sulfates
Satin spar
Ca(SO4)·2H2O
- Crystal system
- monoclinic
- Hardness
- 2 on the Mohs scale
- Lustre
- silky
- Colour
- White, with a moving silky sheen along the fibres
- Where it forms
- In veins, where gypsum crystallised as parallel fibres across a fracture rather than as blocky crystals.
- Chiefly from
- MoroccoEnglandMexico
Why it is that colour
The sheen is chatoyancy from a parallel fibrous structure, the same optical effect as in a cat’s eye stone, and it is why the material is so recognisable.
Safety
Safe to handle, soft and water-soluble. It will dissolve if left wet.
Where it comes from
Overwhelmingly Moroccan. This is the material of essentially every selenite wand, tower, lamp and charging plate on the market, sold under a name that belongs to a different variety of the same mineral.
Historical use
Used as a minor ornamental stone. In England it was worked in Nottinghamshire and Derbyshire, where it was sometimes called Derbyshire spar — a name also confusingly applied to fluorite.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
No traditional attribution of its own. Everything attributed to it is attributed under the name selenite.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Sold as this, but not
Worth knowing
This is the most widespread naming substitution in the whole crystal trade, and it is almost entirely harmless, which makes it a useful example.
Selenite proper is the transparent, blocky, glassy form of gypsum. Satin spar is the white, fibrous, silky form. They are the same mineral, so nothing is being faked in any chemical sense — but the wands, towers, lamps and "charging plates" sold as selenite are, essentially without exception, satin spar. The trade adopted the more evocative name and stopped distinguishing.
Worth noting because it shows how naming drifts in a market where nobody has any reason to correct it. No one is defrauded; the buyer gets gypsum either way. The name simply stopped meaning what it means.
Identity checked against IMA-CNMNC master list, June 2025.