What is a Mohs Scale - The Definition

A scale of relative hardness for use in testing minerals. Named for the German mineralogist Friedrich Mohs [1772-1839], who proposed it in 1822

The minerals are numbered but the intervals between them are very different, and diamond is far harder than corundum (sapphires and rubies) as much harder than corundum is harder than talc.

The scale is:

1 Talc         | 2 Gypsum | 3 Calcite  | 4 Fluorite     | 5    Apatite
6 Feldspar | 7 Quartz    | 8 Topaz   | 9 Corundum | 10 Diamond

Mohs Scale Kit Wikipedia Wikipedia