Guanajuatite is a rare bismuth selenide mineral typically found as metallic, lead-gray acicular or fibrous aggregates within hydrothermal veins. It is most famously associated with the mining district of Guanajuato, Mexico, where it was first discovered. Collectors prize it for its unique chemistry and metallic luster, though it is often brittle and requires careful handling.
Is this guanajuatite?
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 guanajuatite with a known reference. Guanajuatite 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. Guanajuatite leaves a lead-gray streak.
- 3Read the lusterHold the specimen under a strong light. Guanajuatite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: lead-gray, bluish-gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, fibrous, granular, massive.
Often confused with
Guanajuatite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside guanajuatite
Minerals reported to co-occur with guanajuatite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₂Se₃
- Mohs hardness
- 2.5
- Density
- 7.15 g/cm³
- Colors
- Streak
- Lead-gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, Fibrous, Granular, Massive
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $20-150 for thumbnail to small cabinet specimens
Where rockhounds find guanajuatite
Classic worldwide localities
- Guanajuato, Mexico
- Tasna, Bolivia
- Sierra de Cacheuta, Argentina
- Tarkwa, Ghana
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where guanajuatite typically forms. If you start seeing clausthalite, bismuth, selenite in float, you are in the right ground. Field specimens usually show a acicular, fibrous, granular, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify guanajuatite?+
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Is guanajuatite safe to handle?+
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Find guanajuatite on the map
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