{{Infobox mineral | name = Allactite | category = Arsenate mineral | image = Allactite-319883.jpg | imagesize = 260px | alt = | caption = Picture width 3 mm | formula = Mn<sub>7</sub>(AsO<sub>4</sub>)<sub>2</sub>(OH)<sub>8</sub> |IMAsymbol=Ala<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 = 8.BE.30 | dana = 41.2.1.1 | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''P''2<sub>1</sub>/a | unit cell = a = 11.03, b = 12.12 <br/>c = 5.51 [Å], β = 114°, Z = 2 | color = Brown, dark to light purplish red, brownish red, colorless to white | habit = Elongated prisms, bladed, tabular, rosette-like aggregates | twinning = | cleavage = Distinct, {001} | fracture = Uneven | tenacity = Brittle | mohs = 4.5 | luster = Vitreous, slightly greasy on fracture surfaces | refractive = n<sub>α</sub> = 1.755–1.761<br/> n<sub>β</sub> = 1.772–1.786<br/> n<sub>γ</sub> = 1.774–1.787 | opticalprop = Biaxial (−) | birefringence = | 2V = ~0° | pleochroism = X = blood-red; Y = pale yellow; Z = sea-green | streak = Gray to faint brown | gravity = 3.83 (meas.), 3.94 (calc.) | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = | other = | references = <ref>[http://www.mindat.org/min-122.html Allactite]. Mindat</ref><ref name=hand>[http://www.handbookofmineralogy.org/pdfs/allactite.pdf Allactite]. Handbook of Mineralogy</ref><ref>{{cite journal|author=Moore P. |year=1968|title= Crystal chemistry of the basic manganese arsenate minerals: II. The crystal structure of allactite|journal= American Mineralogist|volume= 53|pages= 733–741|url=http://www.minsocam.org/ammin/AM53/AM53_733.pdf}}</ref> }} '''Allactite''' is a rare arsenate mineral of metamorphosed manganese zinc ore deposits. It is found in Sweden and New Jersey, US. Its name originated from the Greek αλλάκτειν (allaktein) meaning "to change", referring to the strong pleochroism of the mineral.<ref name=hand/>
==References== {{reflist}}
==Bibliography== *<small>Palache, P.; Berman H.; Frondel, C. (1960). "''Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)"'' John Wiley and Sons, Inc., New York, pp. 785-787.</small>
Category:Arsenate minerals Category:Manganese(II) minerals Category:Hydroxide minerals Category:Monoclinic minerals Category:Minerals in space group 14 Category:Minerals described in 1884
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