What is peridotite composed of?
peridotite, a coarse-grained, dark-coloured, heavy, intrusive igneous rock that contains at least 10 percent olivine, other iron- and magnesia-rich minerals (generally pyroxenes), and not more than 10 percent feldspar.
Which igneous rock is made of 100 olivine?
troctolite, coarse-grained, intrusive igneous rock that is composed almost entirely of olivine (often iron-rich) and plagioclase feldspar (labradorite or bytownite).
What mafic rock is composed of 100 olivine?
Ultramafic refers to the extremely mafic rocks composed of mostly olivine and some pyroxene which have even more magnesium and iron and even less silica. These rocks are rare on the surface, but make up peridotite, the rock of the upper mantle.
Which region of the Earth is composed of olivine peridotite?
Earth’s mantle is thought to be composed mainly of peridotite. Some of the occurrences of peridotite on Earth’s surface are thought to be rocks from the mantle that have been brought up from depth by deep-source magmas. Ophiolites and pipes are two structures that have brought mantle peridotite to the surface.
How is peridotite made?
Peridotite is derived from Earth’s mantle, either as solid blocks and fragments, or as crystals accumulated from magmas that formed in the mantle. The compositions of peridotites from these layered igneous complexes vary widely, reflecting the relative proportions of pyroxenes, chromite, plagioclase, and amphibole.
What is the difference between peridotite and olivine?
Peridotite contains at least 40 percent olivine and some pyroxene. Unlike the olivine grains, the pyroxene grains in peridotite have a visible cleavage when viewed under a hand lens. Peridotite forms much of Earth’s mantle and can occur as nodules that are brought up from the mantle by kimberlite or basalt magmas.
What rocks contain olivine?
Olivine Occurrence Most olivine found at Earth’s floor is in dark-colored igneous rocks. It usually crystallizes inside the presence of plagioclase and pyroxene to form gabbro or basalt.
How is peridotite rock formed?
Is peridotite mafic?
Peridotite is a very dense, coarse-grained, olivine-rich, ultra- mafic intrusive rock. It is noted for its low silica content, and contains very little or no feldspar ( orthoclase, plagioclase).
Where is olivine found?
Olivine has been found in stony and stony-iron meteorites that orbit near Mars and Jupiter. Olivine is also found in distinct form on the parts of a planet or asteroid near the mantle-core boundary.
What is characteristics of peridotite?
Peridotite is a very dense, coarse-grained, olivine-rich, ultra- mafic intrusive rock. It is noted for its low silica content, and contains very little or no feldspar ( orthoclase, plagioclase). It is a common component of oceanic lithosphere, and is derived from the upper mantle.
What are olivine crystals?
An olivine crystal is normally a roundish lump 2 mm or less across. A mass of pure olivine crystals thus forms a distinctive granular texture. Olivine’s color ranges from the deep green of peridot to the olive green of olives to the pale olive green of pale green olives.
What is an peridotite rock?
Peridotite is the general name for the ultrabasic or ultramafic intrusive rocks, dark green to black in color, dense and coarse-grained texture, often as layered igneous complex.
What is olivine crystal?
Olivine is typically olive green in color, but can also be yellow-green to bright green and brownish-green to brown. The opacity of olivine ranges from transparent to translucent, and its texture is brittle with many fractures. Olivine is commonly associated with the green gemstone peridot.
What rock contains olivine?
Olivine is most commonly found in igneous rocks of low silica content, such as basalts and gabbros, and is occasionally found in metamorphic rocks.
What is olivine composed of?
The mineral olivine (/ˈɒl. ɪˌviːn/) is a magnesium iron silicate with the chemical formula (Mg2+, Fe2+) 2SiO 4. It is a type of nesosilicate or orthosilicate. The primary component of the Earth’s upper mantle, it is a common mineral in Earth’s subsurface, but weathers quickly on the surface.
Is olivine rare?
It is usually easily identifiable because of its bright green color and glassy luster. Olivine sand grains from Hawaii. Olivine is actually very rare in sand because it is highly susceptible to weathering.
How do you identify peridotite?
Classic peridotite is bright green with some specks of black, although most hand samples tend to be darker green. Peridotitic outcrops typically range from earthy bright yellow to dark green; this is because olivine is easily weathered to iddingsite.
Is olivine a precious stone?
Olivine is used as the gemstone for August and are most valued in its bright lime green and dark olive tints. Olivine as a gemstone is mostly mined at the San Carlos Reservation in Arizona to create small olivine gemstones infused with chromite or other minerals.
Is peridot and peridotite the same?
The word peridotite comes from the gemstone peridot, which consists of pale green olivine. Classic peridotite is bright green with some specks of black, although most hand samples tend to be darker green.
What is the silica content of peridotite?
Peridotite is a generic name used for coarse-grained, dark-colored, ultramafic igneous rocks. Peridotites usually contain olivine as their primary mineral, frequently with other mafic minerals such as pyroxenes and amphiboles. Their silica content is low compared to other igneous rocks,…
Is peridotite a coarse-grained igneous rock?
A coarse-grained ultramafic igneous rock. Peridotite is a dense, coarse-grained igneous rock consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica (SiO4−. 4). It is high in magnesium (Mg2+), reflecting the high proportions of magnesium-rich olivine, with appreciable iron.
What is another name for peridotite?
Certain volcanic rocks, sometimes called komatiites, are so rich in olivine and pyroxene that they also can be termed peridotite. Small pieces of peridotite have even been found in lunar breccias.
How can you tell the difference between peridotite and olivine?
Unlike the olivine grains, the pyroxene grains in peridotite have a visible cleavage when viewed under a hand lens. Peridotite forms much of Earth’s mantle and can occur as nodules that are brought up from the mantle by kimberlite or basalt magmas.