# Minyulite

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{{Short description|Phosphate mineral}}
{{Infobox mineral
| name        = Minyulite
| category    = [Phosphate mineral](/source/Phosphate_mineral)
| boxwidth    = 
| boxbgcolor  = 
| image       = Minyulite-101599.jpg
| imagesize   = 260px
| caption     = Colorless minyulite crystals from Tom's Phosphate quarry, Kapunda, Mount Lofty Ranges, South Australia (Field of view 4 mm)
| formula     = KAl<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>F·4(H<sub>2</sub>O)
| IMAsymbol   = Myu<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   = 372.57 g/mol
| strunz      = 8.DH.05
| system      = [Orthorhombic](/source/Orthorhombic)
| class       = Pyramidal (mm2) <br/><small>(same [H-M symbol](/source/H-M_symbol))</small>
| symmetry    = ''Pba2''
| unit cell   = a = 9.34&nbsp;Å, b = 9.74&nbsp;Å, <br/>c = 5.52&nbsp;Å; Z&nbsp;=&nbsp;2
| color       = Colorless to white, greenish yellow
| habit       = Radiating fibrous to prismatic crystals
| twinning    = 
| cleavage    = {001} Perfect
| fracture    = Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern. 
| tenacity    = Brittle
| mohs        = 3.5
| luster      = Vitreous, silky in aggregates
| refractive  = n<sub>α</sub> = 1.531 n<sub>β</sub> = 1.534 n<sub>γ</sub> = 1.538
| opticalprop = Biaxial (+)
| birefringence = δ = 0.007
| pleochroism = 
| 2V          =	Measured: 70°, calculated: 82°
| streak      = White
| gravity     = 2.45
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| diaphaneity = Transparent
| other       = 
| references  = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Minyulite Mineralienatlas]</ref><ref name=Mindat>[http://www.mindat.org/min-2724.html Minyulite at Mindat]</ref><ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/minyulite.pdf Handbook of Mineralogy]</ref><ref name=Webmin>[http://www.webmineral.com/data/Minyulite.shtml Webmineral data]</ref><ref name=CNMNC>CNMNC Newsletter 63; Mineralogical Magazine, 85, https://doi.org/10.1180/mgm.2021.74</ref>
}}

'''Minyulite''' is a rare [phosphate mineral](/source/phosphate_mineral) with a [chemical formula](/source/chemical_formula) of {{chem2|KAl2(PO4)2F*4(H2O)}} (redefinition, IMA21-E).<ref name=CNMNC/>

It occurs as groups of radiating fine fibrous crystals within rock cracks of phosphatic [ironstone](/source/ironstone). Minyulite belongs to the orthorhombic [crystal system](/source/crystal_system). This indicates that it has three axes of unequal length yet all are perpendicular to each other. Its cell constants are a=9.35, b=9.74 c=5.52.<ref>Kampf, A.R. (1977) Minyulite: its atomic arrangement. American Mineralogist, 62, 256–262.</ref>

As for its optical properties, Minyulite is an [anisotropic](/source/anisotropic) mineral which means the velocity of light differs when traveling through it depending on the cut of its cross-section which gives it more than one refractive index.<ref name=Klein>Klein, C., and Dutrow, B.(2007) The 23rd Edition of the Manual of Mineral Science, 290 p. John Wiley and Sons, Inc. Hoboken, New Jersey, U.S.A.</ref>  The mineral is optically biaxial. Its [birefringence](/source/birefringence) value is 0.007.<ref>Spencer, L.J., F.A. Bannister, M.H. Hey, and H. Bennett (1943) Minyulite (hydrous K-Al fluophosphate) from South Australia. Mineralogical Magazine, 26, 309–314.</ref> It has three [refractive indices](/source/refractive_indices) which are nα=1.531 nβ=1.534 nγ=1.538.<ref>Simpson, E.S., and Le Mesurier, C.R.(1933)Minyulite: a new phosphate mineral from Dandaragn. Journal of the Royal Society of Western Australia: 19-13.</ref>  Refractive indices are a ratio of the speed of light in a median with respect to the speed of light passing through the mineral.<ref name=Klein/>

==Occurrence==
[[File:Minyulite-Sincosite-mrz312b.jpg|thumb|left|Minyulite (white) and [sincosite](/source/sincosite) (green), from Ross Hannibal Mine, [Lead District](/source/Lead%2C_South_Dakota), [South Dakota](/source/South_Dakota), US (size: 7.1 x 5.4 x 2.7 cm)]]
It was first described in 1933 for an occurrence in Western Australia and named after the [type locality](/source/Type_locality_(geology)), [Minyulo Well](/source/Minyulo_Well) in [Western Australia](/source/Western_Australia).<ref name=Mindat/>

Minyulite is considered as a secondary phosphate since it is formed by the alteration of a primary phosphate. It occurs in association with [dufrenite](/source/dufrenite), [apatite](/source/apatite), [fluellite](/source/fluellite), [wavellite](/source/wavellite), [variscite](/source/variscite) and [leucophosphite](/source/leucophosphite).<ref name=HBM/>

The mineral can be found in the underlying phosphatized rock zone of ornithogenic soil. Minyulite is not found in abundance, it can be found in the seashore of the maritime Arctic.<ref>Tatur, A., and Keck, A. (1990) Phosphates in ornithogenic soils of the Maritime Antarctic.Proc. NIPR Symp. Polar Biol: 3, 133-150.</ref>
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==References==
{{Reflist}}

{{Commons category}}

Category:Phosphate minerals
Category:Orthorhombic minerals
Category:Minerals in space group 32
Category:Potassium minerals
Category:Aluminium minerals

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Adapted from the Wikipedia article [Minyulite](https://en.wikipedia.org/wiki/Minyulite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Minyulite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.