Quartz vs Calcite
A classic hardness and acid-reaction distinction.
| Property | Quartz | Calcite |
|---|---|---|
| Category | minerals | minerals |
| Group | Silicate | Carbonate |
| Class | Silicates | Carbonates |
| Chemical formula | SiO2 | CaCO3 |
| Crystal system | Trigonal | Trigonal |
| Mohs hardness | 7 | 3 |
| Specific gravity | 2.65 | 2.71 |
| Colour | Colourless, white, purple, pink, brown, black | Colourless, white, many tints |
| Streak | White | White |
| Luster | Vitreous | Vitreous |
| Transparency | Transparent to translucent | Transparent to translucent |
| Formation environment | Igneous, metamorphic and sedimentary environments | Sedimentary limestones, hydrothermal veins |
| Common uses | Glass, electronics, abrasives | Cement, optical calcite (historically) |