Comparison · Minerals
Calcite vs Gibbsite
Calcite and Gibbsite are easy to confuse because both are minerals. Both sit near Mohs 3, 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 Calcite and Gibbsite
- Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Calcite is transparent, Gibbsite is Transparent to translucent.
- They overlap in green, but Calcite also comes in clear, yellow, orange, blue, and pink and Gibbsite also comes in white, gray, and red.
- Well-formed crystals give it away: Calcite is trigonal, Gibbsite is Monoclinic.
Calcite vs Gibbsite properties
| Property | Calcite | Gibbsite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 3 | 2.5–3.5 |
| Luster | vitreous | Vitreous, pearly on cleavage, dull when earthy |
| Streak | White | White |
| Transparency | transparent | Transparent to translucent |
| Specific gravity | 2.7 | 2.3–2.4 |
| Crystal system | trigonal | Monoclinic |
| Common colors | Colorless, White, Yellow, Orange, Blue, Green, Pink | White, Gray, Greenish, Reddish |
| Rarity | common | common |
| Typical specimen value | $2–$100+ | $2–$150+ |
Which is more valuable?
Gibbsite is usually the more valuable of the two: a typical collector specimen runs about $20 against $15 for Calcite, and premium Gibbsite 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 Gibbsite
Gibbsite is aluminum hydroxide, Al(OH)3, a soft, typically white to gray mineral that forms as a weathering product in tropical and subtropical soils and serves as the principal ore mineral of aluminum within bauxite deposits. It commonly occurs as fine-grained, earthy masses or crusts rather than well-formed crystals, though occasional tabular pseudohexagonal crystals do develop in cavities. It is named after American mineral collector George Gibbs, whose collection helped found early American mineralogy.
Calcite vs Gibbsite FAQ
Is Calcite the same as Gibbsite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Calcite from Gibbsite?
Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Calcite is transparent, Gibbsite is Transparent to translucent. They overlap in green, but Calcite also comes in clear, yellow, orange, blue, and pink and Gibbsite also comes in white, gray, and red.
Which is harder, Calcite or Gibbsite?
They are about equally hard, both near Mohs 3.
Which is more valuable, Calcite or Gibbsite?
Gibbsite is usually the more valuable of the two: a typical collector specimen runs about $20 against $15 for Calcite, and premium Gibbsite can reach $150 or more.
