The Mohs 2 reference — a fingernail scratches it. Soft, light, water-soluble, and mislabelled constantly.
Morocco, Mexico (Naica), Oklahoma, Australia5 field tests
Selenite is a variety of gypsum, calcium sulphate, and it is the softest material anyone is likely to buy as a decorative stone: hardness 2, which means a fingernail marks it. That single fact governs everything about owning it. It scratches if you look at it wrongly, it should never be washed, and it will dissolve in water given time.
It is also the mineral most often sold under the wrong name, though usually harmlessly. The fibrous, silky, translucent white material in tower lamps and charging plates is properly satin spar rather than selenite proper, which is the transparent bladed form. The trade uses selenite for both, and has for long enough that arguing is futile.
There is no meaningful counterfeiting problem here, because selenite is abundant and cheap. What there is instead is a great deal of confusion with harder white minerals — calcite, quartz, howlite, aragonite — and one properly useful test that separates it from all of them in a second.
Selenite's identification is a single test: scratch it with a fingernail. At hardness 2 it marks readily, which no other common white mineral does — calcite at 3 needs a coin, quartz at 7 needs a file, and howlite at 3.5 resists a nail.
The practical consequences are worth as much as the identification. Water dissolves gypsum, so a selenite lamp wiped with a damp cloth develops a dull etched patch, and a piece left in a bathroom slowly degrades. Dust it dry.
| Property | Selenite | What it separates it from |
|---|---|---|
| Mohs hardness | 2 — a fingernail scratches it | Calcite (3), howlite (3.5), quartz (7) |
| Solubility in water | Slowly soluble | Every silicate; calcite is far less soluble |
| Specific gravity | 2.3 | Noticeably light — calcite is 2.71 |
| Cleavage | Perfect in one direction, plus two poorer | Splits into thin flexible sheets |
| Reaction to vinegar | None | Calcite, which effervesces |
| Habit | Bladed, fibrous satin spar, desert rose, fishtail twins | — |
| Lustre | Pearly to silky, sometimes vitreous | — |
| Streak | White | — |
The nail test and the vinegar test together are conclusive: soft enough to scratch with a nail, and no fizz, means gypsum rather than calcite.
Ordered by how much each one proves. The decisive tests are worth your first two minutes; the supporting ones only matter once those agree.
A fingernail is about 2.5 on the Mohs scale and selenite is 2, so it marks without effort — leaving a visible white line on a translucent surface. This is decisive against every other common white mineral, and it is the reason selenite must be handled carefully rather than tested casually. Do it on the base.
Selenite is a sulphate, not a carbonate, so it does not effervesce. This separates it from calcite and aragonite, which are the white minerals it is most often confused with and which fizz briskly. A soft white mineral that does not fizz is gypsum.
Gypsum cleaves perfectly in one direction and the resulting sheets are thin, slightly flexible and can be peeled apart with a fingernail — the mineral was used as window glazing for exactly this reason. Calcite cleaves into rigid rhombs instead, and quartz does not cleave at all.
At 2.3 specific gravity selenite is genuinely light, below quartz and well below calcite. A large tower that feels insubstantial for its size is behaving correctly.
Four forms cover almost everything sold: transparent bladed selenite, silky fibrous satin spar, the sand-cemented rosettes called desert rose, and the V-shaped fishtail twins. Desert rose in particular is often assumed to be a separate mineral and is simply gypsum with sand incorporated as it grew.
Each of these is checked differently. The ones with their own page have enough that is specific to them to be worth reading separately.
Gypsum rosettes grown in sand, so the sand is part of the crystal.
Read within the checks aboveSpecimen figures rather than gem figures, for material in honest condition. Most finds are worth very little, and saying so plainly is more useful than encouraging you.
| Form | What it typically fetches | Note |
|---|---|---|
| Satin spar tower or plate | $5 – 30 | Sold by size; abundant from Morocco |
| Desert rose | $3 – 25 | Rosette form and completeness |
| Transparent bladed selenite | $10 – 60 | Clarity and undamaged blades |
| Fishtail twin specimen | $20 – 150 | Twinning and condition |
Selenite is one of the cheapest decorative minerals there is, and its softness means condition dominates value — an undamaged piece is worth several times a scratched one.
Lovenhall StoneThe tests tell you what it is. The instrument reads a photograph and offers a name to start from — then hands you back to the tile and the coin, which are what settle it.