- 2062 Baisakh (old course) · 2 marks
Hardness versus strength
Short answer
Hardness is a mineral’s resistance to scratching, measured on the Mohs scale (e.g., quartz 7). Strength is a rock’s ability to resist load without failure, measured in MPa; it depends on mineral type, texture, cementation, and joints. A hard mineral does not ensure a strong rock.
Differentiate between hardness and strength.
| Basis | Hardness | Strength |
|---|---|---|
| Meaning | Resistance to scratching or abrasion | Ability to resist load without failing |
| Applies to | Minerals mainly | Rocks and soils |
| Measurement | Mohs scale (1-10) | Compressive, tensile or shear strength (MPa) |
| Test | Scratch test | Uniaxial compression, point load tests |
| Depends on | Bond strength of minerals | Mineral type, texture, cementation, pores, joints, weathering |
| Nature | Surface property, relative | Bulk property, absolute |
| Example | Quartz = 7 | Granite: about 100-250 MPa |
A hard mineral does not always mean a strong rock; a quartz-rich but weakly cemented sandstone has low strength.
✓ Answer checked by Claude Opus 5.5 (high effort)
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