Paracostibite is a rare cobalt antimony sulfide mineral that occurs primarily as metallic, anhedral grains within hydrothermal veins. It is frequently associated with other cobalt-nickel arsenides and sulfides, often requiring microscopic analysis or X-ray diffraction for definitive identification in the field.
Is this paracostibite?
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 paracostibite with a known reference. Paracostibite 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. Paracostibite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Paracostibite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: white, gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, anhedral grains.
Often confused with
Paracostibite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Cobaltite is the harder of the two (Mohs 5.5 vs. 3.5-4); streak differs — Paracostibite leaves black, Cobaltite leaves greyish-black.
How to tell apart: Gersdorffite is the harder of the two (Mohs 5.5 vs. 3.5-4); streak differs — Paracostibite leaves black, Gersdorffite leaves grayish-black.
How to tell apart: Ullmannite is the harder of the two (Mohs 5-5.5 vs. 3.5-4).
Often found alongside paracostibite
Minerals reported to co-occur with paracostibite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CoSbS
- Mohs hardness
- 3.5-4
- Density
- 7.3 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-200 per specimen
Where rockhounds find paracostibite
Classic worldwide localities
- Cobalt, Ontario, Canada
- Tunaberg, Sweden
- Stephansberg, Germany
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where paracostibite typically forms. If you start seeing cobaltite, skutterudite, nickeline in float, you are in the right ground. Field specimens usually show a massive, anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify paracostibite?+
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Find paracostibite on the map
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