Comparison · Minerals
Gypsum vs Selenite
Gypsum and Selenite are easy to confuse because both are minerals. Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Gypsum and Selenite
- Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Gypsum is Transparent to translucent, Selenite is transparent.
- They overlap in clear, gray, and pink, but Gypsum also comes in yellow and brown.
- Well-formed crystals give it away: Gypsum is Monoclinic, Selenite is monoclinic.
Gypsum vs Selenite properties
| Property | Gypsum | Selenite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 2 | 2 |
| Luster | Vitreous, pearly, or silky (fibrous), earthy when massive | vitreous |
| Streak | White | White |
| Transparency | Transparent to translucent | transparent |
| Specific gravity | 2.3–2.35 | 2.3 |
| Crystal system | Monoclinic | monoclinic |
| Common colors | Colorless, White, Gray, Yellow, Brown, Pink | Colorless, White, Peach, Gray |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $5–$150+ |
Which is more valuable?
Typical specimens of Gypsum and Selenite trade in a similar range, around $20.
About Gypsum
Gypsum is a soft, common evaporite mineral, calcium sulfate dihydrate with the formula CaSO4·2H2O, that defines hardness 2 on the Mohs scale and can be scratched with a fingernail. It precipitates from evaporating saline water and occurs in forms ranging from transparent selenite crystals to fibrous satin spar and massive alabaster. Gypsum is also the principal raw material used to manufacture plaster of Paris and drywall.
About Selenite
Selenite is a crystalline form of gypsum known for its transparency and moon-like glow. The Cave of Crystals in Mexico contains selenite crystals up to 12 meters long.
Gypsum vs Selenite FAQ
Is Gypsum the same as Selenite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Gypsum from Selenite?
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Gypsum is Transparent to translucent, Selenite is transparent. They overlap in clear, gray, and pink, but Gypsum also comes in yellow and brown.
Which is harder, Gypsum or Selenite?
They are about equally hard, both near Mohs 2.
Which is more valuable, Gypsum or Selenite?
Typical specimens of Gypsum and Selenite trade in a similar range, around $20.
