Hardness Scale

Gemstones and other minerals are ranked according to their hardness.  Hardness refers to a stone's ability to resist abrasion.  A hard gemstone is not automatically tough or durable.

The Mohs scale of hardness is the most common method used to rank gemstones according to hardness.  Devised by German mineralogist Friedrich Mohs in 1812, this scale grades minerals on a scale from 1 (very soft) to 10 (very hard). 

The Mohs scale is a relative scale, for example, diamond (10) is about 4-5 times harder than corundum (9), which is about 2 times harder than topaz (8). 

A gem with a given hardness rating will scratch other gems of the same hardness and all gems with lower hardness ratings.  Gold, silver, and platinum are all relatively soft, with Mohs ratings between 2.5-4.