Minerals

Minerals are classified by key chemical constituents; the two dominant systems are the Dana classification and the Strunz classification. Silicate minerals comprise approximately 90% of the Earth's crust. Other important mineral groups include the native elements (made up of a single pure element) and compounds (combinations of multiple elements) namely sulfides (e.g. Galena PbS), oxides (e.g. quartz SiO₂), halides (e.g. rock salt NaCl), carbonates (e.g. calcite CaCO₃), sulfates (e.g. gypsum CaSO₄·2H₂O), silicates (e.g. orthoclase KAlSi₃O₈), molybdates (e.g. wulfenite PbMoO₄) and phosphates (e.g. pyromorphite Pb₅(PO₄)₃Cl).