Krupkaite is a rare lead-copper-bismuth sulfide that typically forms as lead-gray, acicular or fibrous needle-like crystals. It is most commonly identified in hydrothermal tin-tungsten deposits, often occurring in intimate intergrowths with other bismuth sulfosalts. Because of its microscopic nature and similarity to other bismuth minerals, precise identification usually requires X-ray diffraction or electron microprobe analysis.
Is this krupkaite?
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 krupkaite with a known reference. Krupkaite 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. Krupkaite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Krupkaite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: lead-gray, steel-gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular to fibrous aggregates.
Often confused with
Krupkaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Krupkaite is noticeably harder (Mohs 3.5 vs. 2); streak differs — Krupkaite leaves black, Bismuthinite leaves lead-gray.
How to tell apart: Krupkaite is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs — Krupkaite leaves black, Aikinite leaves lead-gray.
Often found alongside krupkaite
Minerals reported to co-occur with krupkaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbCuBi₃S₆
- Mohs hardness
- 3.5
- Density
- 7.35 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular to Fibrous Aggregates
- Cleavage
- Good On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Tin-tungsten Veins
- Typical price
- $50-300 per specimen depending on size and association
Where rockhounds find krupkaite
Classic worldwide localities
- Krupka, Czech Republic
- Teluit, Russia
- Gladhammar, Sweden
- Moina, Tasmania
- Binn Valley, Switzerland
Field-hunting tip
Look in hydrothermal tin-tungsten veins country — that is the host setting where krupkaite typically forms. If you start seeing bismuthinite, galena, chalcopyrite in float, you are in the right ground. Field specimens usually show a acicular to fibrous aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find krupkaite on the map
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