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) |
