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Olivine grains that eroded from lava on Papakolea BeachHawaii Light green olivine crystals in peridotite xenoliths in basalt from Arizona Olivine basalt from the Moon, collected by the crew of Apollo 15 Olivine is named for its typically olive-green color thought to be a result of traces of nickelthough it may alter to a reddish color from the oxidation of iron.
It is also called chrysolite or chrysolithe, from the Greek words for gold and stone. Some of the finest gem-quality olivine has been obtained from a body of mantle rocks on Zabargad Island in the Red Sea.
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.
That magma crystallizes to mafic rocks such as gabbro and basalt. Ultramafic rocks such as peridotite and dunite can be residues left after extraction of magmas, and typically they are more enriched in olivine after extraction of partial melts.
The metamorphism of impure dolomite or other sedimentary rocks with high magnesium and low silica content also produces Mg-rich olivine, or forsterite. Fe-rich olivine is relatively much less common, but it occurs in igneous rocks in small amounts in rare granites and rhyolitesand extremely Fe-rich olivine can exist stably with quartz and tridymite.
In contrast, Mg-rich olivine does not occur stably with silica minerals, as it would react with them to form orthopyroxene Mg,Fe 2Si2O6. Experiments have documented that olivine at high pressures e. The spectral signature of olivine has been seen in the dust disks around young stars.
The tails of comets which formed from the dust disk around the young Sun often have the spectral signature of olivine, and the presence of olivine was verified in samples of a comet from the Stardust spacecraft in The atomic scale structure of olivine looking along the a axis.
A projection of the unit cell is shown by the black rectangle. Minerals in the olivine group crystallize in the orthorhombic system space group Pbnm with isolated silicate tetrahedra, meaning that olivine is a nesosilicate.
In an alternative view, the atomic structure can be described as a hexagonal, close-packed array of oxygen ions with half of the octahedral sites occupied with magnesium or iron ions and one-eighth of the tetrahedral sites occupied by silicon ions.
There are three distinct oxygen sites marked O1, O2 and O3 in figure 1two distinct metal sites M1 and M2 and only one distinct silicon site. O1, O2, M2 and Si all lie on mirror planeswhile M1 exists on an inversion center. O3 lies in a general position.
High pressure polymorphs[ edit ] At the high temperatures and pressures found at depth within the Earth the olivine structure is no longer stable. These phase transitions lead to a discontinuous increase in the density of the Earth's mantle that can be observed by seismic methods. They are also thought to influence the dynamics of mantle convection in that the exothermic transitions reinforce flow across the phase boundary, whereas the endothermic reaction hampers it.
Increasing the iron content decreases the pressure of the phase transition and narrows the wadsleyite stability field. Increasing the temperature increases the pressure of these phase transitions. Weathering[ edit ] Olivine altered to iddingsite within a mantle xenolith.
Olivine is one of the weaker common minerals on the surface according to the Goldich dissolution series. It alters into iddingsite a combination of clay minerals, iron oxides and ferrihydrites readily in the presence of water.
There is also olivine in Eid municipality. At Svarthammaren in Norddal olivine was mined from around towith a daily output up to metric tons.Get study help fast! Search through millions of guided step-by-step solutions or ask for help from our community of subject experts 24/7.
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The mineral olivine (/ ˈ ɒ l ɪ ˌ v iː n /) is a magnesium iron silicate with the formula (Mg 2+, Fe 2+) 2 Si O 4.
Thus it is a type of nesosilicate or orthosilicate. It is a common mineral in Earth's subsurface but weathers quickly on the surface. Home; About Us; Mineral Identification.
InfoBank, KnowledgeBank's field data catalog, is a structured information storage scheme of databases and software that provide organized access to USGS Coastal and Marine data and metadata.