The Chemical Classification of Gems & Minerals
From The Gemology Project
Contents
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) |