Comparison · Minerals
Atacamite vs Calcite
Atacamite and Calcite 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 Atacamite and Calcite
- Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Atacamite leaves a apple green streak on unglazed porcelain, Calcite leaves white.
- Atacamite feels noticeably heavier for its size (specific gravity 3.75–3.77 versus 2.7 for Calcite).
- Hold a thin edge to the light: Atacamite is Transparent to translucent, Calcite is transparent.
- They overlap in green, but Calcite also comes in clear, yellow, orange, blue, and pink.
- Well-formed crystals give it away: Atacamite is Orthorhombic, Calcite is trigonal.
Atacamite vs Calcite properties
| Property | Atacamite | Calcite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 3–3.5 | 3 |
| Luster | Vitreous to adamantine | vitreous |
| Streak | Apple green | White |
| Transparency | Transparent to translucent | transparent |
| Specific gravity | 3.75–3.77 | 2.7 |
| Crystal system | Orthorhombic | trigonal |
| Common colors | Bright green, Dark green | Colorless, White, Yellow, Orange, Blue, Green, Pink |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$100+ |
Which is more valuable?
Atacamite is usually the more valuable of the two: a typical collector specimen runs about $20 against $15 for Calcite, and premium Atacamite can reach $150 or more.
About Atacamite
Atacamite is a copper chloride hydroxide mineral, Cu2Cl(OH)3, that forms a striking emerald to blackish-green secondary mineral in the oxidized zones of copper deposits. It takes its name from the Atacama Desert of Chile, where it was first described and where arid conditions allow chloride-bearing copper minerals to persist rather than being washed away. Atacamite is notable among copper minerals for containing structural chlorine, which ties its formation to saline or coastal environments.
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.
Atacamite vs Calcite FAQ
Is Atacamite the same as Calcite?
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 Atacamite from Calcite?
Both sit near Mohs 3–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Atacamite leaves a apple green streak on unglazed porcelain, Calcite leaves white. Atacamite feels noticeably heavier for its size (specific gravity 3.75–3.77 versus 2.7 for Calcite).
Which is harder, Atacamite or Calcite?
They are about equally hard, both near Mohs 3–3.5.
Which is more valuable, Atacamite or Calcite?
Atacamite is usually the more valuable of the two: a typical collector specimen runs about $20 against $15 for Calcite, and premium Atacamite can reach $150 or more.
