Dolomite. Magnesium calcium carbonate, MgCa(CO3)2.
Enstatite. See [Pyroxenes].
Epidote. Calcium aluminium iron silicate, Ca2(AlOH)(Al,Fe‴)2(SiO4)3.
Felspars. A series of silicates of aluminium with potassium or sodium or calcium, or all of these. Orthoclase, KAlSi3O8, and the corresponding sodium form, Albite, NaAlSi3O8, lie at one end of the series, and the calcium felspar Anorthite, CaAl2(SiO4)2, at the other. While Orthoclase crystallises in the monoclinic system, a triclinic form, Microcline, with the same composition, is also common. All the other felspars are triclinic, and, with microcline, are often styled plagioclases. The principal felspars between Albite and Anorthite are Oligoclase, the "soda-lime felspar," and Labradorite, the "lime-soda felspar."
Flint. See [Chalcedony].
Garnets. A series of silicates with the general composition of R3″R2‴(SiO3)4, R″ being Ca, Fe″, or Mn, and R‴ being Al or Fe‴. The common red garnet in mica-schists is Almandine, Fe3Al2(SiO3)4, while that in altered limestones is Grossularite, Ca3Al2(SiO3)4.
Glauconite. A hydrous iron potassium silicate, with some aluminium, magnesium, and calcium, formed in marine deposits.
Gypsum. Hydrous calcium sulphate, CaSO4 + 2 H2O.
Hornblende. See [Amphiboles].
Hypersthene. See [Pyroxenes].