Comparison · Minerals
Calcite vs Gypsum
Calcite and Gypsum are easy to confuse because both are minerals. Calcite is harder (Mohs 3) than Gypsum (Mohs 2), so Calcite will scratch Gypsum 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 Calcite and Gypsum
- Calcite is harder (Mohs 3) than Gypsum (Mohs 2), so Calcite will scratch Gypsum and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
- Hold a thin edge to the light: Calcite is transparent, Gypsum is Transparent to translucent.
- They overlap in clear, yellow, and pink, but Calcite also comes in orange, blue, and green and Gypsum also comes in gray and brown.
- Well-formed crystals give it away: Calcite is trigonal, Gypsum is Monoclinic.
Calcite vs Gypsum properties
| Property | Calcite | Gypsum |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 3 | 2 |
| Luster | vitreous | Vitreous, pearly, or silky (fibrous), earthy when massive |
| Streak | White | White |
| Transparency | transparent | Transparent to translucent |
| Specific gravity | 2.7 | 2.3–2.35 |
| Crystal system | trigonal | Monoclinic |
| Common colors | Colorless, White, Yellow, Orange, Blue, Green, Pink | Colorless, White, Gray, Yellow, Brown, Pink |
| Rarity | common | common |
| Typical specimen value | $2–$100+ | $2–$150+ |
Which is more valuable?
Gypsum is usually the more valuable of the two: a typical collector specimen runs about $20 against $15 for Calcite, and premium Gypsum can reach $150 or more.
About Calcite
Calcite is one of the most common minerals on Earth, found in sedimentary, metamorphic, and igneous rocks. It's the primary component of limestone and marble.
About Gypsum
Gypsum is a soft, common evaporite mineral, calcium sulfate dihydrate with the formula CaSO4·2H2O, that defines hardness 2 on the Mohs scale and can be scratched with a fingernail. It precipitates from evaporating saline water and occurs in forms ranging from transparent selenite crystals to fibrous satin spar and massive alabaster. Gypsum is also the principal raw material used to manufacture plaster of Paris and drywall.
Calcite vs Gypsum FAQ
Is Calcite the same as Gypsum?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Calcite is harder (Mohs 3) than Gypsum (Mohs 2), so Calcite will scratch Gypsum and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
How can you tell Calcite from Gypsum?
Calcite is harder (Mohs 3) than Gypsum (Mohs 2), so Calcite will scratch Gypsum and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Hold a thin edge to the light: Calcite is transparent, Gypsum is Transparent to translucent. They overlap in clear, yellow, and pink, but Calcite also comes in orange, blue, and green and Gypsum also comes in gray and brown.
Which is harder, Calcite or Gypsum?
Calcite is harder: Mohs 3 against Mohs 2 for Gypsum.
Which is more valuable, Calcite or Gypsum?
Gypsum is usually the more valuable of the two: a typical collector specimen runs about $20 against $15 for Calcite, and premium Gypsum can reach $150 or more.
