Calcite vs Fluorite
| Property | Calcite | Fluorite |
|---|---|---|
| Formula | CaCO3 | CaF2 |
| Crystal System | Trigonal | Cubic (Isometric) |
| Mineral Class | 05 Carbonates and Nitrates | 03 Halides |
| Mohs Hardness | 3.0 | 4.0 |
| Color | Colorless, white, yellow, orange, blue, green | Purple, blue, green, yellow, colorless, pink |
| Luster | Vitreous | Vitreous |
| Streak | White | White |
| Transparency | Transparent | Transparent |
| Cleavage | Perfect rhombohedral {1011} | Perfect octahedral {111} |
| Fracture | Conchoidal | Conchoidal |
Key Differences
- ◆ Calcite (hardness 3) is scratched by a copper coin; fluorite (hardness 4) requires a steel knife to scratch.
- ◆ Calcite reacts vigorously with dilute HCl; fluorite does not react with HCl.
- ◆ Fluorite has perfect octahedral cleavage (4 directions); calcite has perfect rhombohedral cleavage (3 directions).
- ◆ Fluorite (CaF2) is a halide; calcite (CaCO3) is a carbonate.
- ◆ Fluorite fluoresces under UV light (phenomenon named after it); calcite rarely fluoresces.