Alloclasite
A variety of Minerals
What is Alloclasite?
Alloclasite ((Co,Fe)AsS) is a sulfosalt mineral. It is a member of the arsenopyrite group. Alloclasite crystallizes in the monoclinic system and typically forms as columnar to radiating acicular prismatic clusters. It is an opaque steel-gray to silver-white, with a metallic luster and a black streak. It is brittle with perfect cleavage, a Mohs hardness of 5 and a specific gravity of 5.91–5.95. It was first described in 1866 for an occurrence in Romania. Its name is derived from Greek for "other" and "to break," in reference to its distinct cleavage which distinguished it from the similar appearing mineral marcasite. The mineral is monoclinic in the P21 space group.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Alloclasite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Alloclasite Localities Map
See where Alloclasite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Quick Facts
Physical Properties
- Color
- Steel gray to silver
- Hardness (Mohs)
- 5
- Density
- 6.188 g/cm³
- Streak
- Nearly black
Chemical Properties
- Chemical Formula
- Co1-xFexAsS (x ≈ 0-0.35)
- Elements
- As, Co, Fe, S
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Alloclasite FAQs
How do I identify Alloclasite?
Alloclasite can be identified by its hardness of 5 on the Mohs scale, Steel gray to silver color. Look for these key characteristics when examining specimens.
What color is Alloclasite?
Alloclasite typically appears in Steel gray to silver. Color can vary depending on impurities and formation conditions.
How hard is Alloclasite?
Alloclasite has a hardness of 5 on the Mohs scale. This gives it moderate hardness.
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