Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich end-member of the olivine solid solution series. It is isomorphous with the iron-rich end-member, fayalite. Forsterite crystallizes in the orthorhombic system (space group Pbnm) with cell parameters a 4.75 Å (0.475 nm), b 10.20 Å (1.020 nm) and c 5.98 Å (0.598 nm).
Forsterite (big tabular and colorless) on sanidine (little colorless crystals) with hematite (reddish)
Orange forsterite with a portion of tephroite
Forsterite var. peridot with minor pyroxene (brown) on vesicular basalt. Collected near Peridot, Arizona.
The mineral olivine is a magnesium iron silicate with the chemical formula (Mg,Fe)2SiO4. It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickly on the surface. For this reason, olivine has been proposed as a good candidate for accelerated weathering to sequester carbon dioxide from the Earth's oceans and atmosphere, as part of climate change mitigation. Olivine also has many other historical uses, such as the gemstone peridot, as well as industrial applications like metalworking processes.
Olivine
Olivine in cross-polarized light
Olivine grains that eroded from lava on Papakolea Beach, Hawaii
Light green olivine crystals in peridotite xenoliths in basalt from Arizona