Gemstones are graded by hardness, this helps jewellers choose appropriate minerals and gems based on the wear and tear they might encounter.
The Mohs scales uses 10 minerals as its reference, these are:
Generally jewellery appropriate gemstones fall in the 7-10 range with some exceptions being Amber, Pearl, Opal, and Coral (Organic Gem Materials)
The Mohs scale measures a minerals resistance to scratches (hardness) using a reference mineral. Developed in 1812 by German mineralogist, Friedrich Mohs. The scale uses a NON-linear numbering system from 1 (softest) to 10 (hardest)
The scientific definition of hardness is the ability to resist scratching. Hardness depends on the bonds that hold the atoms together within a crystal structure. If a material is harder it will disrupt those bonds leading to what we would call a ‘scratch’.
Using this chart for reference jewellers can get a rough idea of how delicate a material is.