The Chemical Classification of Gems & Minerals

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The Chemical Classification of Gems & Minerals

Gems can be organized into classes, based on their chemistry.

Class Description
Class I: Pure Elements Metals, alloys, semi-metals and non-metals
Class II: Sulfides Sulfur is the principal anion: includes tellurides and arenides
Class III: Halides Halogen elements are anions: F, Cl, Br
Class IV: Oxides Oxygen is the principal anion, includes hydroxides in which the hydroxyl radical (OH) acts as the anion
Class V a:Carbonates Carbonate radical (CO3) is the principal anion
Class V b:Borates Borate radical (BO3) and boate groups are anions
Class VI a:Tungstates Anions are principally WO4
Class VI b:Sulphates sulphate radical (SO4) is the principal anion
Class VII: Phosphates Anions are principally PO4
Class VIII: Silicates Silicate groups as anions combining with other elements: includes silica SiO2

Class I Pure Elements

Class I Pure Elements
Diamond Carbon (C)

Class II Sulfides

Class II Sulfides
Marcasite FeS2
Pyrite FeS2
Sphalerite ZnS

Class III Halides

Class III Halides
Fluorite CaF2

Class IV Oxides

Class IV Oxides
Anatase TiO2
Brookite TiO2
Chrysoberyl BeAl2O4
Corundum Al2O3
Hematite Fe2O3
Opal SiO2nH2O
Quartz SiO2
Rutile TiO2
Spinel MgAl2O4

Class Va Carbonates

Class Va Carbonates
Aragonite CaCO3
Azurite Cu3(OH/CO3)2
Calcite CaCO3
Cerrussite PbCO3
Malachite Cu2(OH)2CO3
Rhodochrosite MnCO3
Smithsonite ZnCO3

Class Vb Borates

Class Vb Borates
Hambergite Be2(OH/BO3)
Sinhalite MgAl(BO4)
Ulexite NaCaB5O9.8H2O

Class VIa Tungstates

Class VIa Tungstates
Scheelite Ca(WO4)

Class VIb Sulphates

Class VIb Sulphates
Barite Ba(SO4)

Class VII Phosphates

Class VII Phosphates
Amblygonite LiAl(F,OH/PO4)
Apatite Ca5(F/PO4)2
Brazilianite NaAl3(OH2/PO4)2
Turquoise CuAl6((OH2)PO4)44H20

Class VIII Silicates

Class VIII Silicates
Andalusite Al2SiO5
Beryl Be3Al2 (SiO3)6
Iolite (Cordierite) Mg2Al4Si5O18
Garnet X3Y2Si3O12 (X = Mg, Fe or Ca) (Y = Al else Fe3+ or Cr)
Jadeite NaAlSi2O6
Nephrite Ca2(MgFe)5(Si4O11)2
Topaz Al2SiO4(FOH)2
Tourmaline (Na1+, Ca2+)(Li1+, Mg2+, Al3+). (Al3+, Fe3+, Mn3+)6(BO3)3 (Si6O18) (OH)4
Peridot Mg2SiO4, Fe2SiO4
Zircon Zr(SiO4)