Comparison · Minerals vs Halide Minerals
Gypsum vs Sylvite
Gypsum and Sylvite are easy to confuse. 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 Sylvite
- 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, Sylvite is transparent.
- They overlap in clear and pink, but Gypsum also comes in gray, yellow, and brown and Sylvite also comes in red.
- Well-formed crystals give it away: Gypsum is Monoclinic, Sylvite is cubic.
Gypsum vs Sylvite properties
| Property | Gypsum | Sylvite |
|---|---|---|
| Type | Minerals | Halide 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 | 1.99 |
| Crystal system | Monoclinic | cubic |
| Common colors | Colorless, White, Gray, Yellow, Brown, Pink | Colorless, White, Red, Pink, Bluish |
| Rarity | common | uncommon |
| Typical specimen value | $2–$150+ | $5–$180+ |
Which is more valuable?
Sylvite is usually the more valuable of the two: a typical collector specimen runs about $30 against $20 for Gypsum, and premium Sylvite can reach $180 or more.
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 Sylvite
Sylvite is potassium chloride, a soft evaporite mineral closely resembling halite. It forms cubic crystals and granular masses in salt deposits and is the principal ore mineral for potassium used in fertilizer.
Gypsum vs Sylvite FAQ
Is Gypsum the same as Sylvite?
No. Gypsum is a mineral while Sylvite is a halide mineral. 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 Sylvite?
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, Sylvite is transparent. They overlap in clear and pink, but Gypsum also comes in gray, yellow, and brown and Sylvite also comes in red.
Which is harder, Gypsum or Sylvite?
They are about equally hard, both near Mohs 2.
Which is more valuable, Gypsum or Sylvite?
Sylvite is usually the more valuable of the two: a typical collector specimen runs about $30 against $20 for Gypsum, and premium Sylvite can reach $180 or more.
