Olivine
General
Category	Mineral Group
Chemical formula	(Mg, Fe)2SiO4
Identification
Color	Yellow to yellow-green
Crystal habit	Massive to granular
Crystal system	Orthorhombic
Cleavage	Poor
Fracture	Conchoidal - brittle
Mohs Scale hardness	6. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes In Mineralogy, shape and size give rise to descriptive terms applied to the typical appearance or habit of Crystals The many terms used by mineralogists A crystal system is a category of Space groups which characterize Symmetry of structures in three dimensions with Translational symmetry in three directions In Crystallography, the orthorhombic Crystal system is one of the seven Lattice Point groups Orthorhombic lattices result from stretching Cleavage, in Mineralogy, is the tendency of crystalline materials to split along definite planes creating smooth surfaces of which there are several named types In the field of Mineralogy, fracture is a term used to describe the shape and texture of the surface formed when a Mineral is broken 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 5–7
Luster	Vitreous
Refractive index	nα = 1. Lustre (or luster) is a description of the way light interacts with the surface of a Crystal, rock, or Mineral. 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 630–1. 650 nβ = 1. 650–1. 670 nγ = 1. 670–1. 690
Optical Properties	Biaxial (+)
Birefringence	δ = 0. Birefringence, or double refraction, is the decomposition of a ray of Light into two rays (the ordinary ray and the extraordinary ray 040
Streak	White
Specific gravity	3. The streak (also called powder color) of a Mineral is the Color of the powder produced when it is dragged across an unweathered surface Specific gravity is defined as the ratio of the Density of a given solid or liquid substance to the density of water at a specific temperature and pressure typically 27–3. 37
Diaphaneity	Transparent to translucent
References	[1][2]

The mineral olivine (when gem-quality also called peridot) is a magnesium iron silicate with the formula (Mg,Fe)₂SiO₄. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Peridot (pronunciation /ˈpɛrɪˌdɒt/, /ˈpɛrɪˌdoʊ/ (British English /ˈpɛərɪˌdɑt/ /ˈpɛərɪˌdɑʊ/ (US English is the gem quality variety of forsteritic Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 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 Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the It is one of the most common minerals on Earth, and has also been identified in meteorites and on the Moon, Mars, and comet Wild 2. A meteorite is a natural object originating in Outer space that survives an impact with the Earth 's surface Comet 81P/Wild, also known as Wild 2, is a Comet named after Swiss astronomer Paul Wild (pronounced Vilt) who discovered it in 1978

The ratio of magnesium and iron varies between the two endmembers of the solid solution series: forsterite (Mg-endmember) and fayalite (Fe-endmember). An endmember in Mineralogy is a Mineral that is at the extreme end of a mineral series in terms of purity A solid solution is a Solid - state Solution of one or more solutes in a Solvent. Forsterite (Mg2SiO4 is the magnesium rich end-member of the Olivine Solid solution series Fayalite (Fe2SiO4 is the Iron rich end-member of the Olivine solid-solution series Compositions of olivine are commonly expressed as molar percentages of forsterite (Fo) and fayalite (Fa) (e. g. , Fo₇₀Fa₃₀). Forsterite has an unusually high melting temperature at atmospheric pressure, almost 1900°C, but the melting temperature of fayalite is much lower (about 1200°C). The melting temperature varies smoothly between the two endmembers, as do other properties. Olivine incorporates only minor amounts of elements other than oxygen, silicon, magnesium, and iron. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Manganese and nickel commonly are the additional elements present in highest concentrations. Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28

Olivine gives its name to the group of minerals with a related structure (the olivine group) which includes tephroite (Mn₂SiO₄), monticellite (CaMgSiO₄), and kirschsteinite (CaFeSiO₄). Tephroite is a non-metallic Manganese silicate Mineral with the formula Mn 2 Si[[oxygen O]]4 that is one of the Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. Monticellite and kirschsteinite are Gray Silicate Minerals of the Olivine group with compositions Ca[[magnesium Mg]] Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Monticellite and kirschsteinite are Gray Silicate Minerals of the Olivine group with compositions Ca[[magnesium Mg]]

Identification and paragenesis

Olivine basalt

Peridotite xenoliths in basalt--olivines are light green crystals. Location: San Carlos Indian Reservation, Gila Co. , Arizona, USA.

Olivine is usually named for its typically olive-green color (thought to be a result of traces of nickel), though it may alter to a reddish color from the oxidation of iron. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 It has a conchoidal fracture and is rather brittle. Conchoidal Fracture describes the way that Brittle materials break when they do not follow any natural planes of separation. The hardness of olivine is 6. 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 5–7, its relative density is 3. Relative density, sometimes called specific density, is the Ratio of the Density of a substance to the density of a given reference material 27–3. 37, and it has a vitreous luster. Vitreous refers to a material in an Amorphous, Glassy state (in contrast to a Crystalline state Lustre (or luster) is a description of the way light interacts with the surface of a Crystal, rock, or Mineral. It is transparent to translucent.

Transparent olivine is sometimes used as a gemstone called peridot, the French word for olivine. A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive Mineral, which &mdash when cut and polished &mdash Peridot (pronunciation /ˈpɛrɪˌdɒt/, /ˈpɛrɪˌdoʊ/ (British English /ˈpɛərɪˌdɑt/ /ˈpɛərɪˌdɑʊ/ (US English is the gem quality variety of forsteritic French ( français,) is a Romance language spoken around the world by 118 million people as a native language and by about 180 to 260 million people It is also called chrysolite, from the Greek words for gold and stone. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 Some of the finest gem-quality olivine has been obtained from a body of mantle rocks on Zabargad island in the Red Sea. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided St John's Island (also known as Zagbargad Zebirget Topazios) is the largest of a group of islands in Foul Bay, Red Sea in Southern Egypt The Red Sea is a Salt water Inlet of the Indian Ocean between Africa and Asia.

Olivine/peridot occurs in both mafic and ultramafic igneous rocks and as a primary mineral in certain metamorphic rocks. Mafic is an adjective describing a Silicate mineral or rock that is rich in magnesium and iron the term was derived by contracting "magnesium" and "ferric" Ultramafic (also referred to as ultrabasic) rocks are igneous and meta -igneous rocks with very low Silica content (less than 45% generally Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Mg-rich olivine crystallizes from magma that is rich in magnesium and low in silica. Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide That magma crystallizes to mafic rocks such as gabbro and basalt. Mafic is an adjective describing a Silicate mineral or rock that is rich in magnesium and iron the term was derived by contracting "magnesium" and "ferric" Gabbro (ˈɡæbrəʊ is a dark coarse-grained intrusive Igneous rock chemically equivalent to Basalt. Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Ultramafic rocks such as peridotite, and dunite can be residues left after extraction of magmas, and typically they are more enriched in olivine after extraction of partial melts. Ultramafic (also referred to as ultrabasic) rocks are igneous and meta -igneous rocks with very low Silica content (less than 45% generally A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. Dunite (ˈduːnaɪt or /ˈdʌnaɪt/ is an igneous, Plutonic rock, of Ultramafic composition with coarse-grained or Phaneritic Olivine and high pressure structural variants constitute over 50% of the Earth's upper mantle, and olivine is one of the Earth's most common minerals by volume. The metamorphism of impure dolomite or other sedimentary rocks with high magnesium and low silica content also produces Mg-rich olivine, or forsterite. Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock)

Fe-rich olivine is relatively much less common, but it occurs in igneous rocks in small amounts in rare granites and rhyolites, and extremely Fe-rich olivine can exist stably with quartz and tridymite. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. This page is about a volcanic rock For the ghost town see Rhyolite Nevada, and for the satellite system see Rhyolite/Aquacade. Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Tridymite is a high-temperature polymorph of Quartz and usually occurs as minute tabular white or colorless pseudo-hexagonal Triclinic crystals or scales In contrast, Mg-rich olivine does not occur stably with silica minerals, as it would react with them to form orthopyroxene ((Mg,Fe)₂Si₂O₆). The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks.

Mg-rich olivine is stable to pressures equivalent to a depth of about 410 km within Earth. Because it is thought to be the most abundant mineral in Earth’s mantle at shallower depths, the properties of olivine have a dominant influence upon the rheology of that part of Earth and hence upon the solid flow that drives plate tectonics. Rheology is the study of the flow of matter mainly liquids but also soft solids or solids under conditions in which they flow rather than deform elastically Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere Experiments have documented that olivine at high pressures (e. g. , 12 GPa, the pressure at depths of 360 kilometers or so) can contain at least as much as about 8900 parts per million (weight) of water, and that such water contents drastically reduce the resistance of olivine to solid flow; moreover, because olivine is so abundant, more water may be dissolved in olivine of the mantle than contained in Earth’s oceans. ^[3]

Mg-rich olivine has also been discovered in meteorites, on Mars, and on Earth's moon. A meteorite is a natural object originating in Outer space that survives an impact with the Earth 's surface Such meteorites include chondrites, collections of debris from the early solar system, and pallasites, mixes of iron-nickel and olivine. Chondrites are stony Meteorites that have not been modified due to Melting or Differentiation of the parent body A pallasite is a type of stony-iron Meteorite. It consists of cm-sized Olivine crystals of Peridot quality in an iron- Nickel matrix The spectral signature of olivine has been seen in the dust disks around young stars. The tails of comets (which formed from the dust disk around the young Sun) often have the spectral signature of olivine, and the presence of olivine has recently been verified in samples of a comet from the Stardust spacecraft. The Sun (Sol is the Star at the center of the Solar System. Stardust is an American interplanetary mission of the NASA Jet Propulsion Laboratory, whose primary purpose was to investigate the makeup of the ^[4]

Crystal structure

Figure 1: The atomic scale structure of olivine looking along the a axis. Oxygen is shown in red, silicon in pink, and magnesium/iron in blue. A projection of the unit cell is shown by the black rectangle

Minerals in the olivine group crystallize in the orthorhombic system (space group Pbnm) with isolated silicate tetrahedra, meaning that olivine is a nesosilicate. In Crystallography, the orthorhombic Crystal system is one of the seven Lattice Point groups Orthorhombic lattices result from stretching The space group of a Crystal or crystallographic group is a mathematical description of the Symmetry inherent in the structure 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 In an alternative view, the atomic structure can be described as a hexagonal, close-packed array of oxygen ions with half of the octahedral sites occupied with magnesium or iron ions and one-eighth of the tetrahedral sites occupied by silicon ions. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge

There are three distinct oxygen sites (marked O1, O2, and O3 in figure 1), two distinct metal sites (M1 and M2), and only one distinct silicon site. O1, O2, M2, and Si all lie on mirror planes, while M1 exists on an inversion center. In Mathematics, a reflection (also spelled reflexion) is a map that transforms an object into its Mirror image. O3 lies in a general position.

High pressure polymorphs

At the high temperatures and pressures found at depth within the Earth the olivine structure is no longer stable. Below depths of about 410 km olivine undergoes a phase transition to the sorosilicate, wadsleyite and, at about 520 km depth, wadsleyite transforms into ringwoodite, which has the spinel structure. In Thermodynamics, phase transition or phase change is the transformation of a thermodynamic system from one phase to another 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 Wadsleyite is a high-pressure Polymorph of Olivine, an Orthorhombic Mineral found in the Peace River Meteorite in Alberta Canada Ringwoodite is a high-pressure Polymorph of Olivine, and it is stable at high temperatures and pressures like those in the Earth's mantle near 600 km depth The spinels are any of a class of Minerals of general formulation XY2 O 4 which Crystallize in the cubic (isometric These phase transitions lead to a discontinuous increase in the density of the Earth's mantle that can be observed by seismic methods. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided Seismology (from Greek grc σεισμός seismos, "earthquake" and grc -λογία -logia) is the scientific study of Earthquakes

The pressure at which these phase transitions occur depends on temperature and iron content (Deer et al. 1992). At 800°C the pure magnesium end member, forsterite, transforms to wadsleyite at 11. 8 gigapascals (118 kbar) and to ringwoodite at pressures above 14 GPa (140 kbar). Increasing the iron content decreases the pressure of the phase transition and narrows the wadsleyite stability field. Wadsleyite is a high-pressure Polymorph of Olivine, an Orthorhombic Mineral found in the Peace River Meteorite in Alberta Canada At about 0. 8 mole fraction fayalite, olivine transforms directly to ringwoodite over the pressure range 10–11. In Chemistry, the mole fraction of a component in a Mixture is the relative proportion of molecules belonging to the component to those in the mixture 5 GPa (100–115 kbar). Fayalite transforms to Fe₂SiO₄ spinel at pressures below 5 GPa (50 kbar). Increasing the temperature increases the pressure of these phase transitions.

Historical and mythical uses

The Septuagint names chrysolithos as a stone on the Hoshen in the verse Exodus 28:20; the masoretic text has the word tarshish, which has uncertain meaning, in the same place. The Septuagint (ˈsɛptuədʒɪnt or simply " LXX " is the Koine Greek version of the Hebrew Bible, translated in stages between the Hoshen / Choshen is a Hebrew word usually translated as breastplate; in English language contexts it refers to a specific Breastplate Exodus ( Greek: έξοδος eksodos = "departure" is the second book of the Jewish Torah and of the Christian Old Testament. The Masoretic Text ( MT) is the Hebrew text of the Jewish Bible ( Tanakh) According to the New International Version and Rebbenu Bachya, the word tarshish refers to chrysolite (olivine) and Rebbenu Bachya claims it was the stone representing the tribe of Asher. The New International Version is an English Translation of the Christian Bible. Bahye ben Asher ( Hebrew: בחיי בן אשר) or Bahye ben Asher ben Halawa also known as the Rabbeinu Behaye, born about the middle of the Asher ( in the Book of Genesis, is the second son of Jacob and Zilpah, and the founder of the Tribe of Asher. However, Chrysolite took its modern meaning much more recently, and in Greek times just meant golden stone (chryso-lithos), and could refer not only to yellowish olivine, but also to Topaz, Amber, yellow Jasper, yellow Serpentine, or even lapis lazuli which has golden flecks within its mainly blue surface and fits with the targum descriptions of the tarshish stone as being sea-colored. Topaz is a Silicate mineral of Aluminium and Fluorine with the Chemical formula Al 2 Si[[oxygen O]]4( Amber is Fossil tree Resin, which is appreciated for its color and beauty JasPer is a project to create a reference implementation of the codec specified in the JPEG-2000 Part-1 standard (ie The serpentine group describes a group of common rock-forming hydrous Magnesium Iron phyllosilicate (()3 Minerals they A targum ( Hebrew: תרגום plural targumim, lit "translation interpretation" is an Aramaic Translation of the Hebrew Tarshish probably refers to Tarshish, a place, though this doesn't identify the stone much more. Tarshish occurs in the Hebrew Bible with these meanings One of the sons of Javan (Genesis 104 In the Biblical account, there is a stone, on an earlier row, that scholars think was translucent and yellow, so scholars think that chrysolithos/tarshish here is unlikely to refer to olivine, because that would place two translucent stones next to each other, and be quite jarring; instead scholars favour yellow Jasper or Serpentine. There is a wide range of views among traditional sources about which tribe the stone refers to.

Uses

A worldwide search is on for cheap processes to sequester CO₂ by mineral reactions. Removal by reactions with olivine is an attractive option, because it is widely available and reacts easily with the (acid) CO₂ from the atmosphere. When olivine is crushed, it weathers completely within a few years, depending on the grain size. All the CO₂ that is produced by burning 1 liter of oil can be sequestered by less than 1 liter of olivine. The reaction is exothermic but slow. In order to recover the heat produced by the reaction to produce electricity, a large volume of olivine must be thermally well isolated. Then it can produce power, while at the same time removing CO₂. The end-products of the reaction are silicon dioxide, magnesium carbonate and small amounts of iron oxide.

See also

• List of minerals
• Bowen's reaction series

References

1. ^ http://webmineral.com/data/Olivine.shtml Webmineral
2. ^ http://www.mindat.org/min-2983.html Mindat
3. ^ Smyth, J. This is a List of Minerals for which there are Wikipedia articles Within the field of Geology, Bowen's reaction series is the work of the Petrologist, Norman L R. , Frost, D. J. , Nestola, F. , Holl, C. M. , Bromiley, G. , Olivine hydration in the deep upper mantle: Effects of temperature and silica activity. Geophysical Research Letters, v. 33, L15301, doi:10. 1029/2006GL026194, 2006
4. ^ Press Release 06-091. Jet Propulsion Laboratory Stardust website, retrieved May 30, 2006.

• Klein, Cornelis; and C. S. Hurlburt (1985). Manual of Mineralogy (21rst ed. ). New York: John Wiley & Sons, 681 pp. ISBN 0-471-80580-7.  

• Deer, W. A. ; R. A. Howie, and J. Zussman (1992). An Introduction to the Rock-Forming Minerals (2nd ed. ). London: Longman, 696 pp. ISBN 0-582-30094-0.