The pyroxene silicate minerals enstatite (MgSiO₃) and ferrosilite (FeSiO₃) form a complete solid solution series and are common rock-forming minerals found in igneous and metamorphic rocks and meteorites. The intermediate composition, (Mg,Fe)SiO₃, is sometimes known as hypersthene although this name has been formally abandoned and replaced by enstatite or ferrosilite. Weathered enstatite with a small amount of iron takes on a submetallic luster and a bronze-like color. This material is termed bronzite although it is more correctly called altered enstatite. Most natural crystals are orthorhombic (space group Pbca) although three polymorphs are known. The high temperature, low pressure polymorphs are protoenstatite and proroferrosilite (also orthorhombic, space group Pbcn) while the low temperature forms, clinoenstatite and clinoferrosilite, are monoclinic (space group P2₁/c). This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... Rose des Sables (Sand Rose), formed of gypsum crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... In crystallography, the orthorhombic crystal system is one of the 7 lattice point groups. ... In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. ... 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. ... For fractures in bones, see Fracture (bone). ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... Figure 1:Mantle-peridotite xenolith with green peridot olivine and black pyroxene crystals from San Carlos Indian Reservation, Gila Co. ... The silicate minerals make up the the largest and most important class of rock-forming minerals. ... This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... 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 (from the Greek words meta, change, and morphe, form). The protolith is subjected to extreme heat (greater than 150 degrees Celsius) and pressure causing... A meteorite is a small extraterrestrial body that impacts the Earths surface. ... Hypersthene is a common rock-forming mineral belonging to the group of orthorhombic pyroxenes. ... Weathering is the process of decomposition and/or disintegration of rocks, soils and their minerals through natural, chemical, and biological processes that is, in place. ... For the file system called Lustre, see Lustre (file system) Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... Bronzite is a member of the pyroxene group of minerals, belonging with enstatite and hypersthene to the orthorhombic series of the group. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... In crystallography, the orthorhombic crystal system is one of the 7 lattice point groups. ... A space group is a mathematical symmetry group or symmetry group type of n-dimensional structures with translational symmetry in n independent directions, such as, for n = 3, a crystal. ... In general, a polymorph is something that can exist in several states or forms. ... In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. ...

Bronzite and hypersthene were known long before enstatite, which was first described by G. A. Kenngott in 1855.

An emerald green variety of enstatite is called chrome-enstatite and is cut as a gemstone. The green color is caused by traces of chromium, hence the varietal name. In addition, bronzite is also sometimes used as a gemstone. A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. ... General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6, 4, d Appearance silvery metallic Atomic mass 51. ...

Identification

Enstatite and the other orthorhombic pyroxenes are distinguished from those of the monoclinic series by their optical characteristics, such as straight extinction, much weaker double refraction and stronger pleochroism. They also have a prismatic cleavage that is perfect in two directions at nearly 90 degrees. Enstatite is white, gray, greenish or brown in color; its hardness is 5 - 6, and its specific gravity is 3.2 - 3.3. A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the division of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... Pleochroism is an optical phenomenon where due to double refraction of light by a colored gem or crystal, the light is divided into two paths which are polarized at a 90° angle to each other. ... 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. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ... Relative density (also known as specific gravity) is a measure of the density of a material. ...

Occurrence

Crystals have been found in stony and iron meteorites, including one that fell at Breitenhach in the Erzgebirge, Bohemia. Large crystals, a foot in length and mostly altered to steatite, were found in 1874 in the apatite veins traversing mica-schist and hornblende-schist at the apatite mine of Kjorrestad, near Brevig in southern Norway. Isolated crystals are rare, the mineral being usually found as an essential constituent of igneous rocks, either as irregular masses in plutonic rocks (norite, peridotite, pyroxenite, etc.) and the serpentines that have resulted by their alteration, or as small idiomorphic crystals in volcanic rocks (trachyte, andesite). It is also a common constituent of meteorites, forming with olivine the bulk of the material; here it often forms small spherical masses, or chondrules, with an internal radiated structure. Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... A meteorite is a small extraterrestrial body that impacts the Earths surface. ... Bohemia This article is about the historical region in central Europe; for other uses, see Bohemia (disambiguation). ... An Egyptian carved and glazed steatite scarab amulet - circa 550 BC. Steatite (ste-a-tite), also known as Potstone and Lapis ollaris is a type of soapstone which is almost purely talc. ... Apatite is a group of minerals, usually referring to: hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH-, F-, or Cl- ions, respectively, in the crystal lattice. ... rock with mica Mica sheet mica flakes The mica group of minerals includes several closely related materials having highly perfect basal cleavage. ... Categories: Mineral stubs | Metamorphic rocks ... Amphibole (Hornblende) Hornblende is a complex inosilicate series of minerals. ... Volcanic rock on North America Plutonic rock on North America Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Pluton redirects here. ... Peridotite Peridotite is a dense, coarse grained ultramafic rock, consisting mainly of the minerals olivine and pyroxene. ... Pyroxenite is a rock consisting essentially of minerals of the pyroxene group, such as augite and diallage, hypersthene, bronzite or enstatite. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe)3Si2O5(OH)4) minerals; it is also often rich in other metal ores, including chromium, manganese, cobalt and nickel. ... Trachyte is an igneous, volcanic rock with an aphanitic to porphyritic texture. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Olivine The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4 in which the ratio of magnesium and iron varies between the two endmembers of the series: forsterite (Mg-rich) and fayalite (Fe-rich). ... Chondrules in the chondrite Grassland. ...

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
• This article incorporates text from the 1911 Encyclopædia Britannica, a publication in the public domain.