Corundum vs Silicon carbide
Corundum and Silicon carbide are genuine alternatives to one another — a choice somebody actually makes — and differ on 3 measured properties, crystal system most clearly.
Corundum vs Silicon carbide
These are different kinds of thing (mineral, compound). Fewer properties mean the same thing across both, so a like-for-like reading may not be available.
Corundum
Al2O3
Aluminium oxide — hardness 9, the mineral of ruby and sapphire, and a major industrial abrasive.
Silicon carbide
SiC
A synthetic ceramic close to diamond in hardness, and the first commercially successful manufactured abrasive.
| Property | Corundum | Silicon carbide |
|---|---|---|
| Crystal system Categorical values can be listed side by side but not ordered or subtracted. | trigonal | hexagonal |
| Density | 3.95–4.1 g/cm³ higher | 3.21 g/cm³ |
| Lustre Only one of the two has a figure we can stand behind, so there is nothing to compare. | vitreous to adamantine | Not known |
| Mohs hardness Mohs hardness is an ordinal scale: values can be ranked, but differences and ratios between them are not meaningful. | 9 | 9–9.5 higher |
| Molar mass Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 40.1 g/mol |
Choosing between them
Silicon carbide is recorded as a substitute for Corundum — stronger.
What it gives up: More friable, so a grain breaks down faster and the wheel wears.
Direct substitute, on the evidence cited above.