An unusual quartz-bearing orthopyroxene-rich websterite xenolith has been found in an alkali basaltic tuff at Szigliget, BakonyBalaton Highland Volcanic Field (BBHVF), western Hungary.
What is olivine websterite?
outcrop, olivine websterite is a dark grey, medium to coarsely crystalline rock. Petrographic study reveals presence of olivine, clinopyroxene, orthopyroxene and phlogopite as essential phases with plagioclase and chromite as accessories.
What two minerals compose the mineral websterite?
A pyroxenite (ultramafic rock) with >5% clinopyroxene and >5% orthopyroxene. It usually consists of roughly equal proportions of orthopyroxene and clinopyroxene.
Where is pyroxenite found?
Distribution. They frequently occur in the form of dikes or segregations in gabbro and peridotite: in Shetland, Cortland on the Hudson River, North Carolina (websterite), Baltimore, New Zealand, and in Saxony. They are also found in the Bushveld Igneous Complex in South Africa and The Great Dyke in Zimbabwe.
What type of rock is Websterite?
ultramafic igneous rock Websterite is ultramafic igneous rock that consists of roughly equal proportions of orthopyroxene and clinopyroxene. It is a type of pyroxenite. Websterite is named after the town Webster in North Carolina.
How deep is Dunite formed?
about 400 km Dunite and other peridotite rocks are considered the major constituents of the Earth’s mantle above a depth of about 400 km (250 mi).
What is Orthopyroxene made of?
In Earth’s crust, pyroxenes are found in a wide range of igneous and metamorphic rocks. They are most abundant in the dark-colored igneous rocks, such as basalt and gabbro, that comprise most of the oceanic crust. …
|Physical Properties of Pyroxenes|
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Where is kimberlite rock found?
Generally speaking, kimberlites are found only in cratons, the oldest surviving areas of continental crust, which form the nuclei of continental landmasses and have remained virtually unchanged since their formation eons ago.
What is the origin of gabbro?
Gabbro (/b. ro/) is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth’s surface. … Gabbro is also found as plutons associated with continental volcanism.
What type of stone is granite?
intrusive igneous rock granite, coarse- or medium-grained intrusive igneous rock that is rich in quartz and feldspar; it is the most common plutonic rock of the Earth’s crust, forming by the cooling of magma (silicate melt) at depth.
What color is silicate?
The silicate minerals containing iron and magnesium are generally dark-colored (dark green, gray, or black) and are referred to as mafic (or ferromagnesian) minerals. Plagioclase feldspars may range from pale-colored sodium-rich varieties (such as albite), to darker grey, calcium-rich varieties (such as labradorite).
How are komatiites formed?
Komatiites are considered to have been formed by high degrees of partial melting, usually greater than 50%, and hence have high MgO with low K2O and other incompatible elements.
What kind of rock is a pyroxenite?
Pyroxenites are ultramafic intrusive igneous rocks composed almost entirely of dark Pyroxene group minerals rich in iron and magnesium, e.g., Augite, Diopside, Hypersthene, Diallage, Bronzite, and Enstatite, unlike other mafic minerals Olivine and Amphibole.
What is pyroxenite used for?
Pyroxenite is used as a flux in sintering and also in iron and steel industry. The magnesium silicates do not call for calcination (unlike the carbonates) and thus lowers energy requirement in the blast furnace.
Is pyroxenite magnetic?
Due to these inclusions of magnetite, Bronzite-Pyroxenite is magnetic and Golden Amphibolite is not.
Where do you find peridotite?
Peridotite is the dominant rock of the upper part of Earth’s mantle. The compositions of peridotite nodules found in certain basalts and diamond pipes (kimberlites) are of special interest, because they provide samples of Earth’s mantle brought up from depths ranging from about 30 km to 200 km or more.
How is syenite formed?
Syenites are products of alkaline igneous activity, generally formed in thick continental crustal areas, or in Cordilleran subduction zones. To produce a syenite, it is necessary to melt a granitic or igneous protolith to a fairly low degree of partial melting.
Is Augite a mineral?
Augite is a common rock-forming pyroxene mineral with formula (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6. The crystals are monoclinic and prismatic.
What mineral is in dunite?
olivine Dunite, light yellowish green, intrusive igneous ultramafic rock that is composed almost entirely of olivine.
Is dunite a volcanic rock?
Dunite (otherwise called olivinite, not to be mistaken for the mineral olivenite) is a volcanic, plutonic shake, of ultramafic arrangement, with coarse-grained or phaneritic surface.
Does Obsidian exist?
obsidian, igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Obsidian is extremely rich in silica (about 65 to 80 percent), is low in water, and has a chemical composition similar to rhyolite.
What color is Orthopyroxene?
pale green The keys to identifying orthopyroxene are its relief, usually pale green (sometimes pleochroic to pink) color, low-order interference colors, and near 90o cleavage seen in some views. Color – Commonly light green, but some orthopyroxene shows marked pleochroism to pink. Relief is moderate to fairly high.
Where does Orthopyroxene occur?
Orthopyroxenes typically occur as fibrous or lamellar (thin-plated) green masses in igneous and metamorphic rocks and in meteorites. All except the theoretical end-member ferrosilite occur naturally.
What is the difference between orthopyroxene and clinopyroxene?
In orthopyroxenes the M2 site is usually octahedral and commonly contains Fe and Mg. In clinopyroxenes, larger cations (such as Li and Na) are in eightfold coordination in the M2 site (the larger cations need a different geometry to accommodate them, which reduces the symmetry to monoclinic).
How much is kimberlite worth?
RAPAPORT… DiamondCorp recorded a sale of kimberlite diamonds from its Lace mine in South Africa for the first time since 1931, achieving an average price of $175 per carat.
How do I identify a kimberlite rock?
kimberlite, also called blue ground, a dark-coloured, heavy, often altered and brecciated (fragmented), intrusive igneous rock that contains diamonds in its rock matrix. It has a porphyritic texture, with large, often rounded crystals (phenocrysts) surrounded by a fine-grained matrix (groundmass).
Can you find diamond in quartz?
Diamonds can scratch every other mineral, but only diamonds can scratch diamonds. Quartz, the most likely mineral to be mistaken for diamonds in uncut rough form, ranks 7 on the Mohs Hardness Scale.
Where is gabbro found in the world?
mid-ocean ridges Gabbro is a dense, mafic intrusive rock. It generally occurs as batholiths and laccoliths and is often found along mid-ocean ridges or in ancient mountains composed of compressed and uplifted oceanic crust.
What is gabbro used for in everyday life?
The most common use of gabbro is as a crushed stone or aggregate. Crushed gabbro is used as a base material in construction projects, as a crushed stone for road construction, as railroad ballast, and anywhere that a durable crushed stone is needed as fill.
What types of rock is gabbro?
1 Mafic Intrusive Igneous Rocks. Gabbro is a mafic intrusive coarse-grained rock with allotriomorphic texture. Gabbros contain low silicon (no Quartz or Alkali feldspar) and essentially of ferromagnesian minerals and Plagioclase feldspar rich in calcium.