Identification and Occurrence
- Olivine is named for its typically olive-green color, thought to be a result of traces of nickel.
- Translucent olivine is sometimes used as a gemstone called peridot.
- Olivine occurs in both mafic and ultramafic igneous rocks and as a primary mineral in certain metamorphic rocks.
- Mg-rich olivine crystallizes from magma that is rich in magnesium and low in silica.
- Ultramafic rocks usually contain substantial olivine, and those with an olivine content of over 40% are described as peridotites.
- Mg-rich olivine has been discovered in meteorites, on the Moon, and Mars.
- Olivine has been found falling into infant stars and on asteroid 25143 Itokawa.
- Spectral signatures of olivine have been seen in the dust disks around young stars.
- Olivine has been detected in the tails of comets and in samples from a comet collected by the Stardust spacecraft.
- Magnesium-rich olivine has been detected in the planetesimal belt around the star Beta Pictoris.
- Minerals in the olivine group crystallize in the orthorhombic system.
- The structure can be described as a hexagonal, close-packed array of oxygen ions.
- There are three distinct oxygen sites, two distinct metal sites, and only one distinct silicon site.
- The crystal structure of olivine is characterized by isolated silicate tetrahedra.
- Olivine has a Pbnm space group and exists in mirror planes and an inversion center.
- At high temperatures and pressures, olivine undergoes phase transformations.
- The high-pressure polymorphs of olivine include wadsleyite and ringwoodite.
- These high-pressure polymorphs have different crystal structures and properties compared to olivine.
- The presence of water can affect the stability and phase transformations of olivine.
- Understanding the behavior of olivine under high pressures is important for studying Earth's mantle and geodynamic processes.
Industrial and Historical Uses
- Olivine has industrial applications in metalworking processes.
- It has been used as a refractory material in high-temperature applications.
- Olivine has historical uses as a gemstone, particularly as peridot or chrysolite.
- The finest gem-quality olivine has been obtained from Zabargad Island in the Red Sea.
- Olivine's unique properties and abundance make it a versatile and valuable mineral in various industries.
Olivine Weathering and Uses
- Olivine undergoes phase transitions at certain depths within the Earth's mantle.
- These phase transitions affect the density of the mantle and mantle convection.
- The pressure at which these phase transitions occur depends on temperature and iron content.
- Olivine is unstable on the Earth's surface and easily alters into iddingsite in the presence of water.
- The presence of iddingsite on Mars suggests the existence of liquid water in the past.
- Olivine can be used to sequester carbon dioxide (CO2) through enhanced weathering.
- Crushed olivine weathers completely within a few years, sequestering CO2 from the atmosphere.
- Olivine is used as a substitute for dolomite in steel works.
- The aluminium foundry industry uses olivine sand for casting objects in aluminium.
- Olivine is marketed as an ideal rock for sauna stoves in Finland due to its high density and resistance to weathering.
Olivine Data Sources