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Metamorphic rocks Reference Libraries

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Biotite
2005-05-26 12:03:39

Biotite is a common phyllosilicate mineral that contains potassium, magnesium, iron and aluminium. It is sometimes called "iron mica" and is found in granitic rocks, gneisses, and schists. Like other mica minerals, biotite has a highly perfect basal cleavage, its flexible sheets easily flaking off. It has a hardness of 2.5 - 3, a specific gravity of 2.7 - 3.1, is colored greenish to brown or...

Chromite Iron Chromium Oxide
2005-05-26 11:26:59

Chromite, iron magnesium chromium oxide: (Fe,Mg)Cr2O4, is an oxide mineral belonging to the spinel group. Magnesium is always present in variable amounts, also aluminium and iron substitute for chromium. Chromite is found in peridotite and other layered ultramafic intrusive rocks and also found in metamorphic rocks such as serpentinites. Ore deposites of chromite form as early magmatic...

Conglomerate geology
2005-05-26 11:13:08

In geology, a conglomerate is a rock consisting of other stones that have been cemented together. Conglomerates are sedimentary rocks consisting of subangular clasts and are thus differentiated from breccias, which consist of angular clasts. Both conglomerates and breccias are characterized by clasts larger than sand (>2 mm). There are two varieties of conglomerate, defined by texture:...

Garnierite
2005-05-26 10:59:02

Garnierite is a mineral composed of hydrous nickel silicates a member of the serpentine group with formula: (Ni,Mg)3Si2O5(OH). Népouite is a synonym. Garnierite is important as a source of nickel and is mined from laterite deposits which are formed by intense weathering and secondary enrichment of ultramafic igneous rocks.

Gneiss
2005-05-26 10:50:45

Gneiss is a common and widely distributed type of rock formed by high grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. Gneissic rocks are coarsely laminated and largely recrystallized but do not carry large quantities of micas, chlorite or other platy minerals. Gneisses that are metamorphosed igneous rocks or their...

Kyanite
2005-05-26 09:41:33

The mineral kyanite is an aluminium silicate of the sillimanite group (along with andalusite and sillimanite), also called alumino-silicate. It has the formula Al2O3·SiO2 (Al2SiO5). Its hardness varies widely depending on its crystallographic direction, from 5 to 7.5, and it has a specific gravity of 3.56-3.67. It is translucent, usually blue, but possibly white, gray, green, or black. It...

Marble
2005-05-26 08:52:39

Marble is metamorphosed limestone, composed of fairly pure calcite (a crystalline form of calcium carbonate, CaCO3). It is extensively used for sculpture, as a building material, and in many other applications. Faux marble or faux marbling is a wall painting technique that imitates the color patterns of real marble (not to be confused with paper marbling). Marble dust can be combined with...

Muscovite
2005-05-26 08:35:42

Muscovite, also known as potash mica, is a phyllosilicate mineral of aluminium and potassium. It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets), which are often highly elastic. Muscovite has a hardness of 2 - 2.25 and a specific gravity of 2.76 - 3. It can be colorless or tinted through grays, browns, greens, yellows, or rarely violet or red, and can be...

Peridotite
2005-05-25 19:19:16

Peridotite is a dense, coarse grained ultrabasic rock, consisting mainly of the minerals olivine and pyroxene. Peridotite is also a group of mantle derived igneous rocks. They all are ultramafic or ultrabasic meaning they contain less than 45% silica and are high in iron and magnesium. Members of the peridotite family include: Dunite - predominately composed of olivine, with minor...

Phyllite
2005-05-25 19:13:32

Phyllite is a type of metamorphic rock primarily composed of quartz, sericite mica, and chlorite; the rock is intermediate in grade between slate and mica schist. Minute crystals of graphite, sericite, or chlorite impart a silky sheen to the surfaces of cleavage (or schistosity).

Word of the Day
grass-comber
  • A landsman who is making his first voyage at sea; a novice who enters naval service from rural life.
According to the OED, a grass-comber is also 'a sailor's term for one who has been a farm-labourer.'