Comparison · Minerals
Alabaster vs Anhydrite
Alabaster and Anhydrite are easy to confuse because both are minerals. Anhydrite is harder (Mohs 3–3.5) than Alabaster (Mohs 1.5–2), so Anhydrite will scratch Alabaster 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 Alabaster and Anhydrite
- Anhydrite is harder (Mohs 3–3.5) than Alabaster (Mohs 1.5–2), so Anhydrite will scratch Alabaster 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 2.3 for Alabaster).
- Hold a thin edge to the light: Alabaster is Translucent to opaque, Anhydrite is Transparent to translucent.
- They overlap in pink and gray, but Alabaster also comes in white, yellow, and multicolored and Anhydrite also comes in clear and blue.
- Well-formed crystals give it away: Alabaster is Monoclinic, Anhydrite is Orthorhombic.
Alabaster vs Anhydrite properties
| Property | Alabaster | Anhydrite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 1.5–2 | 3–3.5 |
| Luster | Vitreous (crystalline); waxy to dull (massive) | Vitreous, pearly on cleavage surfaces |
| Streak | White | White |
| Transparency | Translucent to opaque | Transparent to translucent |
| Specific gravity | 2.3 | 2.9–3.0 |
| Crystal system | Monoclinic | Orthorhombic |
| Common colors | White, Cream, Pale pink, Yellowish, Gray, Banded | Colorless, White, Gray, Blue, Pink |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Alabaster and Anhydrite trade in a similar range, around $20.
About Alabaster
Alabaster is a fine-grained, massive variety of gypsum (calcium sulfate dihydrate, CaSO4·2H2O), prized since antiquity for carving because of its softness and ability to take a smooth polish. Unlike crystalline selenite, alabaster shows no visible crystal faces, appearing instead as a compact, sugary or waxy mass. Its low hardness and solubility in water set it apart from harder ornamental stones like marble, which it is often confused with by name alone.
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.
Alabaster vs Anhydrite FAQ
Is Alabaster the same as Anhydrite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Anhydrite is harder (Mohs 3–3.5) than Alabaster (Mohs 1.5–2), so Anhydrite will scratch Alabaster and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
How can you tell Alabaster from Anhydrite?
Anhydrite is harder (Mohs 3–3.5) than Alabaster (Mohs 1.5–2), so Anhydrite will scratch Alabaster 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 2.3 for Alabaster). Hold a thin edge to the light: Alabaster is Translucent to opaque, Anhydrite is Transparent to translucent.
Which is harder, Alabaster or Anhydrite?
Anhydrite is harder: Mohs 3–3.5 against Mohs 1.5–2 for Alabaster.
Which is more valuable, Alabaster or Anhydrite?
Typical specimens of Alabaster and Anhydrite trade in a similar range, around $20.
