Weissbergite is an extremely rare thallium-antimony sulfide mineral typically found as delicate acicular crystals. It is primarily known from the historic Allchar mine in North Macedonia, where it occurs within epithermal sulfosalt deposits. Collectors should treat it with high care due to the toxic nature of thallium.
Is this weissbergite?
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 weissbergite with a known reference. Weissbergite sits at Mohs 1.5, 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: bright metallic.
- 4Match the color rangeCompare against the expected color range: steel gray.
- 5Look at form & habitCrystal system: triclinic. Typical habit: irregular grains, striated.
Often confused with
Weissbergite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Weissbergite leaves dark gray, Stibnite leaves lead-gray; luster reads bright metallic on Weissbergite and metallic, splendent on cleavage surfaces on Stibnite.
How to tell apart: Streak differs, so Weissbergite leaves dark gray, Orpiment leaves pale lemon-yellow; luster reads bright metallic on Weissbergite and resinous, pearly on cleavage surface on Orpiment.
Often found alongside weissbergite
Minerals reported to co-occur with weissbergite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- TlSbS₂
- Mohs hardness
- 1.5
- Density
- 5.79 g/cm³
- Colors
- Streak
- Dark gray
- Luster
- Bright metallic
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Irregular grains, striated
- Cleavage
- One perfect, two excellent, one good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In late-stage hydrothermal veins that brecciate silicified dolomitic carbonate rocks
Where rockhounds find weissbergite
Classic worldwide localities
- East ore zone, Carlin mine, 50 km northwest of Elko, Lynn district, Eureka Co., Nevada, USA
- Lookout Pass, Toole Co., Utah, USA
- Alšar (Allchar), near Rošden, Macedonia
Field-hunting tip
Where it forms: In late-stage hydrothermal veins that brecciate silicified dolomitic carbonate rocks. If you start seeing stibnite, quartz in float, you are in the right ground. Typical habit: irregular grains, striated. Train your eye for that shape before scanning the outcrop.
Common questions
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Find weissbergite on the map
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