Vanarsite is a rare sodium calcium arsenic oxide, typically very dark blue. It is a secondary mineral formed by the oxidation of montroseite-corvusite assemblages in a moist environment. It was first described from Packrat mine, Gateway district, Mesa County, Colorado, USA.
Is this vanarsite?
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 vanarsite with a known reference. Vanarsite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Vanarsite leaves a grayish blue streak.
- 3Read the lusterHold the specimen under a strong light. Vanarsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crusts, aggregates of lath-like crystals.
Often confused with
Vanarsite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Vanarsite leaves grayish blue, Pascoite leaves yellow.
How to tell apart: Vanarsite is noticeably harder (Mohs 2 vs. approx 1); streak differs, so Vanarsite leaves grayish blue, Hewettite leaves brownish red; luster reads vitreous on Vanarsite and silky to adamantine on Hewettite.
Often found alongside vanarsite
Minerals reported to co-occur with vanarsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₁₂(As³⁺V⁵⁺₈.₅V⁴⁺₃.₅As⁵⁺₆O₅₁)₂·78H₂O
- Mohs hardness
- 2
- Density
- 2.48 g/cm³
- Colors
- Streak
- Grayish Blue
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Crusts, Aggregates of Lath-like Crystals
- Cleavage
- Fair On {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sandstone
Where rockhounds find vanarsite
Classic worldwide localities
- Vanadium Queen Mine, Utah, USA
Field-hunting tip
Look in sandstone country, the host setting where vanarsite typically forms. If you start seeing gypsum, barite, montroseite in float, you are in the right ground. Field specimens usually show a crusts, aggregates of lath-like crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify vanarsite?+
Where is vanarsite found?+
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Find vanarsite on the map
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