, massive.
Often confused with
Cuprotungstite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cuprotungstite leaves greenish gray to greenish yellow, Scheelite leaves white.
How to tell apart: Cuprotungstite is noticeably harder (Mohs 4-5 vs. 2.5); streak differs, so Cuprotungstite leaves greenish gray to greenish yellow, Tungstite leaves yellow; luster reads vitreous, waxy, earthy on Cuprotungstite and resinous, pearly on cleavages on Tungstite.
How to tell apart: Streak differs, so Cuprotungstite leaves greenish gray to greenish yellow, Chrysocolla leaves white when pure.
Often found alongside cuprotungstite
Minerals reported to co-occur with cuprotungstite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃(WO₄)₂(OH)₂
- Mohs hardness
- 4-5
- Density
- 7.06 g/cm³
- Streak
- Greenish gray to greenish yellow
- Luster
- Vitreous, waxy, earthy
- Transparency
- Semitransparent
- Crystal system
- Tetragonal
- Crystal habit
- Crystalline, massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral typically replacing scheelite
Where rockhounds find cuprotungstite
Classic worldwide localities
- Gold Cliff claims, Cave Creek, Maricopa Co., Arizona, USA
- Green Monster mine, near White River, Kern Co., California, USA
- South Peacock mine, Seven Devils district, Adams Co., Idaho, USA
- La Paz, Baja California, Mexico
- Llamuco copper mine, east of Salamanca, Coquimbo, Chile
- Buckbarrow Beck, Corney Fell, Cumbria, England
Field-hunting tip
Where it forms: A rare secondary mineral typically replacing scheelite. If you start seeing scheelite, stolzite, raspite in float, you are in the right ground. Typical habit: crystalline, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cuprotungstite?+
Where is cuprotungstite found?+
Is cuprotungstite safe to handle?+
What rocks look like cuprotungstite?+
What minerals are found with cuprotungstite?+
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Find cuprotungstite on the map
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