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Plancheite
Plancheite is inosilicate (copper), Cu₈Si₈O₂₂(OH)₄·H₂O. In the hand, it rates 5.5 on the Mohs scale, and it runs sky blue and turquoise blue. Sky-blue silky fiber-balls and crusts from copper country, like shattuckite's lighter-blue cousin with a satin spar sheen. Oxidized copper deposits: DR Congo (Katanga, the classics), Namibia, Arizona (USA).
The geology.
Plancheite carries the formula Cu₈Si₈O₂₂(OH)₄·H₂O. It belongs to the orthorhombic system. The trade files it under inosilicate (copper).
It sits at 5.5 on the Mohs scale. The surface reads silky. Light behaviour is translucent to opaque. Specific gravity runs 3.65 to 3.8. The streak is pale blue. It breaks with fibrous; uneven fracture.
Sky-blue silky fiber-balls and crusts from copper country, like shattuckite's lighter-blue cousin with a satin spar sheen.
Common cuts are silky botryoidal crusts, radiating fiber balls or massive seams.
The origins.
Oxidized copper deposits: DR Congo (Katanga, the classics), Namibia, Arizona (USA).
On value, the database notes: collector mineral; silky Congo botryoids are mid-range.
Traditional associations.
In energy work traditions, associated with calm articulate expression, often borrowed from its shattuckite kin.
Included for completeness. Tradition is worth knowing about, and it is worth keeping separate from the mineralogy.
Spotting the real thing.
Sky-blue silky fiber-balls and crusts from copper country, like shattuckite's lighter-blue cousin with a satin spar sheen.
| Looks like | How to tell them apart |
|---|---|
| Shattuckite | Shattuckite runs deeper royal blue; plancheite paler sky-blue, the pair intergrow and labs split fine calls |
| Chrysocolla | Chrysocolla is softer, waxier, never silky-fibrous |
| Blue satin spar (celestite/gypsum) | Gypsum scratches with a fingernail; plancheite resists a knife better and is heavier |
At-home tests.
These checks cost nothing. Daylight, a 10x loupe and a little patience are the whole kit for plancheite.
| Test | What you should see |
|---|---|
| By eye | Silky radiating fiber structure |
| Scratch check | Harder than chrysocolla (knife resists) |
| By eye | Noticeably heavy for sky blue |
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 fibrous; 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.
Copper mineral, wash hands after handling raw material.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is Cu₈Si₈O₂₂(OH)₄·H₂O. Crystal system: Orthorhombic. Specific gravity: 3.65 to 3.8. Streak: Pale blue. Cleavage and fracture: Fibrous; uneven fracture.
How it reaches the market
Oxidized copper deposits: DR Congo (Katanga, the classics), Namibia, Arizona (USA).
What it gets confused with
Shattuckite: Shattuckite runs deeper royal blue; plancheite paler sky-blue, the pair intergrow and labs split fine calls. Chrysocolla: Chrysocolla is softer, waxier, never silky-fibrous. Blue satin spar (celestite/gypsum): Gypsum scratches with a fingernail; plancheite resists a knife better and is heavier.
What it is worth
Collector mineral; silky Congo botryoids are mid-range.
One more thing
Plancheite and shattuckite confused mineralogists for decades, two silky blue copper silicates that insist on growing together.
An education-first guide.
There is nothing to buy on this page. Plancheite 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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