MOHS HARDNESS SCALE
The Mohs Hardness Scale is used to gauge the relative hardness of any given mineral or gemstone material.
Below is the scale:
7. Quartz (Amethyst, Citrine)
9. Corundum (Ruby, Sapphire)
To test a gemstone for hardness, use one of the above materials to attempt to scratch the gemstone. If the gemstone is able to be scratched by the material, the stone’s hardness is less than the material.
For example, if you used a corundum to scratch a tanzanite, you’d find the corundum would cause scratches on the surface of the tanzanite. This is because corundum is a 9 on the hardness scale, and tanzanite is a 6-7. Conversely, tanzanite would be unable to scratch the corundum, as its hardness is much less.
Generally speaking, the hardest stones should be set in rings and bracelets, as they both can get much more wear than a necklace or earrings. If you want a fluorite ring, be sure it’s placed in a mount that provides protection to the stone, such as a bezel setting