Calcite vs Wollastonite
| Property | Calcite | Wollastonite |
|---|---|---|
| Formula | CaCO3 | CaSiO3 |
| Crystal System | Trigonal | Triclinic |
| Mineral Class | 05 Carbonates and Nitrates | 09 Silicates |
| Mohs Hardness | 3.0 | 4.5-5.0 |
| Color | Colorless, white, yellow, orange, blue, green | White, gray, very pale green |
| Luster | Vitreous | Vitreous |
| Streak | White | White |
| Transparency | Transparent | Translucent |
| Cleavage | Perfect rhombohedral {1011} | Perfect {100} |
| Fracture | Conchoidal | Uneven |
Key Differences
- ◆ Wollastonite (CaSiO3) is formed by metamorphic reaction of calcite with quartz: CaCO3 + SiO2 → CaSiO3 + CO2.
- ◆ Wollastonite does not react with HCl; calcite effervesces vigorously.
- ◆ Wollastonite (hardness 4.5–5) is harder than calcite (hardness 3).
- ◆ Wollastonite is white to pale gray with vitreous to silky luster; calcite is highly variable in color.
- ◆ Wollastonite is industrially used as a ceramic filler; calcite is used in lime production.