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, so Cuprobismutite leaves black, Aikinite leaves lead-gray.
How to tell apart: Cuprobismutite is noticeably harder (Mohs 3.5 vs. 2); streak differs, so 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, 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
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Find cuprobismutite on the map
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