Comparison · Minerals
Anhydrite vs Selenite
Anhydrite and Selenite are easy to confuse because both are minerals. Anhydrite is harder (Mohs 3–3.5) than Selenite (Mohs 2), so Anhydrite will scratch Selenite 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 Selenite
- Anhydrite is harder (Mohs 3–3.5) than Selenite (Mohs 2), so Anhydrite will scratch Selenite 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 Selenite).
- Hold a thin edge to the light: Anhydrite is Transparent to translucent, Selenite is transparent.
- They overlap in clear, gray, and pink, but Anhydrite also comes in blue.
- Well-formed crystals give it away: Anhydrite is Orthorhombic, Selenite is monoclinic.
Anhydrite vs Selenite properties
| Property | Anhydrite | Selenite |
|---|---|---|
| Type | Minerals | 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 | 2.3 |
| Crystal system | Orthorhombic | monoclinic |
| Common colors | Colorless, White, Gray, Blue, Pink | Colorless, White, Peach, Gray |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $5–$150+ |
Which is more valuable?
Typical specimens of Anhydrite and Selenite 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 Selenite
Selenite is a crystalline form of gypsum known for its transparency and moon-like glow. The Cave of Crystals in Mexico contains selenite crystals up to 12 meters long.
Anhydrite vs Selenite FAQ
Is Anhydrite the same as Selenite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Anhydrite is harder (Mohs 3–3.5) than Selenite (Mohs 2), so Anhydrite will scratch Selenite and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
How can you tell Anhydrite from Selenite?
Anhydrite is harder (Mohs 3–3.5) than Selenite (Mohs 2), so Anhydrite will scratch Selenite 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 Selenite). Hold a thin edge to the light: Anhydrite is Transparent to translucent, Selenite is transparent.
Which is harder, Anhydrite or Selenite?
Anhydrite is harder: Mohs 3–3.5 against Mohs 2 for Selenite.
Which is more valuable, Anhydrite or Selenite?
Typical specimens of Anhydrite and Selenite trade in a similar range, around $20.
