Tungsten, Cobalt, and More on Mohs Scale of Mineral Hardness

A mineral is traditionally defined as a compound that is solid, and which is found primarily in nature. While there are a number of ways in which minerals can be studied, their degree of hardness being one of them. The Mohs scale of mineral hardness is a chart that categorizes minerals according to their scratch resistance, as well their ability to scratch other materials. As suggested by the name, the Mohs scale of mineral hardness was developed by a German geologist by the name of Friedrich Mohs. Though initially developed in 1812, the Mohs scale of hardness is still widely used today by students, teachers, and professionals in the field of geology.

General Hardness Resources

Mohs Hardness

Mineral

Chemical Formula

Absolute Hardness

1

Talc

Mg3Si4O10(OH)2

1

2

Gypsum

CaSO4 x2h20

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

1600

Hardness

Substance or Mineral

0.2-0.3

caesium, rubidium

0.5-0.6

lithium, sodium, potassium

1

talc

1.5

gallium, strontium, indium, lin, barium, thallium, lead, graphite

2

hexagonal boron, nitride, calcium, selenium, cadmium, sulfur, tellurium, bismuth

2.5-3

magnesium, gold, silver, aluminum, zinc, lanthanum, cerium, Jet_(lignite)

3

calcite, copper, arsenic, antimony, thorium, dentin

4

fluorite, iron, nickel

4 to 4.5

platinum, steel

5

apatite, cobalt, zirconium, palladium, tooth enamel, obsidian

5.5

beryllium, molybdenum, hafnium

6

orthoclase, titanium, manganese, germanium, nioblum, rhodium, uranium

6 to 7

glass, fused quartz, iron pyrite, silicon, ruthenium, iridium, tantalum, opal

7

quartz, canadium, osmium, rhenium

7.5 to 8

hardened steel, tungsten, emerald, spinel

8

topaz, cubic zirconia

8.5

chysoberyl, chromium, silicon nitride

9-9.5

corundum, silicon carbide )carborundum), tungsten carbide, titanium carbide, stishovite

9.5-10

rhenium dibordie, tantalum carbide, titanium dibordie, boron nitride, boron

10

Diamond

>10

nanocrystalline diamond (hyperdiamond, ultrahard fullerite)

Miscellaneous Mineral and Gemstone Resources

Content written and provided by Vanessa LeBeau