Mohs hardness scale and observations on hardness of some additional materials

mineral Mohs hardness other materials observations on the minerals

talc 1 very easily scratched by the fingernail; has a greasy feel

gypsum 2 ~2.2 fingernail can be scratched by the fingernail

calcite 3 ~3.2 copper penny very easily scratched with a knife and just scratched with a copper coin

fluorite 4 very easily scratched with a knife but not as easily as calcite

apatite 5 ~5.1 pocketknife scratched with a knife with difficulty

~5.5 glass plate

orthoclase 6 ~6.5 steel needle cannot be scratched with a knife, but scratches glass with difficulty

quartz 7 ~7.0 streak plate scratches glass easily

topaz 8 scratches glass very easily

corundum 9 cuts glass

diamond 10 used as a glass cutter

Source: Modified from C. Klein, Minerals and Rocks: Exercises in Crystallography, Mineralogy, and Hand Specimen Petrology. Copyright 1989 John Wiley & Sons. Reprinted by permission of John Wiley & Sons, Inc.