Olivine is the name of a group of rock-forming magnesium iron silicate that are typically found in mafic and ultramafic igneous rocks (such as basalt, gabbro, dunite, diabase, and peridotite) and marbles. It is not scientifically classified as an individual mineral species, but is rather recognized as a mineral group with the Forsterite and Fayalite end members. Pure Forsterite is uncommon, and pure Fayalite is very rare. It takes its name from its typically olive-green colour due to traces of nickel in the rock. It is a light near emerald green to the more common pale yellowish green; also found colorless, greenish brown to black in colour. The olivine consists of a silicon (Si) and oxygen (O) framework scattered among atoms of a metallic additive, usually magnesium (Mg) or iron (Fe) but sometimes calcium (Ca). Many people know olivine because it is a very popular green gemstone, peridot. Some ultramafic rocks can be composed of almost all olivine and these are called dunites or peridotites. Peridotites contain the same chemical makeup as the molten magma in the Earth’s mantle. It is one of the most common minerals in the earth. Olivine is also found in iron- nickel meteorites and other planets (the U. S. Geological Survey have shown that Olivine can also be found on Mars) and big grains have been reported in many of them. It is transparent to translucent with a glassy luster and a hardness between 6.5 and 7.0. It is the only common igneous mineral with these properties.
Olivine has a very high crystallization temperature compared to other minerals. That makes it one of the first minerals to crystallize from a magma. During the slow cooling of a magma, crystals of olivine may form and then settle to the bottom of the magma chamber because of their relatively high density. This concentrated accumulation of olivine can result in the formation of olivine-rich rocks such as dunite in the lower parts of a magma chamber. When olivine is metamorphosed, it is transformed into serpentine.
Olivine is very reactive to weathering. Bright green mineral loses its charm swiftly in the weathering environment. It becomes dull, earthy, and yellowish brown. This material is usually a mixture of clay minerals and iron hydroxide goethite and it is known as iddingsite. It also shows very little resistance to hydrothermal metamorphism. Hot and chemically aggressive fluids quickly alter olivine-rich igneous rocks into metamorphic rock known as serpentinite. It is also an important constituent of many stony and mixed meteorites.
The Olivine Pools in Hawaiian Islands are naturally-formed swimming pools located on a lava shelf which stretches along the coastline. When the sea is calm, the area is excellent for both swimming and sunbathing.
APPLICATIONS OF OLIVINE
Slag conditioning in steel Industry
Foundry sand in steel Industry
Refractories and refractory sand in steel Industry
Tap hole filler for electrical arc furnaces
High pressure water jet cutting
Roofing tiles to reduce ultraviolet (UV) light-induced deterioration
Ballast in oil production platforms in the North Sea.
Fertilizer/soil conditioner to increase Mg and Fe as nutrients in soil.
As a raw material in Production of magnesium metal
Absorbing the CO2 from atmosphere (being tested at the moment)