Olivine is a simple orthosilicate in which the SiO 4 tetrahedra are independent of each other. It is a solid solution of the end-members forsterite (Mg 2SiO 4) and fayalite (Fe 2SiO 4), although most examples are closer to the forsterite end-member.

Olivine is very susceptible to alteration and often has a brownish weathering rind of assorted clay minerals.

Olivine is most commonly found in igneous rocks of low silica content, such as basalts and gabbros, and is occasionally found in metamorphic rocks.

Chemical composition - (Mg, Fe) 2SiO 4
Hardness - 6.5-7
Specific gravity - 3.2-4.4
Transparency - Transparent to translucent
Colour - Yellowish green to green, also colourless, greenish brown to black
Streak - White
Lustre - Vitreous
Cleavage/fracture - Imperfect / conchoidal
Crystal habit/mode of occurrence - Prismatic (equant to elongate) / granular, massive