Černýite is a rare copper cadmium tin sulfide found primarily in granitic pegmatites. It typically appears as an opaque, steel-gray massive mineral and is nearly impossible to distinguish from other stannite-group minerals without chemical analysis like EDS or XRD.
Is this černýite?
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 černýite with a known reference. Černýite sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: steel gray, gray.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: massive, granular, inclusions.
Often confused with
Černýite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Černýite leaves black, Stannite leaves blackish.
How to tell apart: Streak differs, so Černýite leaves black, Sphalerite leaves pale brown to pale yellow and white; luster reads metallic on Černýite and resinous to adamantine on Sphalerite.
Often found alongside černýite
Minerals reported to co-occur with černýite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂CdSnS₄
- Mohs hardness
- ~4
- Density
- 4.776 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Massive, granular, inclusions
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- A rare constituent of complex zoned pegmatites, as a component of a very minor sulfide mineral suite
Where rockhounds find černýite
Classic worldwide localities
- Hugo (type locality) and Peerless mines, near Keystone, Pennington Co., South Dakota, USA
- Tanco pegmatite at Bernic Lake, southeastern Manitoba, Canada (type locality)
- Barquilla deposit, Salamanca Province, Spain
Field-hunting tip
Where it forms: A rare constituent of complex zoned pegmatites, as a component of a very minor sulfide mineral suite. If you start seeing pyrrhotite, sphalerite, hawleyite in float, you are in the right ground. Typical habit: massive, granular, inclusions. Train your eye for that shape before scanning the outcrop.
Common questions
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Find černýite on the map
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