Corundum vs Diamond
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| Property | Corundum | Diamond |
|---|---|---|
| Formel | Al2O3 | C |
| Kristallsystem | Trigonal | Cubic (Isometric) |
| Mineralklasse | 04 Oxides and Hydroxides | 01 Native Elements |
| Mohshärte | 9.0 | 10.0 |
| Farbe | Red (ruby), blue (sapphire), various colors | Colorless, yellow, brown, blue, green, pink |
| Glanz | Adamantine | Adamantine |
| Strichfarbe | Colorless | None |
| Transparenz | Transparent | Transparent |
| Spaltbarkeit | None | Perfect octahedral {111} |
| Bruch | Conchoidal to uneven | Conchoidal |
Key Differences
- ◆ Diamond (hardness 10) is harder than corundum (hardness 9) — the hardest natural mineral vs. the second hardest.
- ◆ Diamond is pure carbon; corundum is aluminum oxide (Al2O3).
- ◆ Diamond crystallises in the cubic system; corundum is trigonal.
- ◆ Both are used as abrasives, but diamond abrades corundum, not vice versa.
- ◆ Corundum gem varieties are ruby and sapphire; diamond gems are simply called diamonds.