Mohs Scale

The Mohs Scale designates the comparative hardness of various natural minerals. The scale runs from 1 (very soft) to 10 (very hard). A diamond, the hardest substance known to man, is the only mineral that is rated 10. This means that it is extremely resistant to scratches or abrasions. Rubies and sapphires are rated 9, and other semi precious gems are rated from 7-8.