{{Short description|Hydrated iron phosphate mineral}} {{Infobox mineral |boxbgcolor=#8a8f82| name = Metavivianite | boxtextcolor = #fff | category = Phosphate mineral | image = Metavivianite Pavel-Kartashov.jpg | caption = A 6x4 cm specimen of paramorphosed olive-green to green Metavivianite after oxidized vivianite. From Kerchenskoe deposit, Crimea Oblast, Ukraine. Photo and collection specimen by Pavel Kartashov. | formula = {{Chem|Fe|2+|Fe|3+|2|(PO|4|)|2|(O|H)|2|·6H|2|O}} | IMAsymbol = Mviv<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 = 499.548 g/mol | strunz = 8.DC.25 (10 ed)<br /><small>7/C.14-20 (8 ed)</small> | dana = 40.11.9.4 | system = Triclinic | class = Pinacoidal (1) | symmetry = ''P1bar'' | unit cell = a = 7.989(1)&nbsp;Å, b = 9.321(2)&nbsp;Å <br/>c = 4.629(1)&nbsp;Å; α = 97.34(1)°; β = 95.96(1)°; γ = 108.59(2)° | color = Dark blue to blue-black; Dark green to green-black | habit = Bladed crystals, often with irregular acute multiple terminations. | twinning = {110} | cleavage = Perfect on {110} | tenacity = Sectile | mohs = 1.5–2 | luster = Sub-vitreous, Resinous, Greasy, Dull | streak = Blue or greenish blue | diaphaneity = translucent | gravity = 2.69 | density = | polish = | opticalprop = Biaxial (+) | refractive = n<sub>α</sub> = 1.600 – 3.000, n<sub>β</sub> = 1.640 – 3.000, n<sub>γ</sub> = 1.685 – 3.000<ref name=Handbook/> | birefringence = δ = 0.050 – 0.085 | pleochroism = Visible; X = blue to blue-green; Y,Z = yellow-green | 2V = Measured: 85° (5), Calculated: 90° | dispersion = Very weak | extinction = | length fast/slow = | fluorescence= Not fluorescent | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = <ref name=Handbook /><ref name=Mindat /><ref name=WebMin /> }}

'''Metavivianite''' ({{Chem|Fe|2+|Fe|3+|2|(PO|4|)|2|(O|H)|2|·6H|2|O}}) is a hydrated iron phosphate mineral found in a number of geological environments. As a secondary mineral it is typically formed from oxidizing vivianite.<ref name=Handbook /> Metavivianite is typically found as dark blue or dark green prismatic to flattened crystals.

It was named by C. Ritz, Eric J. Essene, and Donald R. Peacor in 1974 for its structural relationship to vivianite.<ref name=Mindat />

==See also== *List of minerals

==References== {{Reflist|refs= <ref name=Handbook>{{Cite journal |title = Handbook of Mineralogy |url = http://www.handbookofmineralogy.org/pdfs/metavivianite.pdf |author1=John W. Anthony |author2=Richard A. Bideaux |author3=Kenneth W. Bladh |author4=Monte C. Nichols |name-list-style=amp |year = 2005 |publisher = Mineral Data Publishing }}</ref> <ref name=Mindat>[https://www.mindat.org/min-2695.html Metavivianite] (Mindat.org)</ref> <ref name=WebMin>[http://webmineral.com/data/Metavivianite.shtml Metavivianite Webmineral Data]</ref> }}

Category:Phosphate minerals Category:Hexahydrate minerals Category:Iron(III) minerals Category:Triclinic minerals Category:Minerals in space group 1 Category:Minerals described in 1974

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