{{Infobox mineral | name = Perhamite | category = Phosphate minerals | boxwidth = | boxbgcolor = | image = Perhamite-181540.jpg | imagesize = | caption = Perhamite (spherical crystals aggregates) and sparkly apatite druse on feldspar. | formula = Ca<sub>3</sub>Al<sub>7</sub>(SiO<sub>4</sub>)<sub>3</sub>(PO<sub>4</sub>)<sub>4</sub>(OH)<sub>3</sub>·16.5(H<sub>2</sub>O) | IMAsymbol = Phm<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> | strunz = 8.DO.20 | dana = 43.5.10.1 | system = Trigonal | class = Hexagonal scalenohedral ({{overline|3}}m) <br/>H-M symbol: ({{overline|3}} 2/m) | symmetry = ''P''{{overline|3}}m1 | unit cell = a = 7.021&nbsp;Å, c = 20.218&nbsp;Å; Z&nbsp;=&nbsp;1 | color = Colourless, white, light brown, orange | habit = Spherulitic masses of platy crystals | cleavage = imperfect/fair | mohs = 5 | luster = Vitreous, sub vitreous, pearly | streak = White | gravity = 2.53 | solubility = Insoluble | references = <ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/perhamite.pdf Handbook of Mineralogy]</ref><ref>[http://webmineral.com/data/Perhamite.shtml Webmineral]</ref><ref name=Mindat>[http://www.mindat.org/min-3160.html Mindat]</ref> }}

'''Perhamite''' is a phosphate mineral with the formula Ca<sub>3</sub>Al<sub>7</sub>(SiO<sub>4</sub>)<sub>3</sub>(PO<sub>4</sub>)<sub>4</sub>(OH)<sub>3</sub>·16.5(H<sub>2</sub>O). It occurs in rare isolated masses in amblygonite-rich pegmatite deposits throughout the world. It was discovered in platy sheed{{clarify|date=May 2013|reason=Not in any dictionary I have access to}} form of 1mm hexagonal crystals.<ref name = mills>Mills,S., Mumme, G., Grey, I. and Bordet, P.(2006): The crystal structure of perhamite. Mineralogical Magazine 70,201–209</ref><ref name = frost>Frost, Ray L., Matt L. Weier, and Stuart J. Mills. (2007)A Vibrational Spectroscopic Study of Perhamite, an Unusual Silico-Phosphate, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy 67.3, 604–10</ref> It was first described in 1977 by P.J. Dunn and D.E. Appleman<ref name = Dunn>Dunn, P. and Appleman, D.: Perhamite, a new calcium aluminum silico-phosphate mineral and a re-examination of viseite. Mineralogical Magazine 41, 437–442</ref> from pegmatite collected from Bell Pit, Newry, Maine. Other specimens have been found in Kapunda, South Australia, in Silver Coin mine near Humboldt County, Nevada<ref name= HBM/> and various locations throughout Europe.<ref name = Mindat/>

==Composition== The formula<ref name = HBM/> Ca<sub>3</sub>Al<sub>7</sub>(SiO<sub>4</sub>)<sub>3</sub>(PO<sub>4</sub>)<sub>4</sub>(OH)<sub>3</sub>·16.5(H<sub>2</sub>O) was determined by measuring its composition with x-ray spectroscopy giving the average amounts of SiO<sub>2</sub> to be 13.72%, Al<sub>2</sub>O<sub>3</sub> to be 27.17%, CaO to be 12.81%, P<sub>2</sub>O<sub>5</sub> to be 21.61%, leaving 24.69% to be determined as H<sub>2</sub>O.<ref name = Mills2>Mills, S. (2003): A note on perhamite from the Moculata( Klemms)phosphate quarry, South Australia, Australia. J. Mineral. 9, 43–45</ref> The formula's essential elements are Al, Ca, H, O, P and Si with trace amounts of Sr. Common impurities of perhamite include Ti, Fe, Mg, Na, and F.<ref name = Mindat/>

==Physical properties== Perhamite can range in color from white to brown and can be translucent to opaque. Its luster is said to be earthy, but vitreous to pearly along fractures. It occurs as radial discoidal, platy hexagonal crystals, in rough spherules up to 1mm thick.<ref name = HBM/> The specific gravity of perhamite is measured at 2.64<ref name = Dunn/> with a calculated density of 2.53. It is structurally related to minerals in the crandallite subgroup, namely Iangreyite.<ref name = iangreyite>Mills, S.J., Kampf, A.R., Sejkora, J., Adams, P.M., Birch, W.D., Plášil, J. (2011): Iangreyite: a new secondary phosphate mineral closely related to perhamite. Mineralogical Magazine, 75, 327–336.</ref>

==Origin of the name== Perhamite is named after Frank Croydon Perham (born 1934), an American geologist and pegmatite miner of West Paris, Maine who is currently part of the faculty of The Maine Pegmatite Workshop and has over 45 years experience in mining pegmatites.<ref>{{Cite web | url=http://pegmatology.uno.edu/Frank_Perham.html |title = Frank Perham}}</ref> Frank Perham died on 31 January 2023.

==See also== *List of minerals

==References== {{Reflist}}

{{commons}}

{{Phosphate minerals}}

Category:Aluminium minerals Category:Phosphate minerals Category:Trigonal minerals Category:Minerals in space group 164