Reference work entry
The chemical composition of olivine is (Mg,Fe) 2[SiO 4]. Olivine is a magnesium iron silicate, and it gets its name from its olive-green colour. Its crystals are plank-like and are usually in granular aggregates. It has a vitreous lustre with a Mohs hardness of 6.6–7, a specific gravity of 3.2–3.5 and conchoidal fractures. This mineral mainly forms in ultramafic and mafic igneous rocks. It transforms to serpentine easily through alteration and is also a major component of meteorites. Gem-quality olivine is usually found in coarse peridot in the upper mantle. Predominant mining countries include Egypt, Myanmar, the United States and China (Fig. 3).
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