Mohs Hardness Scale

Mohs hardness kit, containing one specimen of each mineral on the ten-point hardness scale

The Mohs scale of mineral hardness is an ordinal scale measuring the hardness of minerals through the abilities of harder materials able to scratch softer materials. Invented by German mineralogist Friedrich Mohs in 1812, it is one of various definitions of hardness in material science.

Mohs hardness	Mineral	Chemical formula	Absolute hardness	Image
1	Talc	Mg3Si4O10(OH)2	1
2	Gypsum	CaSO4·2H2O	3
3	Calcite	CaCO3	9
4	Fluorite	CaF2	21
5	Apatite	Ca5(PO4)3(OH−,Cl−,F−)	48
6	Orthoclase feldspar	KAlSi3O8	72
7	Quartz	SiO2	100
8	Topaz	Al2SiO4(OH−,F−)2	200
9	Corundum	Al2O3	400
10	Diamond	C	1500

Hardness	Substance or mineral
0.2–0.3	caesium, rubidium
0.5–0.6	lithium, sodium, potassium
1	talc
1.5	gallium, strontium, indium, tin, barium, thallium, lead, graphite, ice
2	hexagonal boron nitride, calcium, selenium, cadmium, sulfur, tellurium, bismuth, gypsum
2–2.5	halite (rock salt)
2.5–3	gold, silver, aluminium, zinc, lanthanum, cerium, Jet (lignite)
3	calcite, copper, arsenic, antimony, thorium, dentin
3.5	platinum
4	fluorite, iron, nickel
4–4.5	steel
5	apatite (tooth enamel), zirconium, palladium, obsidian (volcanic glass)
5.5	beryllium, molybdenum, hafnium, glass, cobalt
6	orthoclase, titanium, manganese, germanium, niobium, rhodium, uranium
6–7	fused quartz, iron pyrite, silicon, ruthenium, iridium, tantalum, opal, peridot, tanzanite, jade
7	osmium, quartz, rhenium, vanadium
7.5–8	emerald, hardened steel, tungsten, spinel
8	topaz, cubic zirconia
8.5	chrysoberyl, chromium, silicon nitride, tantalum carbide
9	corundum, tungsten carbide, titanium nitride
9–9.5	silicon carbide (carborundum), titanium carbide
9.5–10	boron, boron nitride, rhenium diboride (a-axis), stishovite, titanium diboride
10	diamond, carbonado
>11	nanocrystalline diamond (hyperdiamond, ultrahard fullerite), rhenium diboride (c-axis)

Comparison with Vickers scale

This is a comparison between Mohs's scale and the similar Vicker's scale.

Mineral name	Hardness (Mohs)	Hardness (Vickers) kg/mm2
Graphite	1–2	VHN10=7–11
Tin	1½	VHN10=7–9
Bismuth	2–2½	VHN100=16–18
Gold	2½	VHN10=30–34
Silver	2½	VHN100=61–65
Chalcocite	2½–3	VHN100=84–87
Copper	2½–3	VHN100=77–99
Galena	2½	VHN100=79–104
Sphalerite	3½–4	VHN100=208–224
Heazlewoodite	4	VHN100=230–254
Carrollite	4½–5½	VHN100=507–586
Goethite	5–5½	VHN100=667
Hematite	5–6	VHN100=1,000–1,100
Chromite	5½	VHN100=1,278–1,456
Anatase	5½–6	VHN100=616–698
Rutile	6–6½	VHN100=894–974
Pyrite	6–6½	VHN100=1,505–1,520
Bowieite	7	VHN100=858–1,288
Euclase	7½	VHN100=1,310
Chromium	8½	VHN100=1,875–2,000