olivinegroep

The olivine group is a collection of silicate minerals characterized by their green color and granular appearance. These minerals are members of the nesosilicate class, meaning their silicate tetrahedra are arranged as isolated units. The general chemical formula for the olivine group is (Mg, Fe)2SiO4, where magnesium and iron are the primary cations. The relative proportions of magnesium and iron determine the specific mineral within the group. Forsterite, the magnesium-rich endmember, has the formula Mg2SiO4, while fayalite, the iron-rich endmember, is Fe2SiO4. Minerals with intermediate compositions between forsterite and fayalite are known as olivine.

Olivine group minerals are significant components of the Earth's upper mantle, making them among the most abundant minerals in the planet. They are also found in mafic and ultramafic igneous rocks, such as basalt, gabbro, and peridotite, which are formed from cooled magma. Due to their relatively low melting points compared to other mantle minerals, they are often the first to melt when the mantle is heated. In addition to terrestrial occurrences, olivine has also been identified in meteorites and extraterrestrial dust. The gem variety of forsterite is known as peridot.