Corvusite is a rare sodium calcium potassium oxide, typically purplish blue-black to greenish black. Associated minerals include carnotite, fervanite and roscoelite. It was first described from the Jack claim, La Sal Mountains, Grand Co., Utah, USA.
Is this corvusite?
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 corvusite with a known reference. Corvusite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: purplish blue-black.
- 3Read the lusterHold the specimen under a strong light. Luster: “Lusterous”.
- 4Match the color rangeCompare against the expected color range: brown, bluish black, greenish black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, massive.
Often confused with
Corvusite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Corvusite is noticeably harder (Mohs 2.5-3 vs. ~1); streak differs, so Corvusite leaves purplish blue-black, Hewettite leaves brownish red; luster reads “lusterous” on Corvusite and silky to adamantine on Hewettite.
How to tell apart: Streak differs, so Corvusite leaves purplish blue-black, Pascoite leaves cadmium-yellow; luster reads “lusterous” on Corvusite and vitreous to subadamantine on Pascoite.
Often found alongside corvusite
Minerals reported to co-occur with corvusite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,Ca,K)₁₋ₓ(V⁵⁺,V⁴⁺,Fe²⁺)₈O₂₀·4H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.82 g/cm³
- Streak
- Purplish blue-black
- Luster
- “Lusterous”
- Transparency
- Opaque, transparent in very thin lamellae
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In roll-front uranium deposits in sandstone
Where rockhounds find corvusite
3 mapped spotsClassic worldwide localities
- Utah, from the Jack claim, La Sal Mountains, Grand Co., 16 km west of Gateway, Colorado, and in the Flat Top mine, Emery Co., USA
- Ponto No. 3 claim, Gypsum Valley, San Miguel Co., and the Hummer mine, Paradox Valley, Montrose Co., Colorado, USA
- Monument No. 2 mine, Monument Valley, and in the Lukachukai Mountains, Apache Co., and in the Monument No. 1 and Mitten No. 2 mines, Monument Valley, Navajo Co., Arizona, USA
- Colorado Plateau
- Mounana uranium mine, Franceville, Gabon
- Balasauskandyk, northwestern Kara-Tau Mountains, Kazakhstan
Field-hunting tip
Where it forms: In roll-front uranium deposits in sandstone. If you start seeing carnotite, fervanite, roscoelite in float, you are in the right ground. Typical habit: fibrous, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
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Find corvusite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
