Kochkarite is a rare lead bismuth telluride mineral found primarily in gold-bearing hydrothermal deposits. It is often identified by its metallic luster and soft, platy or tabular crystal habits, requiring X-ray diffraction or microprobe analysis for positive identification.
Is this kochkarite?
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 kochkarite with a known reference. Kochkarite sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: lead gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: silver gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: tabular crystals, massive.
Often confused with
Kochkarite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Kochkarite is noticeably harder (Mohs 3.5-4 vs. 1.5-2); streak differs, so Kochkarite leaves lead gray, Tetradymite leaves pale steel-gray.
How to tell apart: Kochkarite is noticeably harder (Mohs 3.5-4 vs. 1.5-2); streak differs, so Kochkarite leaves lead gray, Tellurobismuthite leaves pale lead-gray.
Often found alongside kochkarite
Minerals reported to co-occur with kochkarite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbBi₄Te₇
- Mohs hardness
- 3.5-4
- Density
- 13.0 g/cm³
- Colors
- Streak
- Lead gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Tabular crystals, massive
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the heavy mineral fraction of concentrates (Krokhalin deposit, Russia)
Where rockhounds find kochkarite
Classic worldwide localities
- Gould-Curry mine, Comstock Lode, Virginia City, Storey Co., Nevada, USA
- Krokhalin Au–Sb deposit, 60 km southeast of Yagodnoye, basin of the Kolyma River, Magadan region, Sakha, Russia (type locality)
- A prospect near Marcelita, about 70 km southeast of Copiapó, Atacama, Chile
Field-hunting tip
Where it forms: In the heavy mineral fraction of concentrates (Krokhalin deposit, Russia). If you start seeing copper, stibnite, berthierite in float, you are in the right ground. Typical habit: tabular crystals, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kochkarite?+
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What rocks look like kochkarite?+
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Find kochkarite on the map
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