Mohs Gemstone Ranking
The Mohs ranking refers to the material's ability to resist abrasion or scratching. Mohs uses a scale of 1 to 10. One being the softest and ten the hardest. Non gemstones such as pearls coral and jet are also ranked by jewelers using the Mohs Ranking.
A diamond would be rated a ten and a four would be Rhodochrosite (also known as a Inca Rose Stone).
THE MOHS RANKING SYSTEM WAS DEVISED BY A GERMAN MINERALOGIST NAMED FRIEMRICH MOH IN 1812