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Information about Biotite

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Two fragments of Biotite
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A Biotite slice
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K(Mg, Fe)3AlSi3O10(F, OH)2. More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers include siderophyllite.

Biotite is a sheet silicate. Iron, magnesium, aluminum, silicon, oxygen, and hydrogen form sheets that are weakly bond together by potassium ions. It is sometimes called "iron mica" because it is more iron-rich than phlogopite. It is also sometimes called "black mica" as opposed to "white mica" (muscovite) -- both form in some rocks, in some instances side-by-side.

Like other mica minerals, biotite has a highly perfect basal cleavage, and consists of flexible sheets, or lamellae, which easily flake off. It has a monoclinic crystal system, with tabular to prismatic crystals with an obvious pinacoid termination. It has four prism faces and two pinacoid faces to form a pseudohexagonal crystal. Although not easily seen because of the cleavage and sheets, fracture is uneven. It has a hardness of 2.5 - 3, a specific gravity of 2.7 - 3.1, and an average density of 3.09 g/cm³. It is colored greenish to brown or black, and even yellow when weathered. It can be transparent to opaque, has a vitreous to pearly lustre, and a grey-white streak. In its weathered yellow, sparkly form, it is a common type of “fool’s Gold” (Pyrite is the official “fool’s Gold”). When biotite is found in large chunks, they are called “books” because it resembles a book with pages of many sheets.

Biotite is found in a wide variety of igneous rocks and metamorphic rocks. For instance, biotite occurs in the lava of Mount Vesuvius and at Monzoni. It is an essential phenocryst in some varieties of lamprophyre. Biotite is occasionally found in large sheets, especially in pegmatite veins, as in New England, Virginia and North Carolina. Other notable occurrences include Bancroft and Sudbury, Ontario. It is an essential constituent of many metamorphic schists, and it forms in suitable compositions over a wide range of pressure and temperature.

It is not industrially useful, but it is mined using quarrying and underground mining (depending on the depth of the biotite) for collection purposes.

Biotite is used extensively to constrain ages of rocks, by either potassium-argon dating or argon-argon dating. Because argon escapes readily from the biotite crystal structure at high temperatures, these methods may provide only minimum ages for many rocks. Biotite is also useful in assessing temperature histories of metamorphic rocks, because the partitioning of iron and magnesium between biotite and garnet is sensitive to temperature.

Biotite is used in electrical devices.

Biotite was named by J.F.L. Hausmann in 1847 in honour of the French physicist Jean-Baptiste Biot, who, in 1816, discovered optical properties of micas.

See also

References

"The Mineral Biotite". 1995,1996 Amethyst Gallery Inc. [1]

"Biotite Mineral Data". [2]

"Biotite". [3]

"BIOTITE". LoveToKnow 1911 Online Encyclopedia. 2003, 2004 LoveToKnow. [4]
A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties.
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Mica may refer to:
  • Mica, a silicate mineral group
  • The biblical prophet Micah
  • The book of Micah in the Tanakh
  • Mica is a song by Danish indie rock band Mew.

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Phlogopite is a yellow, greenish or reddish brown member of the mica family of phyllosilicates. It is also known as magnesium mica.

Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg 3AlSi3
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silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate ("fluorosilicate"), [SiF6]2−
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Muscovite (also known as Common mica, Isinglass, or Potash mica[3]) is a phyllosilicate mineral of aluminium and potassium with formula: KAl2(AlSi3O10)(F,OH)2.
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Mica may refer to:
  • Mica, a silicate mineral group
  • The biblical prophet Micah
  • The book of Micah in the Tanakh
  • Mica is a song by Danish indie rock band Mew.

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A lamella is a gill-shaped structure: fine sheets of material held adjacent one another, with fluid in-between-(or simply 'welded'-plates). They appear in biological and engineering contexts, such as filters and heat exchangers.
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monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a parallelogram as base.
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The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in
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Please assist in recruiting an expert or [ improve this article] yourself. See the talk page for details. This article has been tagged since November 2006.
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Green is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nm. It is considered one of the additive primary colors.
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Brown, when used as a general term, is a color which is a dark yellow, orange, or red, of low luminance relative to lighter or white colored objects.[1]

Some pale orange and yellow colors of lower saturation are called light browns.
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Black is the color of objects that do not reflect light in any part of the visible spectrum.

Scientifically, a black object absorbs all the colors of the visible spectrum and reflects none of them.
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Yellow is the color evoked by light that stimulates both the L and M (long- and medium-wavelength) cone cells of the retina about equally, but does not significantly stimulate the S
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pyrite, or iron pyrite, is iron sulfide, FeS2. It has isometric crystals that usually appear as cubes. The cube faces may be striated (parallel lines on crystal surface or cleavage face) as a result of alternation of the cube and pyritohedron faces.
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Igneous rocks (etymology from latin ignis, fire) are rocks formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.
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Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat (greater than 150 degrees Celsius) and extreme pressure causing profound
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Lava is molten rock expelled by a volcano during an eruption. When first expelled from a volcanic vent, it is a liquid at temperatures from 700 °C to 1,200 °C (1,300 °F to 2,200 °F).
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Mount Vesuvius (Italian: Monte Vesuvio, Latin: Mons Vesuvius) is a volcano east of Naples, Italy. It is the only volcano on the European mainland to have erupted within the last hundred years, although it is not currently erupting.
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phenocryst is a relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of a porphyritic igneous rock. Phenocrysts often have euhedral forms either due to early growth within a magma or by post-emplacement recrystallization.
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Lamprophyres (Greek Lampros, "bright", and the terminal part of the word "porphyry", meaning "rocks containing bright porphyritic crystals")

Lamprophyres are uncommon, small volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths,
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Pegmatite is a very coarse-grained igneous rock that has a grain size of 20 mm or more; such rocks are referred to as pegmatitic.

Most pegmatites are composed of quartz, feldspar and mica; in essence a "granite".
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New England

Political history
Chartering as Plymouth Council for New England 1620
Formation as United Colonies of New England 1643
Formation as Dominion of New England 1686
Admission to U.S.
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Commonwealth of Virginia

Flag of Virginia Seal
Nickname(s): Old Dominion, Mother of Presidents
Motto(s): Sic semper tyrannis

Official language(s) English

Capital Richmond
Largest city
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The State of North Carolina

Flag of North Carolina Seal
Nickname(s): Tar Heel State; Old North State;
The Rip Van Winkle State
''Motto(s): Esse quam videri (Latin: To be, rather than to seem)''

Official language(s)
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Town of Bancroft
Bancroft's centre.
Motto: A four seasons playground.
Bancroft's location in relation to Ontario.
Coordinates:
Country Canada
Province Ontario
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City of Greater Sudbury, Ontario
Ville de Grand-Sudbury, Ontario

Flag
Coat of arms
Nickname: The Nickel City
Motto: Aedificemus
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Ontario


Flag Coat of arms
Motto: Ut Incepit Fidelis Sic Permanet (Latin: Loyal she began, loyal she remains)

Capital Toronto
Largest city Toronto
Official languages English (de facto)
Government
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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.
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Potassium-argon or K-Ar dating is a geochronological method used in many geoscience disciplines. It is based on measuring the products of the radioactive decay of potassium (K), which is a common element found in materials such as micas, clay minerals, tephra and evaporites.
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