Created in 1812 by Austrian mineralogist Friedrich Mohs, the Mohs scale remains the reference tool for assessing mineral hardness. Its principle is one of elegant simplicity: a harder mineral will always scratch a softer one, but never the reverse.
The Principle of the Scale
Mohs selected ten representative minerals, from softest to hardest, to form his reference scale. Each mineral can scratch all those below it, but will leave no mark on those above.
The Ten Minerals of the Scale
1. Talc — so soft it can be scratched by a fingernail
2. Gypsum — scratched by a fingernail
3. Calcite — scratched by a coin
4. Fluorite
5. Apatite — scratched by a knife
6. Feldspar — scratches glass
7. Quartz — easily scratches glass
8. Topaz
9. Corundum (sapphire, ruby)
10. Diamond — the hardest of all
Diamond at the Absolute Summit
The score of 10 awarded to diamond reflects an extraordinary reality: diamond is the hardest naturally occurring material in existence. It easily scratches talc, quartz, sapphire — and every other known mineral. Nothing can scratch it, except another diamond.
This incomparable hardness is why diamond has been used in cutting and drilling tools for centuries, long before becoming the symbol of fine jewellery. It is also what guarantees the longevity of a diamond jewel: properly cared for, it will last for generations.
Lab-grown diamonds display exactly the same hardness as natural diamonds. Composed of the same carbon crystallised in a cubic lattice, they also achieve the score of 10 on the Mohs scale — absolute perfection.