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, so Cosalite leaves black, Bismuthinite leaves lead-gray.
How to tell apart: Streak differs, so Cosalite leaves black, Galena leaves lead-gray.
How to tell apart: Streak differs, so 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, 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
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
