Weibullite is a rare lead-bismuth sulfosalt that typically occurs as lead-gray acicular to fibrous crystalline masses within hydrothermal veins. It is most easily identified by its distinctive metallic luster and association with other bismuth-bearing sulfide minerals, often requiring X-ray diffraction for definitive field identification.
Is this weibullite?
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 weibullite with a known reference. Weibullite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: steel gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, prismatic.
Often confused with
Weibullite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Weibullite leaves dark gray, Galenobismutite leaves black.
How to tell apart: Streak differs, so Weibullite leaves dark gray, Cosalite leaves black.
How to tell apart: Streak differs, so Weibullite leaves dark gray, Aikinite leaves grayish black.
Often found alongside weibullite
Minerals reported to co-occur with weibullite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₀.₃Pb₅.₃Bi₈.₃(S,Se)₁₈
- Mohs hardness
- 2-2.5
- Density
- 6.97-7.145 g/cm³
- Colors
- Streak
- Dark gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, prismatic
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Intimately intergrown with laitakarite and bismuthinite in a “hornblende” rock
Where rockhounds find weibullite
Classic worldwide localities
- Falun, Kopparberg, Sweden
Field-hunting tip
Where it forms: Intimately intergrown with laitakarite and bismuthinite in a “hornblende” rock. If you start seeing laitakarite, bismuthinite, gold in float, you are in the right ground. Typical habit: massive, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify weibullite?+
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What rocks look like weibullite?+
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Find weibullite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
