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Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium-sodium) feldspars. Feldspars make up about 60% of the Earth's crust, and 41% of the Earth's continental crust by weight.
Orthoclase, or orthoclase feldspar (endmember formula KAlSi3O8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for "straight fracture", because its two cleavage planes are at right angles to each other. It is a type of potassium feldspar, also known as K-feldspar. The gem known as moonstone (see below) is largely composed of orthoclase.
Anorthite is the calcium endmember of the plagioclase feldspar mineral series. The chemical formula of pure anorthite is CaAl2Si2O8. Anorthite is found in mafic igneous rocks. Anorthite is rare on the Earth but abundant on the Moon.
Coffinite is a uranium-bearing silicate mineral with formula: U(SiO4)1−x(OH)4x.
Illite is a group of closely related non-expanding clay minerals. Illite is a secondary mineral precipitate, and an example of a phyllosilicate, or layered alumino-silicate. Its structure is a 2:1 sandwich of silica tetrahedron (T) – alumina octahedron (O) – silica tetrahedron (T) layers. The space between this T-O-T sequence of layers is occupied by poorly hydrated potassium cations which are responsible for the absence of swelling. Structurally, illite is quite similar to muscovite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer potassium. The chemical formula is given as (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2·(H2O)], but there is considerable ion (isomorphic) substitution. It occurs as aggregates of small monoclinic grey to white crystals. Due to the small size, positive identification usually requires x-ray diffraction or SEM-EDS analysis. Illite occurs as an altered product of muscovite and feldspar in weathering and hydrothermal environments; it may be a component of sericite. It is common in sediments, soils, and argillaceous sedimentary rocks as well as in some low grade metamorphic rocks. The iron-rich member of the illite group, glauconite, in sediments can be differentiated by x-ray analysis.
Celsian is an uncommon feldspar mineral, barium aluminosilicate, BaAl2Si2O8. The mineral occurs in contact metamorphic rocks with significant barium content. Its crystal system is monoclinic, and it is white, yellow, or transparent in appearance. In pure form, it is transparent. Synthetic barium aluminosilicate is used as a ceramic in dental fillings and other applications.
Boussingaultite is a rare ammonium magnesium hydrated sulfate mineral of the chemical formula: (NH4)2Mg(SO4)2 · 6 H2O. The formula of boussingaultite is that of Tutton's salts type. It was originally described from geothermal fields in Tuscany, Italy, where it occurs together with its iron analogue mohrite, but is more commonly found on burning coal dumps. The mineral possess monoclinic symmetry and forms clear, often rounded crystals.
Tobermorite is a calcium silicate hydrate mineral with chemical formula: Ca5Si6O16(OH)2·4H2O or Ca5Si6(O,OH)18·5H2O.
Danalite is an iron beryllium silicate sulfide mineral with formula: Fe2+4Be3(SiO4)3S.
Bararite is a natural form of ammonium fluorosilicate (also known as hexafluorosilicate or fluosilicate). It has chemical formula (NH4)2SiF6 and trigonal crystal structure. This mineral was once classified as part of cryptohalite. Bararite is named after the place where it was first described, Barari, India. It is found at the fumaroles of volcanoes (Vesuvius, Italy), over burning coal seams (Barari, India), and in burning piles of anthracite (Pennsylvania, U.S.). It is a sublimation product that forms with cryptohalite, sal ammoniac, and native sulfur.
Chamosite is the Fe2+end member of the chlorite group. A hydrous aluminium silicate of iron, which is produced in an environment of low to moderate grade of metamorphosed iron deposits, as gray or black crystals in oolitic iron ore. Like other chlorites, it is a product of the hydrothermal alteration of pyroxenes, amphiboles and biotite in igneous rock. The composition of chlorite is often related to that of the original igneous mineral so that more Fe-rich chlorites are commonly found as replacements of the Fe-rich ferromagnesian minerals (Deer et al., 1992).
Woodhouseite belongs to the beudantite group AB3(XO4)(SO4)(OH)6 where A = Ba, Ca, Pb or Sr, B = Al or Fe and X = S, As or P. Minerals in this group are isostructural with each other and also with minerals in the crandallite and alunite groups. They crystallise in the rhombohedral system with space group R3m and crystals are usually either tabular {0001} or pseudo-cubic to pseudo-cuboctahedral. Woodhouseite was named after Professor Charles Douglas Woodhouse (1888–1975), an American mineralogist and mineral collector from the University of California, Santa Barbara, US, and one-time General Manager of Champion Sillimanite, Inc.
Rubicline, also referred to as Rb-microcline, is the rubidium analogue of microcline, an important tectosilicate mineral. Its chemical formula is (Rb, K)[AlSi3O8] with an ideal composition of RbAlSi3O8. Chemical analysis by electron microprobe indicated the average weight of the crystal is 56.66% SiO2, 16.95% Al2O3, and 23.77% Rb2O, along with trace amounts of caesium oxide (Cs2O) and iron(III) oxide (Fe2O3).
Carlin–type gold deposits are sediment-hosted disseminated gold deposits. These deposits are characterized by invisible gold in arsenic rich pyrite and arsenopyrite. This dissolved kind of gold is called "Invisible Gold", as it can only be found through chemical analysis. The deposit is named after the Carlin mine, the first large deposit of this type discovered in the Carlin Trend, Nevada.
Wairakite is a zeolite mineral with an analcime structure but containing a calcium ion. The chemical composition is Ca8(Al16Si32O96)•16H2O. It is named for the location of its discovery in Wairakei, North Island, New Zealand, by Alfred Steiner in 1955. The first finds were in hydrothermally altered rhyolitic tuffs, ignimbrites and volcaniclastic rocks. The mineral has since been found in metamorphic rocks and in geothermal areas. It was most likely first successfully synthesized in a laboratory in 1970.
Bicchulite has an ideal chemical formula of 2CaO •Al2O3 •SiO2 •H2O, which was formularized from the hydrothermal synthesis of synthetic gehlenite (2CaO •Al2O3 •SiO2). Also, bicchulite was sighted in the mines of Japan with related minerals. This sodalite-type structured bicchulite has an uncommon ratio of aluminium to silicon, causing difficulties deciphering the structure. Because of bicchulite's structure it has a powdery texture, which leads to complications in obtaining information on the mineral's physical properties. Despite this problem, the color, specific gravity, and crystal size of bicchulite are known. Although bicchulite was only discovered about 40 years ago, technology has been rapidly advancing, allowing more accurate results to be made from experiments done today.
Wattersite is a rare mercury chromate mineral with the formula Hg+14Hg+2Cr+6O6. It occurs in association with native mercury and cinnabar in a hydrothermally altered serpentinite. It was first described from Clear Creek claim, San Benito County, California, USA in 1961. It was named to honor Californian mineral collector Lucius "Lu" Watters.
Lucabindiite is a mineral discovered in 1998 from the La Fossa crater at Vulcano, the Aeolian islands off the coast of Italy. It has the chemical formula As4O6(Cl,Br) and is hexagonal. After months of collecting sublimates and encrustations, the researchers discovered lucabindiite which was found on the surface of pyroclastic breccia. The mineral is named after Luca Bindi, who was a professor of mineralogy and former head of the Division of Mineralogy of the Natural History Museum of the University of Florence.
Antigorite is a lamellated, monoclinic mineral in the phylosilicate serpentine subgroup with the ideal chemical formula of (Mg,Fe2+)3Si2O5(OH)4. It is the high-pressure polymorph of serpentine and is commonly found in metamorphosed serpentinites. Antigorite, and its serpentine polymorphs, play an important role in subduction zone dynamics due to their relative weakness and high weight percent of water (up to 13 weight % H2O). It is named after its type locality, the Geisspfad serpentinite, Valle Antigorio in the border region of Italy/Switzerland and is commonly used as a gemstone in jewelry and carvings.
Fumarole minerals are minerals which are deposited by fumarole exhalations. They form when gases and compounds desublimate or precipitate out of condensates, forming mineral deposits. They are mostly associated with volcanoes following deposition from volcanic gas during an eruption or discharge from a volcanic vent or fumarole, but have been encountered on burning coal deposits as well. They can be black or multicoloured and are often unstable upon exposure to the atmosphere.
References
- ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID 235729616.
- ↑ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Buddingtonite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 14 March 2022.
- ↑ Buddingtonite, Mindat.org , retrieved 13 June 2022
- ↑ Webmineral data
- ↑ Mookherjee, M.; Redfern, S. A. T.; Swainson, I.; Harlov, D. E. (December 2004). "Low-temperature behaviour of ammonium ion in buddingtonite [N(D/H)4AlSi3O8] from neutron powder diffraction". Physics and Chemistry of Minerals. 31 (9): 643–649. Bibcode:2004PCM....31..643M. doi:10.1007/s00269-004-0425-8. hdl: 2027.42/46909 . S2CID 47007808.
- ↑ Erd RC, White DE, Fahey JJ, Lee DE (1964). "Buddingtonite, an ammonium feldspar with zeolitic water". American Mineralogist. 49 (7–8): 831–50.
- ↑ Felzer B, Hauff P, Goetz AFH (1994). "Quantitative reflectance spectroscopy of buddingtonite from the Cuprite mining district, Nevada". Journal of Geophysical Research. 99 (B2): 2887–95. Bibcode:1994JGR....99.2887F. doi:10.1029/93JB02975.
- ↑ Yang K, Browne PRL, Huntington JF, Walshe JL (2001). "Characterizing the hydrothermal alteration of the Broadlands-Ohaaki geothermal system, New Zealand, using short-wave infrared spectroscopy". Journal of Volcanology and Geothermal Research. 106 (1–2): 53–65. Bibcode:2001JVGR..106...53Y. doi:10.1016/S0377-0273(00)00264-X.
- ↑ Gulbrandsen RA (1974). "Buddingtonite, ammonium feldspar, in the Phosphoria Formation, southeastern Idaho". USGS Journal of Research. 2 (6): 693–7.
- ↑ Solomon GC, Rossman GR (1988). "NH4+ in pegmatitic feldspars from the southern Black Hills, South Dakota". American Mineralogist. 73: 818–21.
- ↑ Loughan FC, Roberts FI, Linder AW (1983). "Buddingtonite (NH4-feldspar) in the Condor Oilshale Deposit, Queensland, Australia". Mineralogical Magazine. 47 (344): 327–34. Bibcode:1983MinM...47..327L. doi:10.1180/minmag.1983.047.344.07. S2CID 140724010.
