Mohs scale of mineral hardness
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The Mohs scale of mineral hardness (or simply Mohs scale) is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material.
Contents
General
The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly. The samples of matter used by Mohs are all different minerals. Minerals are pure substances found in nature.
The Mohs scale is a purely ordinal scale. For example, corundum (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum.
Minerals
Classical scale
| Mohs hardness | Mineral | Chemical formula | Image |
|---|---|---|---|
| 1 | Talc | Mg3Si4O10(OH)2 | |
| 2 | Gypsum | CaSO4·2H2O | |
| 3 | Calcite | CaCO3 | |
| 4 | Fluorite | CaF2 | |
| 5 | Apatite | Ca5(PO4)3(OH−,Cl−,F−) | |
| 6 | Orthoclase feldspar | KAlSi3O8 | |
| 7 | Quartz | SiO2 | |
| 8 | Topaz | Al2SiO4(OH−,F−)2 | |
| 9 | Corundum | Al2O3 | |
| 10 | Diamond | C |
Intermediate scale
| 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[1] |
| 2 | hexagonal boron nitride,[2] 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),[3] stishovite, titanium diboride |
| 10 | diamond, carbonado |
| >11 | nanocrystalline diamond (hyperdiamond, ultrahard fullerite), rhenium diboride (c-axis)[3] |
References
- ↑ "Ice is a mineral" in Exploring Ice in the Solar System. messenger-education.org
- ↑ Berger, Lev I. (1996). Semiconductor Materials (First ed.). Boca Raton, FL: CRC Press. p. 126
- ↑ 3.0 3.1 Levine, Jonathan B.; Tolbert, Sarah H.; Kaner, Richard B. (2009). "Advancements in the Search for Superhard Ultra-Incompressible Metal Borides" (PDF). Advanced Functional Materials. pp. 3526–3527. doi:10.1002/adfm.200901257.
