iPedia Free Information Center

Information about Augite

Augite

General
CategorySilicate mineral
Chemical formula(Ca,Mg,Fe)SiO3
Identification
ColorPale brown to purplish or greenish brown
Crystal systemMonoclinic
Cleavage{110} good
Fractureuneven
Mohs Scale hardness5 to 6.5
LusterVitreous
Refractive indexα = 1.671 - 1.735,
β = 1.672 - 1.741,
γ = 1.703 - 1.774
Specific gravity3.19 - 3.56


Augite is a mineral described chemically as (Ca,Mg,Fe)SiO3 or calcium magnesium iron silicate. The crystals are monoclinic and prismatic. Augite has two prominent prismatic cleavages, meeting at angles near 90°.

Augite is a solid solution in the pyroxene group. Diopside and hedenbergite are important endmembers in augite, but augite can also contain significant aluminium, titanium, and sodium and other elements. The calcium content of augite is limited by a miscibility gap between it and pigeonite and orthopyroxene: when occurring with either of these other pyroxenes, the calcium content of augite is a function of temperature and pressure, but mostly of temperature, and so can be useful in reconstructing temperature histories of rocks. With declining temperature, augite may exsolve lamellae of pigeonite and/or orthopyroxene. There is also a miscibility gap between augite and omphacite, but this gap occurs at lower temperature and is not well understood.

It is found in igneous rocks such as gabbro and basalt. It also occurs in relatively high-temperature metamorphic rocks such as mafic granulite.

Occasional specimens have a shiny appearance that give rise to the mineral's name, which is from the Greek augites, meaning "brightness", although ordinary specimens have a dull (dark green, brown or black) finish.

References

  • Deer, W. A., Howie, R. A., and Zussman, J. (1992). An introduction to the rock-forming minerals (2nd ed.). Harlow: Longman ISBN 0-582-30094-0
The silicate minerals make up the largest and most important class of rock-forming minerals. They are classified based on the structure of their silicate ion group.

Subclasses:

Nesosilicates or Isosilicates

Nesosilicates (or orthosilicates
..... Click the link for more information.
A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs.
..... Click the link for more information.
A crystal system is a category of space groups, which characterize symmetry of structures in three dimensions with translational symmetry in three directions, having a discrete class of point groups.
..... Click the link for more information.
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.
..... Click the link for more information.
Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types:
  • Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes.

..... Click the link for more information.
fracture is the (local) separation of a body into two, or more, pieces under the action of stress.

The word fracture is often applied to bones of living creatures, or to crystals or crystalline materials, such as gemstones or metal.
..... Click the link for more information.
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
..... Click the link for more information.
For other senses of this word, see lustre.


Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock, or mineral.
..... Click the link for more information.
The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical glass has a refractive index of 1.
..... Click the link for more information.
This article requires authentication or verification by an expert.
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.
..... Click the link for more information.
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.
..... Click the link for more information.
Calcium (IPA: /ˈkalsiəm/) is the chemical element in the periodic table that has the symbol Ca and atomic number 20. It has an atomic mass of 40.078.
..... Click the link for more information.
Magnesium has the symbol Mg, the atomic number 12, and an atomic mass of 24.31. Magnesium is the ninth most abundant element in the universe by mass. It constitutes about 2% of the Earth's crust by mass, and it is the third most abundant element dissolved in seawater.
..... Click the link for more information.
3, 4, 6
(amphoteric oxide)
Electronegativity 1.83 (Pauling scale)
Ionization energies
(more) 1st: 762.5 kJmol−1
2nd: 1561.9 kJmol−1
3rd: 2957 kJmol−1

Atomic radius 140 pm
Atomic radius (calc.
..... Click the link for more information.
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−
..... Click the link for more information.
CRYSTAL is a quantum chemistry ab initio program, designed primarily for calculations on crystals (3 dimensions), slabs (2 dimensions) and polymers (1 dimension) using translational symmetry, but it can be used for single molecules.[1] It is written by V.R. Saunders, R.
..... Click the link for more information.
A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single
..... Click the link for more information.
The pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rocks. They share a common structure comprised of single chains of silica tetrahedra and they crystalise in the monoclinic and orthorhombic system.
..... Click the link for more information.
Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms complete solid solution series with hedenbergite (FeCaSi2O6) and augite, and partial solid solutions with orthopyroxene and pigeonite.
..... Click the link for more information.
Hedenbergite, calcium iron pyroxene CaFeSi2O6, is a black mineral closely allied to diopside and, owing to the isomorphous replacement of iron by magnesium, there is no sharp line of division between them.

References


..... Click the link for more information.
Aluminium (IPA: /ˌæljʊˈmɪniəm/, /ˌæljəˈmɪniəm/) or aluminum (IPA: /əˈluːmɪnəm/
..... Click the link for more information.
Titanium (IPA: /tʌɪˈteɪniəm/) is a chemical element; in the periodic table it has the symbol Ti and atomic number 22.
..... Click the link for more information.
Sodium (IPA: /ˈsəʊdiəm/) is a chemical element which has the symbol Na (Latin: natrium), atomic number 11, atomic mass 22.9898 g/mol, common oxidation number +1.
..... Click the link for more information.
Pigeonite is a mineral in the clinopyroxene group. It has a general formula of (Ca,Mg,Fe)(Mg,Fe)Si2O6 The calcium cation fraction can vary from 5% to 25%, with iron and magnesium making up the rest of the cations.
..... Click the link for more information.
The pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rocks. They share a common structure comprised of single chains of silica tetrahedra and they crystalise in the monoclinic and orthorhombic system.
..... Click the link for more information.
Omphacite is a member of the pyroxene group of silicate minerals with formula: (Ca,Na)(Mg,Fe2+,Al)Si2O6. It is a variably deep to pale green or nearly colorless variety of pyroxene.
..... Click the link for more information.
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.
..... Click the link for more information.
Gabbro (IPA: /ˈgabrəʊ/) is a dark, coarse-grained, intrusive igneous rock chemically equivalent to basalt.
..... Click the link for more information.
Basalt (IPA: /ˈbæsɒlt, bəˈsɒlt/) is a common gray to black extrusive volcanic rock. It is usually fine-grained due to rapid cooling of lava on the Earth's surface.
..... Click the link for more information.
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
..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
Herod_Archelaus


page counter