View source for Triploidite

{{Short description|Phosphate mineral}}
{{Infobox mineral
| name        = Triploidite
| boxwidth    =
| boxbgcolor  =
| image       = Triploidite-199681.jpg
| imagesize   = 200px
| alt         =
| caption     = Radial reddish triploidite from the Branchville Quarry, Branchville, [[Fairfield County, Connecticut]], US (7.0 x 4.8 x 2.6 cm)
| category    = [[Phosphate minerals]]
| formula     = {{chem2|(Mn,Fe)2PO4OH}}
| IMAsymbol   = Tpd<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.BB.15
| dana        =
| system      = [[Monoclinic]]
| class       = Prismatic (2/m) <br/><small>(same [[H-M symbol]])</small>
| symmetry    = ''P''2<sub>1</sub>/a
| unit cell   = a = 12.36&nbsp;[[Ångström|Å]], b = 13.27&nbsp;Å <br/>c = 9.94&nbsp;Å; β = 108.23°; Z&nbsp;=&nbsp;16
| color       = Red-brown, light pink, yellow-brown; light pink to light brown in transmitted light.
| colour      =
| habit       = Elongated and striated prismatic crystals; fibrous: columnar to spherulitic
| twinning    =
| cleavage    = On {010}, good; on {120}, fair; on {110}, very poor.
| fracture    = Uneven to subconchoidal
| tenacity    =
| mohs        = {{frac|4|1|2}} – 5
| luster      = Adamantine, vitreous, greasy
| streak      = White, off-white.
| diaphaneity = Transparent, translucent
| gravity     = 3.70 measured
| density     =
| polish      =
| opticalprop = Biaxial (+)
| refractive  = n<sub>α</sub> = 1.725 n<sub>β</sub> = 1.726 n<sub>γ</sub> = 1.730
| birefringence = δ = 0.005
| pleochroism = Weak
| 2V          =
| dispersion  = r > v strong
| extinction  =
| length fast/slow =
| fluorescence =
| absorption  =
| melt        =
| fusibility  =
| diagnostic  =
| solubility  = Soluble in acids.
| impurities  =
| alteration  =
| other       =
| prop1       =
| prop1text   =
| references  = <ref name=Handbook/><ref name=Mindat/><ref name=Webmin/>
}}

'''Triploidite''' is an uncommon [[manganese]] [[iron]] [[phosphate mineral]] with [[Chemical formula|formula]]:  {{chem2|([[Mn]], [[Fe]])2[[PO4]][[Hydroxyl|OH]]}}. It crystallizes in the [[monoclinic]] [[crystal system]] and typically occurs as elongated and striated slender prisms which may be columnar to fibrous. Its crystals may be pinkish to yellowish brown or red-orange.<ref name=Handbook>[http://rruff.geo.arizona.edu/doclib/hom/triploidite.pdf Handbook of Mineralogy]</ref>

It was first described in 1878 for an occurrence in the Branchville Quarry, [[Branchville, Connecticut|Branchville]], Fairfield County, Connecticut. The name is derived from its resemblance to [[triplite]].<ref name=Mindat>[http://www.mindat.org/min-4022.html Mindat]</ref>

It typically occurs as a [[hydrothermal alteration]] product of primary phosphate minerals in [[granite]] [[pegmatite]]s. It occurs with [[triplite]], [[lithiophilite]], [[triphylite]], [[eosphorite]], [[dickinsonite]] and [[rhodochrosite]].<ref name=Handbook/><ref name=Webmin>[http://webmineral.com/data/Triploidite.shtml Webmineral data]</ref>

It forms a [[solid solution]] series with the iron rich [[wolfeite]].<ref name=Mindat/><ref name=Webmin/>

==See also==
{{Portal|Earth sciences}}
* [[Classification of minerals (disambiguation)|Classification of minerals]]
* [[List of minerals]]

==References==
{{commons category| Triploidite}}
{{Reflist}}

{{Manganese minerals}}

[[Category:Manganese(II) minerals]]
[[Category:Iron(II) minerals]]
[[Category:Phosphate minerals]]
[[Category:Monoclinic minerals]]
[[Category:Minerals in space group 14]]


{{Phosphate-mineral-stub}}