Comparison · Minerals
Anhydrite vs Satin Spar
Anhydrite and Satin Spar are easy to confuse because both are minerals. Anhydrite is harder (Mohs 3–3.5) than Satin Spar (Mohs 2), so Anhydrite will scratch Satin Spar 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 Satin Spar
- Anhydrite is harder (Mohs 3–3.5) than Satin Spar (Mohs 2), so Anhydrite will scratch Satin Spar and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
- Luster is different: Anhydrite is vitreous, pearly on cleavage surfaces while Satin Spar is silky.
- Anhydrite feels noticeably heavier for its size (specific gravity 2.9–3.0 versus 2.3 for Satin Spar).
- Hold a thin edge to the light: Anhydrite is Transparent to translucent, Satin Spar is translucent.
- They overlap in clear and pink, but Anhydrite also comes in gray and blue.
- Well-formed crystals give it away: Anhydrite is Orthorhombic, Satin Spar is monoclinic.
Anhydrite vs Satin Spar properties
| Property | Anhydrite | Satin Spar |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 3–3.5 | 2 |
| Luster | Vitreous, pearly on cleavage surfaces | silky |
| Streak | White | White |
| Transparency | Transparent to translucent | translucent |
| Specific gravity | 2.9–3.0 | 2.3 |
| Crystal system | Orthorhombic | monoclinic |
| Common colors | Colorless, White, Gray, Blue, Pink | White, Cream, Colorless, Peach |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $5–$120+ |
Which is more valuable?
Typical specimens of Anhydrite and Satin Spar trade in a similar range, around $20.
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 Satin Spar
Satin Spar is a fibrous variety of gypsum recognized by its silky sheen, white to cream color, and soft hardness.
Anhydrite vs Satin Spar FAQ
Is Anhydrite the same as Satin Spar?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Anhydrite is harder (Mohs 3–3.5) than Satin Spar (Mohs 2), so Anhydrite will scratch Satin Spar and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
How can you tell Anhydrite from Satin Spar?
Anhydrite is harder (Mohs 3–3.5) than Satin Spar (Mohs 2), so Anhydrite will scratch Satin Spar and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Luster is different: Anhydrite is vitreous, pearly on cleavage surfaces while Satin Spar is silky. Anhydrite feels noticeably heavier for its size (specific gravity 2.9–3.0 versus 2.3 for Satin Spar).
Which is harder, Anhydrite or Satin Spar?
Anhydrite is harder: Mohs 3–3.5 against Mohs 2 for Satin Spar.
Which is more valuable, Anhydrite or Satin Spar?
Typical specimens of Anhydrite and Satin Spar trade in a similar range, around $20.
