Pascoite is a rare secondary vanadium mineral that typically forms as bright orange, tabular crystals or efflorescent crusts in arid uranium-vanadium mining districts. It is highly soluble in water and often found as a post-mining alteration product on sandstone walls, requiring protection from high humidity to prevent dehydration.
Is this pascoite?
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 pascoite with a known reference. Pascoite sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: cadmium-yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to subadamantine.
- 4Match the color rangeCompare against the expected color range: yellow brown, yellow orange, red orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: encrustations, granular.
Often confused with
Pascoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Pascoite leaves cadmium-yellow, Carnotite leaves strontian-yellow; luster reads vitreous to subadamantine on Pascoite and dull, earthy; silky when crystalline on Carnotite.
How to tell apart: Streak differs, so Pascoite leaves cadmium-yellow, Tyuyamunite leaves light yellow; luster reads vitreous to subadamantine on Pascoite and adamantine, pearly on {001}, may be dull to waxy if massive on Tyuyamunite.
How to tell apart: Pascoite is noticeably harder (Mohs ~2.5 vs. ~1); streak differs, so Pascoite leaves cadmium-yellow, Hewettite leaves brownish red; luster reads vitreous to subadamantine on Pascoite and silky to adamantine on Hewettite.
Often found alongside pascoite
Minerals reported to co-occur with pascoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃V₁₀O₂₈·17H₂O
- Mohs hardness
- ~2.5
- Density
- 2.455 g/cm³
- Streak
- Cadmium-yellow
- Luster
- Vitreous to subadamantine
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Encrustations, granular
- Cleavage
- {010}, distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Leached from near-surface V-oxides by ground water; as efflorescences in mines
Where rockhounds find pascoite
Classic worldwide localities
- Hawkeye, Burro, and Deremo-Snyder mines, near Slick Rock, San Miguel Co., Colorado, USA
- Bitter Creek, Mill No. 1, and Peanut mines, Uravan district, Montrose Co., Colorado, USA
- Corvusite and La Sal No. 2 mines, Gateway district, Mesa Co., Colorado, USA
- Rifle mine, Garfield Co., Colorado, USA
- Minasragra, 46 km from Cerro de Pasco, Peru
- Urcal deposit, La Rioja Province, Argentina
Field-hunting tip
Where it forms: Leached from near-surface V-oxides by ground water; as efflorescences in mines. If you start seeing carnotite in float, you are in the right ground. Typical habit: encrustations, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pascoite?+
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Find pascoite on the map
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