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Cobaltite
Cobaltite is sulfide (sulfarsenide), CoAsS. In the hand, it rates 5.5 on the Mohs scale, and it runs silver white with rosy tint and steel gray. Silver-white metallic crystals with a faint rosy blush, in striated cube-like forms, pyrite's shape wearing silver-pink instead of brass.
The geology.
Cobaltite carries the formula CoAsS. It belongs to the orthorhombic (pseudo-cubic) system. The trade files it under sulfide (sulfarsenide).
It sits at 5.5 on the Mohs scale. The surface reads metallic. Light behaviour is opaque. Specific gravity runs 6.0 to 6.3. The streak is gray-black. It breaks with perfect cubic-like cleavage; uneven fracture.
Silver-white metallic crystals with a faint rosy blush, in striated cube-like forms, pyrite's shape wearing silver-pink instead of brass.
Common cuts are pseudo-cubic and pyritohedral crystals or granular ore.
The origins.
Skarns and veins: Tunaberg (Sweden, classic sharp crystals), Cobalt (Ontario, Canada), Morocco (Bou Azzer).
On value, the database notes: collector mineral; sharp Swedish crystals are prized.
Traditional associations.
In energy work traditions, cobaltite has little established lore; it is collected for its sharp silvery crystals.
Included for completeness. Tradition is worth knowing about, and it is worth keeping separate from the mineralogy.
Spotting the real thing.
Silver-white metallic crystals with a faint rosy blush, in striated cube-like forms, pyrite's shape wearing silver-pink instead of brass.
| Looks like | How to tell them apart |
|---|---|
| Pyrite | Pyrite is brass yellow; cobaltite is silvery with a pink cast |
| Arsenopyrite | Very similar, arsenopyrite forms wedges rather than cubes; lab confirmation is common |
| Skutterudite | Its arsenide cousin is tin-white without the rosy tint, locality often decides |
At-home tests.
These checks cost nothing. Daylight, a 10x loupe and a little patience are the whole kit for cobaltite.
| Test | What you should see |
|---|---|
| By eye | Rosy-silver tint |
| By eye | Pseudo-cubic striated crystals |
| By eye | Heavy (SG ~6.1) |
If these checks leave you unsure, that is what appraisers are for. Do not file, heat or soak a piece to find out.
Care & handling.
At 5.5 on the Mohs scale it handles careful wear but scratches against quartz and dust. Store it separately and take rings off before rough work.
It breaks with perfect cubic-like cleavage; uneven fracture, which is worth knowing before you set it or drop it.
Most damage happens during cleaning, not wearing. Avoid steamers, ultrasonic tanks and anything from under the sink.
Contains arsenic, stable as a specimen, but wash hands after handling and never grind or heat it.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is CoAsS. Crystal system: Orthorhombic (pseudo-cubic). Specific gravity: 6.0 to 6.3. Streak: Gray-black. Cleavage and fracture: Perfect cubic-like cleavage; uneven fracture.
How it reaches the market
Skarns and veins: Tunaberg (Sweden, classic sharp crystals), Cobalt (Ontario, Canada), Morocco (Bou Azzer).
What it gets confused with
Pyrite: Pyrite is brass yellow; cobaltite is silvery with a pink cast. Arsenopyrite: Very similar, arsenopyrite forms wedges rather than cubes; lab confirmation is common. Skutterudite: Its arsenide cousin is tin-white without the rosy tint, locality often decides.
What it is worth
Collector mineral; sharp Swedish crystals are prized.
One more thing
Weathered cobaltite blooms pink erythrite on its surface, the mineral literally blushes as it decays.
An education-first guide.
There is nothing to buy on this page. Cobaltite is not part of our catalogue, and the guide is here anyway because somebody searching the name deserves a straight answer.
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