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Colemanite
Colemanite is borates, CaB3O4(OH)3·H2O. In the hand, it rates 4.5 on the Mohs scale, and it runs colorless and white. Brilliant glassy colorless-to-white crystals lining cavities in soft borate rock, sharper and harder than its evaporite neighbors, with complex wedge-like faces. Borate evaporite deposits, Death Valley and Boron (California) made it famous; Turkey now dominates production.
The geology.
Colemanite carries the formula CaB3O4(OH)3·H2O. It belongs to the monoclinic system. Catalogues list it as borates.
It sits at 4.5 on the Mohs scale. The surface reads vitreous to adamantine. Light behaviour is transparent to translucent. Specific gravity runs 2.42. The streak is white. It breaks with perfect cleavage one direction; uneven fracture.
Brilliant glassy colorless-to-white crystals lining cavities in soft borate rock, sharper and harder than its evaporite neighbors, with complex wedge-like faces.
It reaches buyers as sharp glassy crystals in geode pockets, massive granular or crystal-lined cavities.
The origins.
Borate evaporite deposits, Death Valley and Boron (California) made it famous; Turkey now dominates production.
On value, the database notes: affordable; sharp Death Valley crystals are collector favorites.
Traditional associations.
In energy work traditions, colemanite is associated with calm clarity and easing transitions.
We keep this section because people ask. It sits below the geology on purpose, and none of it describes something the stone does.
Spotting the real thing.
Brilliant glassy colorless-to-white crystals lining cavities in soft borate rock, sharper and harder than its evaporite neighbors, with complex wedge-like faces.
Rarely faked; mislabeling among look-alike white borates (ulexite, howlite) is the only common mix-up.
| Looks like | How to tell them apart |
|---|---|
| Calcite | Calcite fizzes in vinegar and shows perfect rhombic cleavage; colemanite does neither |
| Danburite | Danburite is much harder (7) and forms topaz-like prisms |
| Ulexite | Ulexite is fibrous, silky, and fingernail-soft |
At-home tests.
Before anyone talks you into a lab report, these are the checks worth doing yourself on colemanite.
| Test | What you should see |
|---|---|
| Acid check | No fizz in cold vinegar (rules out calcite) |
| Scratch check | Knife scratches it with effort (4.5) |
| By eye | Flame test tinges green from boron (lab demonstration) |
Anything that scratches, burns or dissolves the piece is a lab job. Get it appraised rather than testing it apart.
Care & handling.
At 4.5 on the Mohs scale this is a soft material. Keep it as a display piece, store it apart from harder stones, and skip daily-wear settings.
It breaks with perfect cleavage one direction; uneven fracture, which is worth knowing before you set it or drop it.
Warm water and a soft cloth clean almost everything. Ultrasonic tanks, steamers and household cleaners are where pieces get ruined.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is CaB3O4(OH)3·H2O. Crystal system: Monoclinic. Specific gravity: 2.42. Streak: White. Cleavage and fracture: Perfect cleavage one direction; uneven fracture.
How it reaches the market
Borate evaporite deposits, Death Valley and Boron (California) made it famous; Turkey now dominates production.
What it gets confused with
Calcite: Calcite fizzes in vinegar and shows perfect rhombic cleavage; colemanite does neither. Danburite: Danburite is much harder (7) and forms topaz-like prisms. Ulexite: Ulexite is fibrous, silky, and fingernail-soft.
What it is worth
Affordable; sharp Death Valley crystals are collector favorites.
Where buyers get caught
Rarely faked; mislabeling among look-alike white borates (ulexite, howlite) is the only common mix-up.
One more thing
Named for William Coleman, whose Harmony Borax Works hauled the ore out of Death Valley behind the legendary twenty-mule teams in the 1880s.
An education-first guide.
No product links here. We do not sell colemanite, and a guide that only covers our own shelves would not be much of a guide.
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