Stoiberite is an extremely rare copper vanadate mineral first discovered in the fumaroles of the Izalco Volcano. Collectors typically find it as microscopic, black tabular crystals forming thin encrustations on volcanic substrates.
Is this stoiberite?
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 stoiberite with a known reference. Stoiberite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: reddish brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black, reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular to blocky crystals, often as crusts.
Often confused with
Stoiberite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside stoiberite
Minerals reported to co-occur with stoiberite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₅V₂O₁₀
- Mohs hardness
- 3
- Density
- 5.0 g/cm³
- Colors
- Streak
- Reddish brown
- Luster
- Metallic
- Transparency
- Opaque, transparent only on thin edges
- Crystal system
- Monoclinic
- Crystal habit
- Tabular to blocky crystals, often as crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare mineral, deposited in vanadium-bearing sublimates in fumaroles on a basaltic volcanic cone
Where rockhounds find stoiberite
Classic worldwide localities
- Izalco volcano, El Salvador
Field-hunting tip
Where it forms: A very rare mineral, deposited in vanadium-bearing sublimates in fumaroles on a basaltic volcanic cone. If you start seeing shcherbinaite, ziesite, fingerite in float, you are in the right ground. Typical habit: tabular to blocky crystals, often as crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify stoiberite?+
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Find stoiberite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
