Niccolite Identification Guide
How to identify niccolite (nickeline), a pale copper-red nickel arsenide, by its metallic luster, high density, streak, and tarnish.
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What Niccolite Looks Like
Niccolite (also called nickeline, NiAs) is a nickel arsenide with a distinctive pale copper-red to flesh-pink metallic color that tarnishes to grey or blackish on exposure. It is a heavy, opaque metallic mineral.
- Color: pale copper-red / flesh-pink when fresh, dulling to grey-black tarnish
- Luster: metallic
- Transparency: opaque
- Habit: usually massive, granular, or reniform (botryoidal) crusts; well-formed crystals are rare
- Associations: often with other nickel-cobalt-arsenic ores (smaltite, cobaltite, silver)
Step-by-Step Field ID Checklist
- Note the unusual pale copper-red/pinkish metallic color — not the orange-red of native copper.
- Check for grey/blackish tarnish on weathered surfaces.
- Heft it — niccolite is very heavy (high density).
- Test the streak on unglazed porcelain: pale brownish-black.
- Confirm metallic luster and opacity; test hardness (about 5-5.5, scratches with a knife only with effort).
Key Diagnostic Tests
- Mohs hardness: 5-5.5.
- Streak: pale brownish-black.
- Cleavage/fracture: no good cleavage; uneven to conchoidal fracture, brittle.
- Density: very high, SG ~7.8 — a key diagnostic (feels notably heavy).
- Magnetism: generally non-magnetic to weakly responsive.
- Caution: niccolite is an arsenide; heating or acid testing can release toxic arsenic fumes — avoid, and wash hands after handling.
Common Look-Alikes and How to Tell Them Apart
- Native copper: copper is a brighter rose-red, softer (2.5-3), malleable (dents rather than chips), and gives a metallic copper-red streak; niccolite is harder, brittle, and paler.
- Pyrrhotite: bronze-brown and usually magnetic; niccolite is paler copper-pink and not strongly magnetic.
- Bornite ("peacock ore"): tarnishes iridescent purple-blue; niccolite tarnishes plain grey-black.
- Breithauptite (NiSb): very similar but a more violet/lilac copper-red; lab analysis distinguishes the antimonide from the arsenide.
- Copper-bearing sulfides (chalcopyrite): brass-yellow, softer, with a greenish-black streak.
Where It Is Found
Niccolite occurs in hydrothermal vein deposits with nickel-cobalt-silver-arsenic ores, notably at Cobalt (Ontario, Canada), the Erzgebirge and Mansfeld (Germany), Jáchymov (Czech Republic), and Sudbury-type nickel districts.
Frequently asked questions
How can you tell if it's real niccolite?
Niccolite shows a pale copper-red metallic color that tarnishes grey-black, a hardness of 5-5.5, a pale brownish-black streak, brittleness, and a very high density around 7.8. Handle carefully because it is a nickel arsenide.
What is the difference between niccolite and native copper?
Native copper is a brighter rose-red, soft (2.5-3) and malleable so it dents rather than chips, and gives a copper-red streak. Niccolite is paler, harder, brittle, and gives a brownish-black streak.
Is niccolite the same as nickeline?
Yes. Nickeline is the modern accepted mineral name for the nickel arsenide NiAs; niccolite is the older traditional name for the same mineral.
Is niccolite dangerous to handle?
Niccolite is a nickel arsenide, so heating it or testing it with acid can release toxic arsenic fumes. Handle it minimally, avoid dust and heat, and wash your hands afterward.
Niccolite identified by the community
Recent Niccolite specimens identified with Rock Identifier.
