Friedrich Moh's Scale of Scratch Hardness


This hardness measure, while useful for field identification, is only indicative of relative hardness. The difference in hardness between numbers on the scale are not equivalent. A good example is that the difference between harnesses 7 and 8 is much smaller than the difference between 9 and 10.

Moh's Scale of Hardness
Hardness Minerals/GemstonesTest
1 Talc, SulpherScratched w/fingernail
2 Gypsum, Amber (2-3)Scratched w/fingernail
3 Calcite, Coral (3-4), Pearl (3-4), Malachite (3.5-4)Scratched w/copper penny
4 Fluorite, RhodochrositeScratched w/ knife blade easily
5 Apatite, Lapis (5-6), Turquoise (5-6), Opal (5.5-6)Scratched w/knife blade
6 Feldspars, Moonstone, Tanzanite (6.5-7), Peridot (6.5-7)Scratched w/steel file
7 Quartz, Tourmaline (7-7.5), Garnet (7-7.5), Beryl (7.5-8) Scratches glass
8 Topaz, Alexandrite (8-8.5)Scratches glass
9 CorundumScratches glass
10 DiamondScratches glass



*This table assembled from various mineral and gemstone guides.




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