- 2063 Baisakh (old course) · 2 marks
Calcite versus quartz
Short answer
Calcite is CaCO₃, hardness 3, perfect rhombohedral cleavage, effervesces in HCl, and dissolves in acidic water. Quartz is SiO₂, hardness 7, no cleavage, conchoidal fracture, no acid reaction, and is highly resistant to weathering.
Differentiate between calcite and quartz.
| Basis | Calcite | Quartz |
|---|---|---|
| Composition | Calcium carbonate, CaCO₃ | Silica, SiO₂ |
| Hardness | 3 | 7 |
| Cleavage | Perfect, three directions (rhombohedral) | None; conchoidal fracture |
| HCl test | Effervescence | No reaction |
| Crystal system | Trigonal | Trigonal (hexagonal group) |
| Specific gravity | 2.71 | 2.65 |
| Weathering | Dissolves in acidic water | Highly resistant |
| Occurs in | Limestone, marble | Granite, sandstone, quartzite |
✓ Answer checked by Claude Opus 5.5 (high effort)
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