Cosalite is a lead-bismuth sulfide that typically forms distinct, elongated, needle-like or fibrous masses. Collectors often look for it within hydrothermal vein deposits where it manifests as radiating clusters or felted mats associated with other sulfide minerals.
Is this cosalite?
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 cosalite with a known reference. Cosalite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cosalite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Cosalite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: lead-gray, steel-gray, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous, needle-like, massive, capillary.
Often confused with
Cosalite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Cosalite leaves black, Bismuthinite leaves lead-gray.
How to tell apart: Streak differs — Cosalite leaves black, Galena leaves lead-gray.
How to tell apart: Streak differs — Cosalite leaves black, Jamesonite leaves gray-black.
Often found alongside cosalite
Minerals reported to co-occur with cosalite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂Bi₂S₅
- Mohs hardness
- 2.5-3
- Density
- 6.8-7.2 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous, Needle-like, Massive, Capillary
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Ore of Bismuth
- Host rock
- Hydrothermal Sulfide Veins
- Typical price
- $10-150 per specimen depending on size and crystal quality
Where rockhounds find cosalite
Classic worldwide localities
- Cosala, Mexico
- Silver Bell Mine, Arizona, USA
- Nordmark, Sweden
- Carrock Mine, UK
- Baita Bihor, Romania
Field-hunting tip
Look in hydrothermal sulfide veins country — that is the host setting where cosalite typically forms. If you start seeing galena, pyrite, chalcopyrite in float, you are in the right ground. Field specimens usually show a fibrous, needle-like, massive, capillary habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cosalite on the map
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