Asked by big gieger
How hard is a diamond
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Very hard — diamond is the hardest naturally occurring mineral. On the common Mohs hardness scale it is a 10 (the top of the scale), meaning it can scratch every other mineral.
A few clarifications and numbers:
- Mohs = 10: this is a relative, qualitative scale based on scratch resistance.
- Instrumented hardness (quantitative) depends on test and orientation. Typical Vickers hardness values for single-crystal diamond are on the order of 70–150 GPa (nanoindentation and microindentation results vary with load and crystallographic direction). Knoop hardness values are often reported in the range of roughly 7,000–12,000 kgf/mm².
- Hardness is different from toughness (resistance to fracture). Diamond is extremely hard (resists scratching) but can be brittle and has easy cleavage planes, so it can chip or split if struck along those planes.
- The extreme hardness comes from the strong sp3 covalent bonding in the tetrahedral carbon lattice.
Practical consequences: diamonds are used for cutting, grinding, drilling and polishing because they scratch or abrade almost anything. The only common materials that can cut or abrade diamond are other diamonds and a few engineered superhard materials (cubic boron nitride and some specialized synthesized forms reported in research).
A few clarifications and numbers:
- Mohs = 10: this is a relative, qualitative scale based on scratch resistance.
- Instrumented hardness (quantitative) depends on test and orientation. Typical Vickers hardness values for single-crystal diamond are on the order of 70–150 GPa (nanoindentation and microindentation results vary with load and crystallographic direction). Knoop hardness values are often reported in the range of roughly 7,000–12,000 kgf/mm².
- Hardness is different from toughness (resistance to fracture). Diamond is extremely hard (resists scratching) but can be brittle and has easy cleavage planes, so it can chip or split if struck along those planes.
- The extreme hardness comes from the strong sp3 covalent bonding in the tetrahedral carbon lattice.
Practical consequences: diamonds are used for cutting, grinding, drilling and polishing because they scratch or abrade almost anything. The only common materials that can cut or abrade diamond are other diamonds and a few engineered superhard materials (cubic boron nitride and some specialized synthesized forms reported in research).
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