Selenite Crystal Pyramid

Selenite is a variety of gypsum - hydrated calcium sulfate, CaSO₄·2H₂O - and one of the softest minerals cut as an object, Mohs 2, soft enough to mark with a fingernail. The material is usually satin spar, the fibrous gypsum whose parallel fibres give a moving, silky sheen.

That sheen is chatoyancy - light running along the fine fibres, a band of soft white light that travels as the light moves, like the sheen on satin or on still water. The body is translucent white to near-clear.

Two things follow from gypsum’s softness and its water content: selenite scratches very easily, and it dissolves in water. It asks the most careful, driest handling of anything in this range - the care below is not optional.

Asked often

Why is it called selenite?
From the Greek selene, the moon, for the soft moonlike sheen that runs across the polished stone. The name is old, and the likeness to moonlight is the reason for it.

Why is it so soft?
Selenite is gypsum, Mohs 2 - one of the softest minerals cut, soft enough to scratch with a fingernail. That softness is its nature, and the reason it is set down gently and kept from harder things.

Can it get wet?
No - keep it dry. Gypsum dissolves in water, so damp will cloud, pit, or break down the surface. Selenite is dusted with a dry cloth only.

How do I care for it?
Dry cloth only. Keep it from all water and damp, and from knocks and scratches - it is very soft. Set it apart from harder objects.

1. Set on a desk, shelf, or windowsill, apex up, on a soft surface.
2. Place it where light can pass through - the satin sheen runs up the faces toward the point.
3. Dust with a dry cloth only.
4. Keep it from all water and damp; it is very soft, so set it where it will not be knocked or scratched.

Selenite is the softest, most water-sensitive stone here. Set dry and kept from water, the satin sheen holds; this is a piece for a still shelf, not a damp sill or a surface that gets wiped wet.

Dry cloth only. Keep from all water, damp, and abrasion; set it apart from harder objects, which will scratch it. A piece to place and leave, not to handle often.

• Stone: Selenite · satin-spar gypsum
• Composition: CaSO₄·2H₂O · hydrated calcium sulfate
• Hardness: Mohs 2 (very soft)
• Character: Translucent white · travelling satin sheen
• Treatment: None · natural
• Form: Pyramid · four faces, cut and polished
• Origin: Morocco
• Care: Dry cloth only · keep from all water

The great selenite crystals are among the largest single crystals on Earth - the Cave of Crystals at Naica in Mexico holds gypsum beams many metres long, grown over hundreds of thousands of years in mineral-rich water. The same mineral, ground and fired, is the gypsum of plaster, and the alabaster carved since antiquity.

For its moonlike sheen selenite was named for the moon by the Greeks and read as a stone of light and calm across cultures - named here as what people believed. The sheen is fibre and light; what it quiets is the keeper’s.