In 1812, Friedich Mohs created a scale based on how one natural mineral can scratch another. Number one is the softest with number 10 being the hardest. The scale is very useful when considering whether to mount a particular stone in a ring, which gets a lot of wear and has potential to be knocked about or whether to mount it in a brooch, which would get very little wear.

Moh`s Scale of Hardness

 

1     Talc            Can be easily scratched with a fingernail
2     Gypsum       Can be scratched with a fingernail
3     Calcite        Can be scratched with a coin
4     Flourite       Can be scratched with a knife but they won`t scratch glass
5     Apatite        Can be scratched with a knife and they can just scratch glass
6     Feldspar       A steel file witll scratch these minerals and they in turn will easily scratch window glass
7     Quartz         These minerals scratch metal, glass and softer stones very easily.
8     Topaz          Will scratch quartz and softer stones
9     Corundum    Will scratch quartz and softer stones
10   Diamond       Will scratch corundum (sapphire and ruby)