Olivine

Olivine is a group of magnesium- and iron-rich silicate minerals whose structures contain isolated silica tetrahedra. Its principal members form a continuous solid-solution series between forsterite and fayalite.

Forsterite: Forsterite is the magnesium-rich end member of the olivine mineral series, with composition Mg₂SiO₄. It defines the magnesium-rich end of olivine’s principal solid-solution series.
Magnesium–iron substitution in olivine: Magnesium–iron substitution is the replacement of Mg²⁺ by Fe²⁺ in olivine’s crystal structure. This exchange produces the continuous compositional range between forsterite and fayalite.
Peridot: Peridot is the gem variety of olivine, typically colored green by iron. Transparent olivine crystals are cut and valued as peridot.
Dunite: Dunite is an ultramafic igneous rock composed predominantly of olivine. It represents rocks in which olivine is abundant enough to dominate the mineral assemblage.
Fayalite: Fayalite is the iron-rich end member of the olivine mineral series, with composition Fe₂SiO₄. It defines the iron-rich end of olivine’s principal solid-solution series.
Crystal defect: A crystal defect is a departure from the regular arrangement of atoms in a crystalline solid. Defects enable diffusion and deformation in olivine under geological conditions.
Mantle xenolith: A mantle xenolith is a fragment of Earth’s mantle carried to the surface by magma. Olivine in these fragments reveals the composition and history of the upper mantle.
Peridotite: Peridotite is a coarse-grained ultramafic rock composed chiefly of olivine and pyroxenes. It is the principal rock type of Earth’s upper mantle, where olivine is a major mineral.
Silicate mineral: A silicate mineral is a mineral whose structure contains silicon–oxygen units. Olivine belongs to this broad mineral family, but has an unusually isolated tetrahedral structure.
Olivine diffusion: Olivine diffusion is the temperature-dependent movement of atoms through olivine crystals. Diffusion can modify olivine compositions and preserve records of changing conditions.

Linked from 29 pages