Image Chiastolit.jpg thumb 300px The mineral chiastolite is a variety of andalusite with the chemical composition Al sub 2 sub SiO sub 5 sub . It is noted for distinctive cross shaped black inclusions of graphite . In areas around Georgetown, California , metamorphosed sediments contained andalusite and chiastolite in a graphite rich metasediment. The chiastolite crystals have been pseudomorph pseudomorphically altered by a mixture of muscovite , paragonite and margarite . The calcium rich margarite tends to form along the graphite rich crosses or bands within the chiastolite. Mineralogically the occurrence is important because all three white mica phases are present in an equilibrium assemblage. References http www.mindat.org min 1001.html Mindat with location data http www.minsocam.org ammin AM64 AM64 728.pdf Margarite pseudomorphs after chiastolite in the Georgetown area, California, Am. Mineralogist 1979 PDF Category Aluminium minerals Category Nesosilicates Category Orthorhombic minerals silicate mineral stub fa hr Hijastolit nl Chiastoliet pl Chiastolit sh Hijastolit ... more details
File QuartzFantome.jpg thumb Phantom crystal of quartz Phantom quartz is a variety of quartz , or rock crystal , that, over the course of millions of years, forms over earlier rock crystals that already existed. It takes its name from the particular structure of its crystallization each crystal displays the outlines of numerous smaller crystals, known as phantoms. It is found in Austria, Brazil, Madagascar, Switzerland, and the United States. Like regular quartz, the chemical composition of phantom quartz is silicon oxygen 2 , and its Mohs scale of mineral hardness hardness is 7. The available forms of phantom quartz are crystal groups, single crystals, crystal points, touchstone, tumbled stones as a jewelry gemstone, usually found in the form of as pendant. The crystallization is a trigonal crystal. See also Pseudomorph References reflist External links http www.quartzpage.de gro text.html The Quartz Page, Growth Forms, Phantom Quartz Category Quartz varieties mineral stub ... more details
one source date January 2011 Itabirite , also known as banded quartz hematite and hematite schist , is a laminated, metamorphosed oxide facies iron formation in which the original chert or jasper bands have been recrystallized into megascopically distinguishable grains of quartz and the iron is present as thin layers of hematite, magnetite , or martite pseudomorph s of hematite after magnetite . ref name US Bureau of Mines http www.arizonagoldprospectors.com Mining Dictionary index.html US Bureau of Mines Dictionary of Mining, Mineral, and Related Terms. Accessed 12 December 2010 ref The term was originally applied in Itabirito Pico de Itabirito , in the state of Minas Gerais and southern part of Belo Horizonte , Brazil , to a high grade, massive specular hematite ore 66 iron associated with a schistose rock composed of granular quartz and scaly hematite. The term is now widely used outside Brazil. ref http vsites.unb.br ig sigep sitio042 sitio042english.pdf Carlos Alberto Rosi re et al. Itabira Peak, State of Minas Gerais. Geographic, historical and structural landmark of the Quadril tero Ferr fero . In S tios Geol gicos e Paleontol gicos do Brasil SIGEP 042, 2005 ref References references Category Geology of Brazil Category Iron mining pt Itabirito geologia ... more details
the alteration of other minerals, it has been known to form pseudomorph s of many different minerals. A pseudomorph is a mineral that has replaced another mineral atom by atom, but it leaves the original ... more details
Infobox mineral name Shattuckite category Inosilicate image Shattuckite 170581.jpg caption Shattuckite from the type locality in Bisbee. Size 6.0 4.9 2.9 cm. strunz 09.DB.40 formula Cu sub 5 sub SiO sub 3 sub sub 4 sub OH sub 2 sub molweight color Dark and light blue, turquoise habit Commonly spherulitic aggregates of acicular crystals system Orthorhombic twinning cleavage perfect along 010 and 100 fracture uneven mohs 3.5 luster Dull to silky refractive n sub sub 1.753, n sub sub 1.782, n sub sub 1.815 opticalprop Biaxial birefringence pleochroism X very pale blue Y pale blue Z deep blue streak Blue gravity 4.1 rather heavy for a non metallic mineral melt fusibility diagnostic solubility diaphaneity Translucent to opaque other references ref name Webmin http webmineral.com data Shattuckite.shtml Shattuckite . Webmineral.com. Retrieved on 2011 10 10. ref ref name Mindat http www.mindat.org min 3634.html Shattuckite . Mindat.org 2011 09 08 . Retrieved on 2011 10 10. ref ref name HBM http rruff.geo.arizona.edu doclib hom shattuckite.pdf Shattuckite . Handbook of Mineralogy. PDF . Retrieved on 2011 10 10. ref Shattuckite is a copper Silicate minerals silicate hydroxide mineral with formula Cu sub 5 sub SiO sub 3 sub sub 4 sub OH sub 2 sub . It crystallizes in the orthorhombic dipyramidal crystal system and usually occurs in a granular massive form and also as fibrous acicular crystals. It is closely allied to plancheite in structure and appearance. Shattuckite is a relatively rare copper silicate mineral. It was first discovered in 1915 in the copper mines of Bisbee, Arizona , specifically the Shattuck Mine hence the name . It is a secondary mineral that forms from the alteration of other secondary minerals. At the Shattuck Mine, it forms pseudomorph s after malachite . A pseudomorph is an atom by atom replacement of a crystal structure by another crystal structure, but with little alteration of the outward shape of the original crystal. Gallery gallery widths 20 ... more details
Infobox mineral name Bertrandite boxwidth boxbgcolor image Bertrandite Hydrous Berylium Silicate Governour Valadares Minas Gerais Brazil 1961.jpg imagesize alt caption Bertrandite from Brazil category Silicate minerals sorosilicate formula Be sub 4 sub Si sub 2 sub O sub 7 sub OH sub 2 sub strunz dana symmetry unit cell molweight color colour habit system twinning cleavage fracture tenacity mohs luster streak diaphaneity gravity density polish opticalprop refractive birefringence pleochroism 2V dispersion extinction length fast slow fluorescence absorption melt fusibility diagnostic solubility impurities alteration other prop1 prop1text references Bertrandite is a beryllium Silicate minerals sorosilicate hydroxide mineral with composition Be sub 4 sub Si sub 2 sub O sub 7 sub OH sub 2 sub . Bertrandite is a colorless to pale yellow orthorhombic mineral with a Mohs hardness hardness of 6 7. It is commonly found in beryllium rich pegmatite s and is in part an alteration of beryl . Bertrandite often occurs as a pseudomorph ic replacement of beryl. It, with beryl, are ores of beryllium. It was discovered near Nantes, France in 1883 and named after France French mineralogist , Emile Bertrand 1844 1909 . ref http rruff.geo.arizona.edu doclib hom bertrandite.pdf Handbook of Mineralogy ref ref http www.mindat.org min 642.html Mindat ref ref http webmineral.com data Bertrandite.shtml Webmineral ref See also List of minerals List of minerals named after people References commons category Bertrandite Reflist Category Beryllium minerals Category Sorosilicates Category Orthorhombic minerals silicate mineral stub fa fr Bertrandite it Bertrandite nl Bertrandiet pt Bertrandita ru uk ... more details
Infobox mountain name Payun Matru photo Payunmatru.jpg photo caption Payun Matru from Space elevation m 3680 elevation ref prominence location Argentina range Andes coordinates coord 36.42 S 69.20 W format dms type mountain region AR display inline,title topo type Shield volcano age last eruption Unknown first ascent easiest route File Hematite Magnetite 160168.jpg thumb 180px Hematite after magnetite, Pay n volcano. Size 8.3 x 3.1 x 2.3 cm. Payun Matru is a shield volcano in Argentina , located in the Reserva Provincial La Payunia of the Malarg e Department , to the south of the Mendoza Province . Volcan Payun is notable for large crystals of hematite pseudomorph s after magnetite , of volcanic fumarole origin. ref http www.mindat.org loc 7958.html Payun volcano at Mindat.org ref See also List of volcanoes in Argentina References cite gvp vnum 1507 066 name Pay n Matru reflist Commons category Minerals of Payun volcano External links http earthobservatory.nasa.gov IOTD view.php?id 77039&src eorss iotd Pay n Matru Volcanic Field, Argentina Image of the Day at NASA s Earth Observatory Category Shield volcanoes Category Subduction volcanoes Category Mountains of Argentina Category Volcanoes of Argentina Category Geography of Mendoza Province Category Polygenetic volcanoes MendozaAR geo stub es Pay n Matr fr Pay n Matr ka qu Payun Matru sk Pay n Matru sv Pay n Matr ... more details
Infobox mineral name Mottramite boxwidth boxbgcolor image Mottramite.jpg imagesize alt caption Mottramite yellow with fluorite and quartz. From Lower Silesia , Poland. category Vanadate minerals formula PbCu VO sub 4 sub OH strunz 08.BH.40 dana symmetry mmm 2 m 2 m 2 m Dipyramidal unit cell a 7.68 , b 9.27 , c 6.03 molweight color Grass green, olive green, yellow green, siskin green, blackish brown, nearly black colour habit system Orthorhombic twinning cleavage None observed fracture Irregular uneven, sub conchoidal tenacity Brittle mohs 3 3 luster Greasy streak Yellowish green diaphaneity Transparent, opaque gravity 5.9 density polish opticalprop Biaxial refractive n sub sub 2.170 2 n sub sub 2.260 2 n sub sub 2.320 2 birefringence 0.150 pleochroism Visible 2V Measured 73 , Calculated 46 dispersion strong r v rarely r v extinction length fast slow fluorescence absorption melt fusibility diagnostic solubility impurities alteration other prop1 prop1text references Mottramite is an orthorhombic mineral , lead Pb copper Cu vanadium V oxygen O sub 4 sub O hydrogen H , at the copper end of the descloizite group. It was formerly called cuprodescloizite or psittacinite this mineral characterized in 1868 by Frederick Augustus Genth . Gallery gallery widths 220px heights 220px File Copper Mottramite rut323b.jpg Pseudomorph of Mottramite after dendritic Copper, Tsumeb mine , Namibia. Size 3.1 x 1.2 x .2 cm. File Mottramit Mineralogisches Museum Bonn 7284 .jpg Mottramite, Olifantsfontain, Namibia gallery References http www.mindat.org min 2792.html Mindat.org http webmineral.com data Mottramite.shtml Webmineral.com http mineral.galleries.com minerals phosphat mottrami mottrami.htm Mineral galleries Commons Category Vanadate minerals Category Copper minerals Category Lead minerals Category Descloizite group Category Orthorhombic minerals mineral stub ca Mottramita de Mottramit el fa it Mottramite he nl Mottramiet pl Mottramit ro Mottramit ... more details
Infobox mineral name Weddellite category Organic compounds boxwidth boxbgcolor image Weddellite.jpg caption formula Oxalate Oxalic acid Calcium oxalate dihydrate CaC sub 2 sub O sub 4 sub · 2H sub 2 sub O molweight strunz 10.AB.40 color Yellowish brown habit eight face bi pyramid typical system Tetragonal twinning yes cleavage OUI fracture Conchoidal mohs 4 luster Vitreous Glassy refractive 1.52 1.54 DR 0.009 B G interval opticalprop birefringence pleochroism streak White gravity melt fusibility diagnostic solubility diaphaneity other Weddellite calcium Ca carbon C sub 2 sub oxygen O sub 4 sub 2 water H sub 2 sub O is a mineral form of calcium oxalate named for occurrences of millimeter sized crystals found in bottom sediments of the Weddell Sea , off Antarctica . Occasionally, weddellite partially dehydrates to whewellite , forming excellent pseudomorph s of grainy whewellite after weddellite s short tetragonal dipyramids. Structural properties The weddellite or calcium oxalate di hydrate crystallizes in the tetragonal system. The classic crystal shape is the eight face bi pyramid. In bright field microscopy, the weddellite crystals are recognized easily by their shape that reminds a mail envelope. More complex shapes of weddellite are possible. The dumbbell shape is not rare. The former has no precise angles or sides. This form is, in reality, a microcrystalline agglomerate that takes the shape of a biconcave disc. Weddellite crystals are poorly birefringent and do not show any interference pattern under polarized light . Biological role Weddellite crystals are usually of little clinical value. Many specimens develop weddellite crystals on standing. Together, whewellite and weddellite are the most common renal calculi . File Surface of a kidney stone.jpg thumb Scanning Electron Micrograph of the surface of a kidney stone showing crystals of Weddellite calcium oxalate dihydrate emerging from the amorphous central part of the stone. Horizontal length of the pi ... more details
Infobox mineral name Metatorbernite category Phosphate minerals boxwidth boxbgcolor image Metatorbernite.jpg caption Green platy crystals on granite . Specimen from Redruth , Cornwall , UK formula Copper Cu Uranium U Oxygen O sub 2 sub sub 2 sub Phosphorus P Oxygen O sub 4 sub sub 2 sub 8 Hydrogen H sub 2 sub Oxygen O molweight strunz 08.EB.10 color Light to dark green habit Flat plates system Tetragonal dipyramidal twinning cleavage Perfect fracture Brittle mohs 2.5 luster Vitreous, adamantine refractive 1.624 1.626 opticalprop birefringence pleochroism streak Light green gravity 3.7 3.8 melt fusibility diagnostic solubility diaphaneity other Image Radioactive.svg 25px Radioactive Metatorbernite or meta torbernite is a radioactive decay radioactive phosphate minerals phosphate mineral , and is a dehydration pseudomorph of torbernite . Chemically, it is a copper uranyl phosphate and usually occurs in the form of green platy deposits. It can form by direct deposition from a supersaturation supersaturated solution, which produces true crystalline metatorbernite, with a dark green colour, translucent diaphaneity , and vitreous lustre. However, more commonly, it is formed by the dehydration of torbernite, which causes internal stress and breakage within the crystal structure crystal lattice , resulting in crystals composed of microscopic powder held together using Electrostatics electrostatic force, and having a lighter green colour, opaque diaphaneity, and a relatively dull lustre. As with torbernite, it is named after the Sweden Swedish chemist Tornbern Bergmann . It is especially closely associated with torbernite, but is also found amongside autunite , meta autunite and uraninite . References http www.mindat.org min 2689.html MinDAT http webmineral.com data Metatorbernite.shtml Webmineral http www.uraniumminerals.com UTh M Torbernite.htm Uranium minerals File Metatorbernite sapin.jpg thumb left Metatorbernite from the Margabal Mine, Entraygues sur Truy re , France. ... more details
Infobox mineral name Tincalconite boxwidth boxbgcolor image TincalconiteUSGOV.jpg imagesize alt caption Tincalconite category Nesoborates formula Na sub 2 sub B sub 4 sub O sub 5 sub O hydrogen H sub 4 sub sub sub 3H sub 2 sub O strunz 06.DA.15 dana symmetry unit cell molweight color colour habit system twinning cleavage fracture tenacity mohs luster streak diaphaneity gravity density polish opticalprop refractive birefringence pleochroism 2V dispersion extinction length fast slow fluorescence absorption melt fusibility diagnostic solubility impurities alteration other prop1 prop1text references Image Tincalconite byu.jpg thumb right 300px Tincalconite , Boron, California Tincalconite is a hydrous sodium borate mineral closely related to borax , and is a secondary mineral that forms as a dehydration product of borax. Its formula is sodium Na sub 2 sub boron B sub 4 sub oxygen O sub 7 sub 5 water H sub 2 sub O or Na sub 2 sub B sub 4 sub O sub 5 sub O hydrogen H sub 4 sub sub sub 3H sub 2 sub O. Tincalconite typically occurs as a fine grained white powder. It crystallizes in the Hexagonal crystal system hexagonal crystal system and has been found as primary euhedral di rhombohedral, pseudo octahedral crystals. It is also found pseudomorph ically replacing borax crystals. It has a specific gravity of 1.88 and a Mohs hardness of 2. Refractive index values are n 1.460 and n 1.470. While most tincalconite is created by man through exposing borax to dry air, there are natural occurrences of tincalconite, as in Searles Lake , California where it was first described in 1878. In addition to several California and Nevada locations it is reported from Argentina, Italy, Turkey and Ukraine. The name comes from tincal , Sanskrit for borax, and Greek, konis , meaning powder, for its composition and typical powdery nature. align center class wikitable center Image Tincalconite unit cell 3D balls.png 250px center center small Ball and stick model of the unit cell of tincalconite s ... more details
Infobox mineral name Eucryptite category Silicate mineral image Eucryptite 202043.jpg imagesize caption Eucryptite grains in albite from the type locality size 9.3 x 7.0 x 2.8 cm formula LiAlSiO sub 4 sub symmetry Trigonal overline 3 unit cell a 13.48 , c 9.01 Z 18 color Brown, colorless, white habit Rare as euhedral crystals, coarse crystalline aggregates and massive system Trigonal crystal system Trigonal rhombohedral cleavage Indistinct on 10 overline 1 0 and 0001 fracture Conchoidal tenacity Very brittle mohs 6.5 luster Vitreous refractive n sub sub 1.570 1.573 n sub sub 1.583 1.587 opticalprop Uniaxial birefringence 0.013 streak White density 2.67 diaphaneity Transparent to translucent other Fluoresces pink to red or orange under SW UV references ref name Mindat http www.mindat.org min 1364.html Mindat.org ref ref name Handbook http rruff.geo.arizona.edu doclib hom eucryptite.pdf Handbook of Mineralogy ref ref http webmineral.com data Eucryptite.shtml Webmineral data ref Eucryptite is a lithium bearing aluminium silicate minerals silicate mineral with formula LiAlSiO sub 4 sub . It crystallizes in the Trigonal crystal system trigonal rhombohedral crystal system . It typically occurs as granular to massive in form and may pseudomorph ically replace spodumene. It has a brittle to conchoidal fracture and indistinct cleavage. It is transparent to translucent and varies from colorless to white to brown. It has a Mohs hardness of 6.5 and a specific gravity of 2.67. Optically it is uniaxial positive with refractive index values of n 1.570 1.573 and n 1.583 1.587. Its typical occurrence is in lithium rich pegmatite s in association with albite , spodumene , petalite , amblygonite , lepidolite and quartz . ref name Handbook It occurs as a secondary alteration product of spodumene . It was first described in 1880 for an occurrence at its Type locality geology type locality , Branchville, Connecticut . ref name Mindat Its name was from the Greek language Greek ... more details
This article refers about a member of the mica group, and should not be confused with Margarita disambiguation margarita . Infobox mineral name Margarite boxwidth boxbgcolor image Margarite 181325.jpg imagesize alt caption Margarite from the Wright Mine, Chester Emery Mines, Chester, Hampden County, Massachusetts, USA. Size 4.8 x 3.4 x 2.6 cm. category Micas Silicate minerals phyllosilicates formula CaAl sub 2 sub Al sub 2 sub Si sub 2 sub O sub 10 sub OH sub 2 sub strunz 09.EC.30 dana symmetry unit cell molweight color colour habit system twinning cleavage fracture tenacity mohs luster streak diaphaneity gravity density polish opticalprop refractive birefringence pleochroism 2V dispersion extinction length fast slow fluorescence absorption melt fusibility diagnostic solubility impurities alteration other prop1 prop1text references Margarite is a calcium rich member of the mica group of the Silicate minerals phyllosilicates with formula calcium Ca aluminum Al sub 2 sub Al sub 2 sub silicon Si sub 2 sub oxygen O sub 10 sub O hydrogen H sub 2 sub . It forms white to pinkish or yellowish gray masses or thin laminae. It crystallizes in the monoclinic crystal system . It typically has a specific gravity of around 3 and a Mohs hardness of 4. It is translucent with perfect 010 cleavage and exhibits crystal twinning . It occurs commonly as an alteration product of corundum , andalusite and other aluminous minerals. It has been reported as forming alteration pseudomorph s of chiastolite along with muscovite and paragonite . The margarite in this occurrence forms preferentially along the dark graphite rich inclusions with the chiastolite crystals. References commonscat Margarite Refbegin Deer, W.A., R.A. Howie, and J. Zussman 1963 Rock forming minerals, v. 3, Sheet Silicates, p. 95 98. http www.mindat.org min 2573.html Mindat with location data http www.webmineral.com data Margarite.shtml Webmineral data http rruff.geo.arizona.edu doclib hom margarite.pdf Mineral Data Publish ... more details
Commented out because image was deleted Image Santabarbaraite.jpg thumb The Mineral Infobox mineral name Santabarbaraite category Phosphate minerals boxwidth boxbgcolor formula Fe sub 3 sub sup 3 sup PO sub 4 sub sub 2 sub OH sub 3 sub 5H sub 2 sub O molweight strunz 08.CE.80 color Brown light Brown habit Elongated or flattened prisms system Amorphous twinning None cleavage None, Parting along 010 of replaced phase fracture Conchoidal mohs Not determined luster Vitreous Greasy refractive n 1.659 opticalprop isotropic birefringence pleochroism streak yellow umber gravity 2.24 density melt fusibility diagnostic solubility diaphaneity Translucent other Pseudomorphism references ref http www.mindat.org min 11436.html Santabarbaraite Santabarbaraite mineral information and data Bot generated title ref ref http www.webmineral.com data Santabarbaraite.shtml Santabarbaraite Mineral Data Bot generated title ref Santabarbaraite is an amorphous ferric hydroxy phosphate mineral hydrate that was discovered in Tuscany , Italy in 2000. ref name Pratesi Pratesi G., Cipriani C., Guili G., and Birch W. D. 2003 Santabarbaraite a new amorphous phosphate mineral. European Journal of Mineralogy . 15 , 185 192 ref It also can be found in Victoria, Australia and Lake Baikal , Siberia . ref name Fagel Fagel N., Alleman L. Y., Granina L., Hatert F., Thamo Bozso E., Cloots R. and Andre L. 2005 Vivianite formation and distribution in Lake Baikal sediments. Global and Planetary Change . 46 , 315 336 ref This phosphate mineral has a simplified formula Fe sub 3 sub sup 3 sup PO sub 4 sub sub 2 sub OH sub 3 sub 5H sub 2 sub O, ref name Pratesi which is the same formula of another non amorphous phosphate mineral called allanpringite. ref Kolitsch U., Bernhardt H. J., Lengauer C. L., Blass G. and Tillmanns E. 2006 Allanpringite, Fe3 PO4 2 OH 3 5H2O, a new ferric iron phosphate from Germany, and its close relation to wavellite. European Journal of Mineralogy . 18 , 793 801 ref Santabarbaraite occurs ... more details
geological time through the presence of pseudomorph s of other calcium carbonate phases after ... White Sea hornlets, White Sea and Kola peninsula. Ikaite or its pseudomorph s have been reported as occurring ... more details
other uses Pseudomorph Keep this note Technical term, necessary for Wikipedia articles don t assign for wiktionary In linguistics , an allomorph is a variant form of a morpheme . The concept occurs when a unit of meaning can vary in sound without changing meaning. The term allomorph explains the comprehension of phonological variations for specific morphemes. Allomorphy in English suffixes English has several morphemes that vary in sound but not in meaning. Examples include the past tense and the plural morphemes. For example, in English language English , a past tense morpheme is ed . It occurs in several allomorphs depending on its phonological environment, assimilating voicing of the previous segment or inserting a schwa when following an alveolar stop as IPA d or IPA d in verbs whose Word stem stem ends with the alveolar stops IPA t or IPA d , such as hunted IPA h nt d or banded IPA b nd d as IPA t in verbs whose stem ends with voiceless phonemes other than IPA t , such as fished IPA f t as IPA d in verbs whose stem ends voiced phonemes other than IPA d , such as buzzed IPA b zd Notice the other than restrictions above. This is a common fact about allomorphy if the allomorphy conditions are ordered from most restrictive in this case, after an alveolar stop to least restrictive, then the first matching case usually wins . Thus, the above conditions could be re written as follows as IPA d or IPA d when the stem ends with the alveolar stops IPA t or IPA d as IPA t when the stem ends with voiceless phonemes as IPA d elsewhere The fact that the IPA t allomorph does not appear after stem final IPA t , despite the fact that the latter is voiceless, is then explained by the fact that IPA d appears in that environment, together with the fact that the environments are ordered. Likewise, the fact that the IPA d allomorph does not appear after stem final IPA d is because the earlier clause for the IPA d allomorph takes priority and the fact that the IPA d allomorph does ... more details
about the gemstone the characters in the Sailor Moon series Amazon Trio Infobox mineral name Tiger s Eye image Tig.jpg alt A photograph showing a polished reddish brown stone which is bisected by a band containing golden fibers caption Polished tiger s eye gemstone formula Silica silicon dioxide , SiO sub 2 sub color golden to red brown habit system twinning cleavage fracture mohs 7.0 luster Silky refractive opticalprop birefringence fluorescence pleochroism streak gravity 2.64 2.71 Tiger s eye also called Tigers eye or Tiger eye is a Chatoyancy chatoyant gemstone that is usually a metamorphic rock that is a golden to red brown color, with a silky Lustre mineralogy luster . A member of the quartz group, it is a classic example of pseudomorph ous replacement by silica of fibrous crocidolite blue asbestos . An incompletely silicified blue variant is called Hawk s eye . Cut, treatment, and imitation stack begin float left clear true File Quartz Tigers Eye raw stone from Southafrica.jpg thumb left alt Photograph of a chunk of rock containing horizontal bands which contain golden fibers which are positioned vertically within the bands Unpolished Tiger eye from South Africa File Tigers eye egg shape.jpg thumb left alt Photograph of a polished ovoid stone with bands containing shimmering golden fibers Egg shape tiger s eye with iron stripes stack end The gems are usually cut Cabochon en cabochon in order to best display their chatoyancy . Red stones are brought about through gentle heat treatment. Dark stones have had their colors improved and been artificially lightened using nitric acid treatments. ref cite book last O Donoghue first Michael title Synthetic, Imitation, and Treated Gemstones year 1997 publisher Butterworth Heinemann location Boston, Massachusetts isbn 0 7506 3173 2 pages 125 127 ref Honey colored stones have been used to imitate the much higher valued cat s eye chrysoberyl cymophane , but the overall effect is unconvincing. Artificial optical fiber fibero ... more details
infobox mineral name Dumortierite category Boro silicate mineral boxwidth boxbgcolor image Dumortierite ch23a.jpg imagesize alt caption Dumortierite from Alpine County, California , USA, possibly pseudomorph ic after tourmaline size 5.7 x 2.7 x 1.1 cm formula Al sub 7 sub BO sub 3 sub SiO sub 4 sub sub 3 sub O sub 3 sub or Al sub 6.5 7 sub BO sub 3 sub SiO sub 4 sub sub 3 sub O,OH sub 3 sub ref name Webmin strunz dana symmetry Orthorhombic 2 m 2 m 2 m unit cell a 11.77 ngstrom , b 20.21 , br c 4.71 Z 4 molweight color Blue, greenish blue, violet blue, pale blue, red colour habit As fibrous or columnar crystals coarsely crystalline to intimate parallel aggregates of needles massive system Orthorhombic Dipyramidal twinning Common on 110 , may produce trillings cleavage Distinct on 100 , poor on 110 parting on 001 fracture Fibrous tenacity mohs 7 8.5 luster Vitreous to dull streak White diaphaneity Transparent to translucent gravity 3.3 3.4 density polish opticalprop Biaxial refractive n sub sub 1.659 1.678 n sub sub 1.684 1.691 n sub sub 1.686 1.692 birefringence 0.027 pleochroism Strong X deep blue or violet Y yellow to red violet or nearly colorless Z colorless or very pale blue 2V Measured 20 to 52 , Calculated 30 dispersion r v strong extinction length fast slow fluorescence absorption melt fusibility diagnostic solubility other alteration references ref name Webmin http webmineral.com data Dumortierite.shtml Webmineral data ref ref name Handbook http rruff.geo.arizona.edu doclib hom dumortierite.pdf Handbook of Mineralogy ref ref name Mindat http www.mindat.org min 1329.html Mindat.org ref Dumortierite is a fibrous variably colored aluminium Boron boro Silicate minerals silicate mineral, Al sub 7 sub BO sub 3 sub SiO sub 4 sub sub 3 sub O sub 3 sub . Dumortierite crystallizes in the orthorhombic system typically forming fibrous aggregates of slender Prism geometry prismatic crystal s. The crystals are vitreous and vary in color from b ... more details
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