Comparison · Minerals
Anhydrite vs Fluorite
Anhydrite and Fluorite are easy to confuse because both are minerals. Both sit near Mohs 3–3.5, 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 Anhydrite and Fluorite
- Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Anhydrite is Transparent to translucent, Fluorite is transparent.
- They overlap in clear, blue, and pink, but Anhydrite also comes in gray and Fluorite also comes in purple, green, and yellow.
- Well-formed crystals give it away: Anhydrite is Orthorhombic, Fluorite is cubic.
Anhydrite vs Fluorite properties
| Property | Anhydrite | Fluorite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 3–3.5 | 4 |
| Luster | Vitreous, pearly on cleavage surfaces | vitreous |
| Streak | White | White |
| Transparency | Transparent to translucent | transparent |
| Specific gravity | 2.9–3.0 | 3.2 |
| Crystal system | Orthorhombic | cubic |
| Common colors | Colorless, White, Gray, Blue, Pink | Purple, Green, Blue, Yellow, Colorless, Pink |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $5–$200+ |
Which is more valuable?
Fluorite is usually the more valuable of the two: a typical collector specimen runs about $25 against $20 for Anhydrite, and premium Fluorite can reach $200 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 Fluorite
Fluorite is a colorful mineral that often exhibits multiple colors in a single specimen. It's the defining mineral for 4 on the Mohs hardness scale.
Anhydrite vs Fluorite FAQ
Is Anhydrite the same as Fluorite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Anhydrite from Fluorite?
Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Anhydrite is Transparent to translucent, Fluorite is transparent. They overlap in clear, blue, and pink, but Anhydrite also comes in gray and Fluorite also comes in purple, green, and yellow.
Which is harder, Anhydrite or Fluorite?
Fluorite is harder: Mohs 4 against Mohs 3–3.5 for Anhydrite.
Which is more valuable, Anhydrite or Fluorite?
Fluorite is usually the more valuable of the two: a typical collector specimen runs about $25 against $20 for Anhydrite, and premium Fluorite can reach $200 or more.
