Comparison · Sedimentary Rocks vs Minerals
Evaporite vs Gypsum
Evaporite and Gypsum are easy to confuse. Both sit near Mohs 2.5, 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 Evaporite and Gypsum
- Both sit near Mohs 2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Luster is different: Evaporite is dull while Gypsum is vitreous, pearly, or silky (fibrous), earthy when massive.
- Hold a thin edge to the light: Evaporite is opaque, Gypsum is Transparent to translucent.
- They overlap in clear, pink, gray, and brown, but Gypsum also comes in yellow.
Evaporite vs Gypsum properties
| Property | Evaporite | Gypsum |
|---|---|---|
| Type | Sedimentary Rocks | Minerals |
| Mohs hardness | 2.5 | 2 |
| Luster | dull | Vitreous, pearly, or silky (fibrous), earthy when massive |
| Streak | White | White |
| Transparency | opaque | Transparent to translucent |
| Specific gravity | 2.2 | 2.3–2.35 |
| Crystal system | varies | Monoclinic |
| Common colors | White, Clear, Pink, Gray, Tan | Colorless, White, Gray, Yellow, Brown, Pink |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $2–$150+ |
Which is more valuable?
Gypsum is usually the more valuable of the two: a typical collector specimen runs about $20 against $10 for Evaporite, and premium Gypsum can reach $150 or more.
About Evaporite
Evaporite is a sedimentary rock or deposit formed by evaporation of mineral-rich water, commonly containing rock salt, gypsum, or anhydrite.
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.
Evaporite vs Gypsum FAQ
Is Evaporite the same as Gypsum?
No. Evaporite is a sedimentary rock while Gypsum is a mineral. Both sit near Mohs 2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Evaporite from Gypsum?
Both sit near Mohs 2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Luster is different: Evaporite is dull while Gypsum is vitreous, pearly, or silky (fibrous), earthy when massive. Hold a thin edge to the light: Evaporite is opaque, Gypsum is Transparent to translucent.
Which is harder, Evaporite or Gypsum?
Evaporite is harder: Mohs 2.5 against Mohs 2 for Gypsum.
Which is more valuable, Evaporite or Gypsum?
Gypsum is usually the more valuable of the two: a typical collector specimen runs about $20 against $10 for Evaporite, and premium Gypsum can reach $150 or more.
