RocksdayGypsum vs Selenite
To tell Gypsum from Selenite: Selenite is the clear, bladed form of this same mineral.
A soft, water-bearing calcium sulfate formed as seawater and lakes evaporate. Clear crystals are called selenite; sand-filled rosettes are 'desert roses'.
Photo: Didier Descouens, CC BY-SA 4.0
The clear, bladed variety of gypsum. Thin sheets peel off and bend, and a fingernail scratches it.
Photo: Parent Géry, CC BY-SA 3.0
Key differences
- Selenite is the clear, bladed form of this same mineral.
- Selenite is the transparent crystal form of gypsum; massive gypsum is dull and sugary.
Side by side
| Property | Gypsum | Selenite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 2 | 2 |
| Luster | Vitreous to pearly | Vitreous to pearly |
| Streak | White | White |
| Colors | Clear, White, Brown | Clear, White, Gray, Brown |
| Crystal system | Monoclinic | Monoclinic |
| Specific gravity | 2.31–2.33 | 2.3 |
| Formula | CaSO₄·2H₂O | CaSO₄·2H₂O |
| Found in | Naica, Mexico; White Sands, New Mexico | Great Salt Plains, Oklahoma; Naica, Mexico |
Properties that are the same for both are grayed out.
How to identify gypsum
- Scratches with a fingernail (hardness 2).
- Clear blades that bend slightly before snapping.
- Doesn't fizz in acid.
- Feels warm, not cold like glass.
Crystal system: Monoclinic
Full Gypsum guide →How to identify selenite
- Colorless blades or windows you can see through.
- A fingernail scratches it (hardness 2).
- Thin sheets bend and stay bent; they do not spring back like mica.
- Does not fizz in acid and does not taste salty.
Crystal system: Monoclinic
Full Selenite guide →More comparisons
Frequently asked questions
What is the difference between gypsum and selenite?
Gypsum is a mineral (CaSO₄·2H₂O) with a Mohs hardness of 2 and a vitreous to pearly luster, usually colorless, white or brown. Selenite is a mineral (CaSO₄·2H₂O) with a Mohs hardness of 2 and a vitreous to pearly luster, usually colorless, white, gray or brown.
How can you tell gypsum from selenite?
Selenite is the clear, bladed form of this same mineral. Selenite is the transparent crystal form of gypsum; massive gypsum is dull and sugary.
Could you tell them apart from a blurry close-up?
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