Cuprobismutite is a rare copper-silver-bismuth sulfosalt typically found in hydrothermal polymetallic vein systems. Collectors usually identify it by its dark, metallic appearance and common association with other complex bismuth-bearing sulfides.
Is this cuprobismutite?
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 cuprobismutite with a known reference. Cuprobismutite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cuprobismutite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Cuprobismutite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: dark gray, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, anhedral grains, striated crystals.
Often confused with
Cuprobismutite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Cuprobismutite is noticeably harder (Mohs 3.5 vs. 2.5).
How to tell apart: Cuprobismutite is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs — Cuprobismutite leaves black, Aikinite leaves lead-gray.
How to tell apart: Cuprobismutite is noticeably harder (Mohs 3.5 vs. 2); streak differs — Cuprobismutite leaves black, Emplectite leaves lead-gray.
Often found alongside cuprobismutite
Minerals reported to co-occur with cuprobismutite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₈AgBi₉S₁₈
- Mohs hardness
- 3.5
- Density
- 6.7 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Massive, Anhedral Grains, Striated Crystals
- Cleavage
- None Observed
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Hydrothermal Veins
- Typical price
- $50-500 thumbnail depending on size and provenance
Where rockhounds find cuprobismutite
Classic worldwide localities
- Moctezuma, Mexico
- Berezovsk, Russia
- Colorado, USA
- Bolivia
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where cuprobismutite typically forms. If you start seeing quartz, chalcopyrite, pyrite in float, you are in the right ground. Field specimens usually show a massive, anhedral grains, striated crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cuprobismutite?+
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Find cuprobismutite on the map
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