MOHS Scale of Hardness

Mohs Scale of Hardness

Hardness Substance
2.5 Amber, Ivory, Shell
3-4 Pearl
5 Glass
5.5-5 Lapis, Lazuli
5-6 Opal, Turquoise
6-6.5 Sodalite
6-7 Onyx, Peridot, Quartz
7 Agate, Amethyst, Citrine, Prasiolite
7-7.5 Garnet, Tourmaline
7.5 Zircone
7.5-8 Aquamarine, Emerald
8 Topaz
8.5 Alexandrite
9 Ruby, Sapphire
10 Diamond
A hardness of 1 or 2 can be scratched with a fingernail, 3 to 4 scratched with a penny, 5-6 scratched with a knife blade, 6 scratched with a stepl file, 7 to 10 can scratch glass.