Comparison · Minerals vs Silicate Minerals
Calcite vs Zoisite
Calcite and Zoisite are easy to confuse. Zoisite is harder (Mohs 6.5) than Calcite (Mohs 3), so Zoisite will scratch Calcite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Calcite and Zoisite
- Zoisite is harder (Mohs 6.5) than Calcite (Mohs 3), so Zoisite will scratch Calcite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
- Zoisite feels noticeably heavier for its size (specific gravity 3.3 versus 2.7 for Calcite).
- They overlap in blue, green, and pink, but Calcite also comes in clear, yellow, and orange and Zoisite also comes in gray.
- Well-formed crystals give it away: Calcite is trigonal, Zoisite is orthorhombic.
Calcite vs Zoisite properties
| Property | Calcite | Zoisite |
|---|---|---|
| Type | Minerals | Silicate Minerals |
| Mohs hardness | 3 | 6.5 |
| Luster | vitreous | vitreous |
| Streak | White | White |
| Transparency | transparent | transparent |
| Specific gravity | 2.7 | 3.3 |
| Crystal system | trigonal | orthorhombic |
| Common colors | Colorless, White, Yellow, Orange, Blue, Green, Pink | Green, Pink, Blue, Gray |
| Rarity | common | uncommon |
| Typical specimen value | $2–$100+ | $12–$450+ |
Which is more valuable?
Zoisite is usually the more valuable of the two: a typical collector specimen runs about $70 against $15 for Calcite, and premium Zoisite can reach $450 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 Zoisite
Zoisite is a calcium aluminum silicate that occurs in striated prismatic crystals and massive aggregates. Best known through its blue-violet gem variety tanzanite and the pink variety thulite, it is both a metamorphic mineral and a notable gemstone.
Calcite vs Zoisite FAQ
Is Calcite the same as Zoisite?
No. Calcite is a mineral while Zoisite is a silicate mineral. Zoisite is harder (Mohs 6.5) than Calcite (Mohs 3), so Zoisite will scratch Calcite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
How can you tell Calcite from Zoisite?
Zoisite is harder (Mohs 6.5) than Calcite (Mohs 3), so Zoisite will scratch Calcite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Zoisite feels noticeably heavier for its size (specific gravity 3.3 versus 2.7 for Calcite). They overlap in blue, green, and pink, but Calcite also comes in clear, yellow, and orange and Zoisite also comes in gray.
Which is harder, Calcite or Zoisite?
Zoisite is harder: Mohs 6.5 against Mohs 3 for Calcite.
Which is more valuable, Calcite or Zoisite?
Zoisite is usually the more valuable of the two: a typical collector specimen runs about $70 against $15 for Calcite, and premium Zoisite can reach $450 or more.
