{{Short description|Phyllosilicate mineral}} {{infobox mineral | name = Magadiite | image = Magadiite-696064.jpg | alt = | caption = Magadiite. Collected in 1990 from Lake Magadi, Kajiado County, Kenya. | category = Phyllosilicate minerals | formula = NaSi<sub>7</sub>O<sub>13</sub>(OH)<sub>3</sub>·4(H<sub>2</sub>O) | IMAsymbol = Mgd<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = | strunz = 9.EA.20 | dana = | symmetry = ''C2/m'' (no. 12) | unit cell = a = 7.22&nbsp;Å, b = 15.70&nbsp;Å, <br/>c = 6.91&nbsp;Å; β = 97.27°; Z=1 | color = White | colour = | habit = Minute platy crystals; spherulitic aggregates; powdery | system = Monoclinic <br/>Unknown space group | twinning = | cleavage = | fracture = | tenacity = Puttylike | mohs = 2 | luster = Vitreous - dull | streak = White | diaphaneity = Translucent to opaque | gravity = 2.25 calculated | density = | polish = | opticalprop = Biaxial | refractive = n<sub>α</sub> = 1.470 | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = Yellow-white under both long and short wave | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Magadiite Mineralienatlas]</ref><ref name=Handbook/><ref name=Webmineral/><ref name=Mindat>[http://www.mindat.org/min-2530.html Mindat.org]</ref><ref>{{cite journal |last1=Garcés |first1=Juan M. |title=Hypothetical Structures of Magadiite and Sodium Octosilicate and Structural Relationships Between the Layered Alkali Metal Silicates and the Mordenite- and Pentasil-Group Zeolites1 |journal=Clays and Clay Minerals |date=1988 |volume=36 |issue=5 |pages=409–418 |doi=10.1346/CCMN.1988.0360505|bibcode=1988CCM....36..409G |s2cid=56036567 |doi-access=free }}</ref> }} '''Magadiite''' is a hydrous sodium silicate mineral (NaSi<sub>7</sub>O<sub>13</sub>(OH)<sub>3</sub>·4(H<sub>2</sub>O)) which precipitates from alkali brines as an evaporite phase. It forms as soft (Mohs hardness of 2) white powdery monoclinic crystal masses.<ref name=Handbook>[http://www.handbookofmineralogy.org/pdfs/Magadiite.PDF Mineral Handbook]</ref><ref name=Webmineral>[https://www.webmineral.com/data/Magadiite.shtml Webmineral]</ref> The mineral is unstable and decomposes during diagenesis leaving a distinctive variety of chert (Magadi-type chert).<ref name=Encyc>''Encyclopedia of Sediments & Sedimentary Rocks'', Springer, 2003, p. 417, {{ISBN|1-4020-0872-4}}</ref>

The mineral was first described by Hans P. Eugster in 1967 for an occurrence in Lake Magadi, Kenya, and is also found at Olduvai Gorge, Tanzania.<ref name=Webmineral/><ref name=Encyc/> It is also reported from alkalic intrusive syenites as in Mont Saint-Hilaire, Canada.<ref name=Handbook/>

==References== {{Reflist}}

Category:Phyllosilicates Category:Sodium minerals Category:Monoclinic minerals Category:Minerals in space group 12

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