Mohs Hardness

Friedrich Mohs, an Austrian Mineralogist, born on January 29, 1773 and died on December 29, 1839 (source Wikipedia) found a relatively simple answer to measure the hardness of Minerals.
He designed a Hardness Scale, based on the least hard, naturally occurring mineral Talc, which he ascribed a value of 1. Talc, can be scratched by any other mineral. To Diamond, the hardest naturally occurring mineral, he ascribed a value of 10. Only Diamond can be scratched, by Diamond.

Mohs Industrial Hardness Test Set
€ 149.95