Mohs scale of mineral hardness 1

Mohs scale of mineral hardnessThe Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of aharder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogistFriedrich Mohs and is one of several definitions of hardness in materials science.[1] The method of comparinghardness by seeing which minerals can scratch others, however, is of great antiquity, having first been mentioned byTheophrastus in his treatise On Stones, circa 300 BC, followed by Pliny the Elder in his Naturalis Historia, circa 77AD.[2] [3] [4]

MineralsThe Mohs scale of mineral hardness is based on the ability of one natural sample of matter to scratch another. Thesamples of matter used by Mohs are all minerals. Minerals are pure substances found in nature. Rocks are made upof one or more minerals.[5] As the hardest known naturally occurring substance when the scale was designed,diamonds are at the top of the scale. The hardness of a material is measured against the scale by finding the hardestmaterial that the given material can scratch, and/or the softest material that can scratch the given material. Forexample, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fallbetween 4 and 5.[6]

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. The table below shows comparison with absolute hardness measured by asclerometer, with pictorial examples.[7] [8]

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–)2200

Mohs scale of mineral hardness 2

9 Corundum Al2O3 400

10 Diamond C 1600

On the Mohs scale, graphite (a principal constituent of pencil "lead") has a hardness of 1.5; a fingernail, 2.2–2.5; acopper penny, 3.2–3.5; a pocketknife 5.1; a knife blade, 5.5; window glass plate, 5.5; and a steel file, 6.5.[9] A streakplate (unglazed porcelain) has a hardness of 7.0. Using these ordinary materials of known hardness can be a simpleway to approximate the position of a mineral on the scale.[1]

Intermediate hardnessThe table below incorporates additional substances that may fall between levels:

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

2 hexagonal boron nitride,[10] calcium, selenium, cadmium, sulfur, tellurium, bismuth

2.5 to 3 magnesium, gold, silver, aluminium, zinc, lanthanum, cerium, Jet_(lignite) (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 (volcanic glass)

5.5 beryllium, molybdenum, hafnium

6 orthoclase, titanium, manganese, germanium, niobium, rhodium, uranium

6 to 7 glass, fused quartz, iron pyrite, silicon, ruthenium, iridium, tantalum, opal

7 quartz, vanadium, osmium, rhenium

7.5 to 8 hardened steel, tungsten, emerald, spinel

8 topaz, cubic zirconia

8.5 chrysoberyl, chromium, silicon nitride

9-9.5 corundum, silicon carbide (carborundum), tungsten carbide, titanium carbide, stishovite

9.5–10 rhenium diboride, tantalum carbide, titanium diboride, boron nitride, boron [11] [12] [13] [14] .

10 diamond

>10 nanocrystalline diamond (hyperdiamond, ultrahard fullerite)

Mohs scale of mineral hardness 3

Hardness (Vickers)Comparison between Hardness (Mohs) and Hardness (Vickers):[15]

Mineralname

Hardness (Mohs) Hardness (Vickers)kg/mm2

Graphite 1 - 2 VHN10=7 - 11

Tin 1½ - 2 VHN10=7 - 9

Bismuth 2 - 2½ VHN100=16 - 18

Gold 2½ - 3 VHN10=30 - 34

Silver 2½ - 3 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 9 VHN100=1,875 - 2,000

References[1] Encyclopædia Britannica. 2009. Encyclopædia Britannica Online. 22 Feb. 2009 "Mohs hardness." (http:/ / www. britannica. com/ EBchecked/

topic/ 387714/ Mohs-hardness)[2] Theophrastus on Stones (http:/ / www. farlang. com/ gemstones/ theophrastus-on-stones/ page_148/ view?searchterm=scratch)[3] Pliny the Elder.Naturalis Historia.Book 37.Chap. 15. ADamas: six varieties of it. Two remedies. (http:/ / www. perseus. tufts. edu/ cgi-bin/

ptext?lookup=Plin. + Nat. + 37. 15)[4] Pliny the Elder.Naturalis Historia.Book 37.Chap. 76. The methods of testing precious stones. (http:/ / www. perseus. tufts. edu/ cgi-bin/

ptext?lookup=Plin. + Nat. + 37. 76)[5] Learn science, Intermediate p. 42[6] American Federation of Mineralogical Societies. "Mohs Scale of Mineral Hardness" (http:/ / www. amfed. org/ t_mohs. htm)[7] Amethyst Galleries' Mineral Gallery What is important about hardness? (http:/ / www. galleries. com/ minerals/ hardness. htm)[8] Inland Lapidary Mineral Hardness and Hardness Scales (http:/ / www. inlandlapidary. com/ user_area/ hardness. asp)[9] William S. Cordua (1998). "The Hardness of Minerals and Rocks" (http:/ / www. gemcutters. org/ LDA/ hardness. htm). Lapidary Digest. .

Retrieved 2007-08-19. Hosted at International Lapidary Association (http:/ / www. gemcutters. org/ )[10] L. I. berger "semiconductor materials" CRC press, 1996 ISBN 0849389127, p. 126[11] Weintraub E. (1911). "On the properties and preparation of the element boron.". J. Ind. Eng. Chem. 3 (5): 299–301.

doi:10.1021/ie50029a007.[12] Solozhenko, V. L.; Kurakevych O. O.; Oganov A. R. (2008). "On the hardness of a new boron phase, orthorhombic γ-B28". Journal of

Superhard Materials 30 (6): 428–429. doi:10.3103/s1063457608060117.. Open access: (http:/ / mysbfiles. stonybrook. edu/ ~aoganov/ files/JSM-2008-6b-e. pdf)

Mohs scale of mineral hardness 4

[13] Zarechnaya, E. Yu.; Dubrovinsky, L.; Dubrovinskaia, N.; Filinchuk, Y.; Chernyshov, D.; Dmitriev, V.; Miyajima, N.; El Goresy, A. et al.(2009). "Superhard semiconducting optically transparent high pressure phase of boron". Phys. Rev. Lett. 102 (18): 185501.Bibcode 2009PhRvL.102r5501Z. doi:10.1103/physrevlett.102.185501. PMID 19518885.

[14] Oganov A.R., Solozhenko V.L. (2009). "Boron: a hunt for superhard polymorphs". Journal of Superhard Materials 31: 285-291.. Openaccess: (http:/ / mysbfiles. stonybrook. edu/ ~aoganov/ files/ Boron-history-JSM. pdf)

[15] "[[Mindat.org (http:/ / www. mindat. org/ min-1911. html)]"]. .

• Mohs hardness of elements is taken from G.V. Samsonov (Ed.) in Handbook of the physicochemical properties ofthe elements, IFI-Plenum, New York, USA, 1968.

• Cordua, William S. "The Hardness of Minerals and Rocks" (http:/ / www. gemcutters. org/ LDA/ hardness. htm).Lapidary Digest, c. 1990.

Article Sources and Contributors 5

Article Sources and ContributorsMohs scale of mineral hardness  Source: http://en.wikipedia.org/w/index.php?oldid=444930318  Contributors: 198.144.199.xxx, 345Kai, Adamv88, Afluegel, Alansohn, Albedo, Amorphagate,Anaxial, Arakunem, Archaeodontosaurus, Astynax, Atif.t2, Atreklin, Austin thomas bailey, Azure777, BartlebytheScrivener, BillFlis, Bjankuloski06en, Blerk, Blessing-light, Bobet, Bobo192,Bogey97, Brentt, BrianKnez, Bryan Derksen, C hill, CIreland, Can't sleep, clown will eat me, Catgut, Chamal N, Charles Matthews, Chetvorno, Chris.urs-o, ChrisCork, ChrisHodgesUK,Closedmouth, Cmglee, Coasterlover1994, Coelacan, Cole Petersburg, Conversion script, Cryptoid, Cutler, Cyclebeargc, DARTH SIDIOUS 2, Daarznieks, Dale Gerdemann, DanMS, DanielCD,Dblecros, Dept of Alchemy, Dkasak, Doctorwho123456, Donarreiskoffer, Dwayne, Eastlaw, Ed g2s, Elassint, Electron9, Elryacko, Epbr123, Farosdaughter, Fru1tbat, Fyrael, Gabbe, Gentgeen,Giftlite, Goderator, Gurch, Gökhan, H-b-g, Hakan Kayı, Harbuz, Helikophis, Hemmer, HereToHelp, Heron, Hut 8.5, Hylobates, Hyperdeath, I dream of horses, Iamsopro, Im.a.lumberjack,Interrobang², Ioannes Pragensis, Iridescent, Isis, Ivan Bajlo, Iwoelbern, JNW, JSpung, Jak123, Jauerback, Jesseboy889, Jjdon, John, KBi, Kanags, Karl-Henner, Kbh3rd, Keilana, Kencf0618,Kilo-rock, King of Hearts, Kitch, Kittil hagen, Knarf-bz, Knife Knut, Krellis, Kristof vt, LazyLaidBackEditor, LeaveSleaves, LeilaniLad, Liamgreyfrancis, Lilac Soul, Liso, Looxix, Luebuwei,Mandarax, Materialscientist, Mav, Mazca, Methecooldude, Mike1942f, Mikenorton, Mrs. High, Ms2150, Muriel Gottrop, Mygerardromance, Nadyes, Nemu, Nightscream, No more D, Noctibus,Nortonius, Officially Mr X, Orlady, Oxymoron83, Paleorthid, Patrick, Pb30, Persian Poet Gal, Peter Horn, Peter bertok, Peterlewis, PeyoteFlyer, Pharos, Pil56, Private Pilot, Promethean, Pwjb,Quantpole, Rachel Wa L., Reyk, Rissebigfoot, Rjwilmsi, Rrostrom, Sakimori, Sanao, Scetoaux, Schmloof, Sean.hoyland, ShelfSkewed, Shimgray, Siamodiversi, SidP, Slicksub, Snowolf, Soap,Stan Shebs, Storm Rider, Tak015, Tanaats, TerraFrost, Tetracube, Thatguy123456789, The Anome, The Master of Mayhem, Thingg, Tom harrison, Trapolator, TreasureBug, Triwbe, Tumble,Twinsday, Unyoyega, Uruiamme, VederJuda, Vorophobe, Vsmith, Vuong Ngan Ha, Wikifuzzygum, Wikipelli, Wolfmankurd, XJamRastafire, Yekrats, Yurei-eggtart, Yurik, ZPM, Zamphuor,482 anonymous edits

Image Sources, Licenses and ContributorsImage:Talc block.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Talc_block.jpg  License: Public Domain  Contributors: EugeneZelenko, Sanao, Saperaud, Wela49Image:Gypse Arignac.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gypse_Arignac.jpg  License: Creative Commons Attribution-Sharealike 3.0,2.5,2.0,1.0  Contributors: DidierDescouensImage:Calcite-sample2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Calcite-sample2.jpg  License: Creative Commons Attribution 2.0  Contributors: Jarno from Rotterdam,NetherlandsImage:Fluorite with Iron Pyrite.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Fluorite_with_Iron_Pyrite.jpg  License: Creative Commons Attribution 2.5  Contributors: Originaluploader was H at en.wikipediaImage:Apatite crystals.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Apatite_crystals.jpg  License: Public Domain  Contributors: OG59, Rocket000, Überraschungsbilder, 1anonymous editsImage:OrthoclaseBresil.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:OrthoclaseBresil.jpg  License: Creative Commons Attribution-Sharealike 3.0,2.5,2.0,1.0  Contributors:Didier DescouensImage:Quartz Brésil.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Quartz_Brésil.jpg  License: Creative Commons Attribution 3.0  Contributors: Didier DescouensImage:Topaz cut.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Topaz_cut.jpg  License: GNU Free Documentation License  Contributors: w:de:Benutzer:Wela49Wela49Image:Cut Ruby.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cut_Ruby.jpg  License: Public Domain  Contributors: User:BkellImage:Rough diamond.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Rough_diamond.jpg  License: Public Domain  Contributors: Unknown USGS employee

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