ElementChromium
SymbolCr
Atomic Mass51.9961
Atomic Number24
Name OriginsGreek, chroma = color
Year Discovered1780
Discovered CreditsN. L. Vanquelin at Paris, France
RemarksHard, blue-white metal. Soluble in HCl and H2SO4 but not HNO3, H3PO4 or HClO4 due to formation of protective layer. Resists oxidation in air. Main use in alloys, chrome plating, and metal ceramics.
Diagnostic TestsChromium gives a borax bead test in the reducing flame a color which is yellow to red (hot) and yellowish green (cold). Under the reducing flame the bead color is a fine emerald green, hot and cold. Chromium gives a Na2(NH4)(PO4) bead a dirty green color (hot) and a fine green color (cold). In solution, the addition of NH4OH produces a green precipitate of Cr(OH)3. Note: chromium's name is in reference to the various colors a solution will have depending on the oxidation state Cr2+ (yellow), Cr3+ (green), or Cr6+ (orange).
ReferencesEmsley, J., 1991; THE ELEMENTS : Sec. Ed., Clarendon Press, Oxford, 251 p.

Naturally Ocurring Isotopes :

Mass Nuclide Number Natural Abundance Half-life Half-life Unit Decay Mode Decay Mode MeV Decay Mode %
49.946046 50 4.35 % Stable
51.940509 52 83.79 % Stable
52.940651 53 9.5 % Stable
53.938882 54 2.36 % Stable

82 Minerals sorted by % of Cr (Chromium) :

Chromium100.00 %Cr
Ferchromide87.47 %Cr3Fe1-x(x=0,6)
Tongbaite86.66 %Cr3C2
Carlsbergite78.78 %CrN
Eskolaite68.42 %Cr2O3
Isovite67.41 %(Cr,Fe)23C6
Guyanaite61.17 %CrO(OH)
Bracewellite61.17 %Cr+++O(OH)
Grimaldiite61.17 %Cr+++O(OH)
Brezinaite54.88 %Cr3S4
Magnesiochromite54.08 %MgCr2O4
Chromite46.46 %Fe++Cr2O4
Zincochromite44.56 %ZnCr2O4
Manganochromite43.80 %(Mn,Fe++)(Cr,V)2O4
Rilandite41.15 %(Cr,Al)6SiO11·5(H2O) (?)
Caswellsilverite37.38 %NaCrS2
Schollhornite36.87 %Na0.3CrS2·(H2O)
Daubreelite36.10 %Fe++Cr2S4
Lopezite35.35 %K2Cr2O7
Mcconnellite35.24 %CuCrO2
Cochromite35.00 %(Co,Ni,Fe++)(Cr,Al)2O4
Kalininite34.94 %ZnCr2S4
Chromatite33.32 %CaCrO4
IMA1999-01832.46 %Ca0.2(H2O)2CrS2
Nichromite30.65 %(Ni,Co,Fe++)(Cr,Fe+++,Al)2O4
Yimengite29.19 %K(Cr,Ti,Fe,Mg)12O19
Tarapacaite26.78 %K2CrO4
Donathite23.65 %(Fe++,Mg)(Cr,Fe+++)2O4
Florensovite23.59 %Cu(Cr1.5Sb0.5)S4
Knorringite22.95 %Mg3Cr2(SiO4)3
Kosmochlor22.89 %NaCr+++Si2O6
Chromdravite20.99 %NaMg3(Cr,Fe+++)6(BO3)3Si6O18(OH)4
Uvarovite20.78 %Ca3Cr2(SiO4)3
Hawthorneite19.99 %Ba[Ti3Cr4Fe4Mg]O19
Olkhonskite19.94 %(Cr+++,V+++)2Ti3O9
Mathiasite18.54 %(K,Ca,Sr)(Ti,Cr,Fe,Mg)21O38
Lindsleyite17.69 %(Ba,Sr)(Ti,Cr,Fe,Mg)21O38
Crocoite16.09 %PbCrO4
Stichtite15.90 %Mg6Cr2(CO3)(OH)16·4(H2O)
Barbertonite15.90 %Mg6Cr2(CO3)(OH)16·4(H2O)
Hashemite15.70 %Ba(Cr,S)O4
Petterdite15.29 %PbCr+++2(CO3)2(OH)4·H2O
Krinovite14.14 %NaMg2CrSi3O10
Shuiskite13.34 %Ca2(Mg,Al)(Cr,Al)2(SiO4)(Si2O7)(OH)2·(H2O)
Volkonskoite13.12 %Ca0.3(Cr+++,Mg,Fe+++)2(Si,Al)4O10(OH)2·4(H2O)
Redledgeite12.96 %BaTi6Cr+++2O16·(H2O)
Carmichaelite12.91 %(Ti,Cr,Fe)[O2-x(OH)x],x~0.5
Chromceladonite12.33 %KCrMg(Si4O10)(OH)2
Vuorelainenite11.73 %(Mn++,Fe++)(V+++,Cr+++)2O4
Chromferide11.04 %Fe3Cr1-x (x=0,6)
Iranite10.22 %Pb10Cu(CrO4)6(SiO4)2(F,OH)2
Hemihedrite10.21 %Pb10Zn(CrO4)6(SiO4)2F2
Dietzeite9.52 %Ca2(IO3)2(CrO4)
Phoenicochroite9.52 %Pb2(CrO4)O
Wattersite9.47 %Hg+4Hg++Cr++++++O6
Woodallite9.46 %Mg6Cr2(OH)16Cl2·4H2O
Chromphyllite9.38 %(K,Ba)(Cr,Al)2[AlSi3O10](OH,F)2
Redingtonite8.49 %(Fe++,Mg,Ni)(Cr,Al)2(SO4)4·22(H2O)
Vauquelinite7.37 %Pb2Cu(CrO4)(PO4)(OH)
Embreyite7.05 %Pb5(CrO4)2(PO4)2·(H2O)
Fornacite6.93 %Pb2Cu(CrO4)(AsO4)(OH)
Cassedanneite6.86 %Pb5(VO4)2(CrO4)2·(H2O)
Loveringite6.81 %(Ca,Ce)(Ti,Fe+++,Cr,Mg)21O38
Edoylerite6.65 %Hg++3Cr++++++O4S2
Dukeite6.40 %Bi+++24Cr++++++8O57(OH)6(H2O)3
Georgeericksenite6.12 %Na6CaMg(IO3)6(CrO4)2·12(H2O)
Bentorite6.03 %Ca6(Cr,Al)2(SO4)3(OH)12·26(H2O)
Natalyite5.74 %Na(V+++,Cr+++)Si2O6
Macquartite5.30 %Pb3Cu(CrO4)(SiO3)(OH)4·2(H2O)
Mongshanite5.24 %(Mg,Cr,Fe++)2(Ti,Zr)5O12
Polyakovite-(Ce)4.97 %(REE,Ca)4(Mg,Fe++)(Cr,Fe+++)2(Ti,Nb)2Si4O22
Deanesmithite4.34 %Hg+2Hg++3Cr++++++O5S2
Zhanghengite4.28 %(Cu,Zn,Fe,Al,Cr)
Iquiqueite3.55 %K3Na4Mg(Cr++++++O4)B24O39(OH)·12(H2O)
Heideite3.55 %(Fe,Cr)1+x(Ti,Fe)2S4
Mountkeithite3.34 %(Mg,Ni)11(Fe+++,Cr)3(SO4,CO3)3.5(OH)24·11(H2O)
Yedlinite3.17 %Pb6CrCl6(O,OH)8
Santanaite2.01 %9PbO·2PbO2·CrO3
Chrombismite1.36 %Bi16CrO27
Molybdofornacite1.32 %Pb2Cu[(As,P)O4][(Mo,Cr)O4](OH)
Ankangite1.29 %Ba(Ti,V+++,Cr+++)8O16
Khristovite-(Ce)0.85 %(Ca,REE)(Ce,REE)(Mg,Fe,Cr,Ti,V,Al)Mn++Al(SiO4)(Si2O7)(OH)(F,O)