| Class | Defining Anions | Example |
|---|---|---|
| Native elements | None: no charged ions | Copper metal (Cu) |
| Oxides | Oxygen ion (O2−) | Hematite (Fe2O3) |
| Halides | Chloride (Cl−), fluoride (F−), | Halite (NaCl) |
| bromide (Br−), iodide (I−) | ||
| Carbonates | Carbonate ion (CO32−) | Calcite (CaCO3) |
| Sulfates | Sulfate ion (SO42−) | Anhydrite (CaSO4) |
| Silicates | Silicate ion (SiO44−) | Olivine (Mg,Fe)2SiO4 |
| Sulfides | Sulfide ion (S2−) | Pyrite (FeS2) |