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Schist 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...

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...

Schist
2005-05-25 18:35:54

The schists form a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is produced. By definition, schist contains more than 50% platy and elongated minerals, often finely...

Slate
2005-05-25 17:09:09

Slate is a fine-grained, homogeneous, sedimentary rock composed of clay or volcanic ash which has been metamorphosed (foliated) in layers (bedded deposits). Slate can be made into roofing shingles ('roofing slates' in the United Kingdom), because it has two lines of breakability: cleavage and grain. This makes it possible to split slate into thin sheets. Slate is mainly composed of quartz...

Tourmaline
2005-05-25 11:15:23

The mineral tourmaline is chemically one of the most complicated silicate minerals. It is a complex silicate of aluminium and boron but because of isomorphous replacement (solid solution) its composition varies widely with iron, magnesium and lithium and other elements entering into the combination to a greater or lesser extent. Tourmaline belongs to the trigonal crystal system and occurs as...

Word of the Day
call-note
  • The call or cry of a bird or other animal to its mate or its young.
'Call-note' is newer than 'bird-call,' which originally referred to 'an instrument for imitating the note of birds' but now also refers to 'the song or cry of a bird.'
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