Comparison · Minerals vs Halide Minerals
Anhydrite vs Sylvite
Anhydrite and Sylvite are easy to confuse. Anhydrite is harder (Mohs 3–3.5) than Sylvite (Mohs 2), so Anhydrite will scratch Sylvite and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Anhydrite and Sylvite
- Anhydrite is harder (Mohs 3–3.5) than Sylvite (Mohs 2), so Anhydrite will scratch Sylvite and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
- Anhydrite feels noticeably heavier for its size (specific gravity 2.9–3.0 versus 1.99 for Sylvite).
- Hold a thin edge to the light: Anhydrite is Transparent to translucent, Sylvite is transparent.
- They overlap in clear and pink, but Anhydrite also comes in gray and blue and Sylvite also comes in red.
- Well-formed crystals give it away: Anhydrite is Orthorhombic, Sylvite is cubic.
Anhydrite vs Sylvite properties
| Property | Anhydrite | Sylvite |
|---|---|---|
| Type | Minerals | Halide Minerals |
| Mohs hardness | 3–3.5 | 2 |
| Luster | Vitreous, pearly on cleavage surfaces | vitreous |
| Streak | White | White |
| Transparency | Transparent to translucent | transparent |
| Specific gravity | 2.9–3.0 | 1.99 |
| Crystal system | Orthorhombic | cubic |
| Common colors | Colorless, White, Gray, Blue, 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 Anhydrite, and premium Sylvite can reach $180 or more.
About Anhydrite
Anhydrite is calcium sulfate, CaSO4, chemically identical to gypsum but lacking the water molecules bound into gypsum's crystal structure. It forms in evaporite basins where seawater or saline lake water concentrates through evaporation, and it readily absorbs water to convert into gypsum, which is why anhydrite outcrops are less common at the surface than at depth. Its name, from the Greek for "without water," directly references this dehydrated composition.
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.
Anhydrite vs Sylvite FAQ
Is Anhydrite the same as Sylvite?
No. Anhydrite is a mineral while Sylvite is a halide mineral. Anhydrite is harder (Mohs 3–3.5) than Sylvite (Mohs 2), so Anhydrite will scratch Sylvite and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
How can you tell Anhydrite from Sylvite?
Anhydrite is harder (Mohs 3–3.5) than Sylvite (Mohs 2), so Anhydrite will scratch Sylvite and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Anhydrite feels noticeably heavier for its size (specific gravity 2.9–3.0 versus 1.99 for Sylvite). Hold a thin edge to the light: Anhydrite is Transparent to translucent, Sylvite is transparent.
Which is harder, Anhydrite or Sylvite?
Anhydrite is harder: Mohs 3–3.5 against Mohs 2 for Sylvite.
Which is more valuable, Anhydrite or Sylvite?
Sylvite is usually the more valuable of the two: a typical collector specimen runs about $30 against $20 for Anhydrite, and premium Sylvite can reach $180 or more.
