Bobfergusonite

{{Short description|Mineral}} {{Infobox mineral | name = Bobfergusonite | category = Phosphate mineral | image = | caption = | formula = Na₂Mn₅FeAl(PO₄)₆ | IMAsymbol=Bfg<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.AC.15 | dana = 38.2.4.5 | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''P2''₁/n<ref name=Webmin>{{cite web|title=Bobfergusonite|url=http://www.webmineral.com/data/Bobfergusonite.shtml|publisher=Webmineral|accessdate=June 11, 2012}}</ref> | unit cell = a = 12.773&nbsp;Å, <br/>b = 12.486&nbsp;Å,<br>c = 11.038&nbsp;Å; <br/>β = 114.35(13)°; Z&nbsp;=&nbsp;4 | color = Green-brown to red-brown | habit = | twinning = | cleavage = Perfect on {010}<br>Parting on {100}<ref name=handbook>{{cite web|title=Bobfergusonite|url=http://www.handbookofmineralogy.com/pdfs/bobfergusonite.pdf|work=Handbook of Mineralogy|publisher=Mineral Data Publishing|accessdate=June 8, 2012|archive-date=July 16, 2012|archive-url=https://web.archive.org/web/20120716020047/http://www.handbookofmineralogy.com/pdfs/bobfergusonite.pdf|url-status=dead}}</ref> | fracture = Irregular/Uneven | tenacity = Brittle | mohs = 4 | luster = Sub-vitreous, resinous, greasy | polish = | refractive = n_α = 1.694(1) n_β = 1.698(1) n_γ = 1.715(2) | opticalprop = Biaxial (+) | birefringence = δ = 0.021 | 2V = 46° | dispersion = Relatively strong | pleochroism = Visible: X=Y= yellow-orange Z= orange | fluorescence= Not fluorescent | absorption = | streak = Yellow-brown | gravity = | density = 3.54 g/cm³ | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Translucent<ref name=mindat/> to transparent<ref name=handbook/> | other = | references = <ref name=mindat>{{cite web|title=Bobfergusonite|url=http://www.mindat.org/min-700.html|publisher=Mindat|accessdate=June 8, 2012}}</ref> }}

'''Bobfergusonite''' is a mineral with formula Na₂Mn₅FeAl(PO₄)₆. The mineral varies in color from green-brown to red-brown. It was discovered in 1986 in Manitoba, Canada, and named for Robert Bury Ferguson (1920{{ndash}}2015), a professor of geological sciences at the University of Manitoba.<ref>{{cite web |title=Mourning Robert Bury Ferguson, Professor Emeritus |url=https://news.umanitoba.ca/mourning-robert-bury-ferguson-professor-emeritus/ |website=news.umanitoba.ca |language=en}}</ref> {{As of|2012}}, the mineral has only been found in Canada and Argentina.

==Description== Bobfergusonite occurs as equant anhedral single crystals up to {{convert|1|cm|in|abbr=on}} in size or as nodular aggregates of few crystals.<ref name=handbook/><ref name=E600>Ercit, p. 600.</ref> The mineral varies in color from green-brown to red-brown.<ref name=handbook/> Thin fragments of bobfergusonite are transparent.<ref>{{cite journal|last=Roberts|first=Andrew C.|title=New Mineral Names|journal=American Mineralogist|year=1988|volume=73|pages=189–199|url=http://www.minsocam.org/ammin/AM73/AM73_189.pdf}}</ref> Bobfergusonite has been found in association with alluaudite, apatite, beusite, fillowite, and triplite.<ref name=handbook/>

Bobfergusonite is a primary mineral that occurs in the intermediate zone of manganese and fluorine enriched granitic pegmatites.<ref name=mindat/>

==Structure== Bobfergusonite has a layered crystal structure topologically identical to that of alluaudite and wyllieite but with differences in the ordering of metal cations. The two types of layer alternate along ''Y''. One layer consists of chains of metal cation octahedra cross-linked by phosphate tetrahedra. Within the chains metal cations are ordered M³⁺–M²⁺ in a similar fashion to wyllieite. However, the structure of bobfergusonite is distinct by the presence of Al and Fe³⁺ ordering between chains.<ref name=E605/>

The other layer, identical to its wyllieite counterpart, consists of chains running parallel to ''X'': one consisting of alternating, face-sharing sodium and manganese polyhedra and the other edge-sharing sodium polyhedra. These chains are not cross-linked but bind the other layers together.<ref name=E605>Ercit, p. 605.</ref>

==History== Alan J. Anderson discovered large brown crystals in a granitic pegmatite at Cross Lake in Manitoba. Study by electron microprobe and X-ray diffraction identified it as a new mineral related to the wyllieite and alluaudite groups.<ref name=E599/>

The mineral was named for professor Robert Bury Ferguson to celebrate his 65th birthday and retirement from the University of Manitoba.<ref name=E599>Ercit, p. 599.</ref><ref>{{cite journal|last=Hawthorne|first=Frank C.|title=Special Issue Dedicated to Robert Bury Ferguson|journal=Canadian Mineralogist|date=December 1986|volume=24|pages=597–598|url=http://rruff.geo.arizona.edu/doclib/cm/vol24/CM24_597.pdf|publisher=Mineralogical Association of Canada}}</ref> The mineral and the name bobfergusonite were approved by the IMA Commission on New Minerals and Mineral Names.<ref name=E599/>

==Distribution== {{As of|2012}}, bobfergusonite is known from the Nancy pegmatite in Argentina and the Gottcha Claim in Manitoba, Canada.<ref name=mindat/> The type material is held at the University of Manitoba and the Royal Ontario Museum in Toronto.<ref name=handbook/>

==References== {{Reflist}}

===Bibliography=== *{{cite journal|last1=Ercit|first1=T. Scott|last2=Anderson|first2=Alan J.|last3=Černý|first3=Petr|last4=Hawthorne|first4=Frank C.|title=Bobfergusonite: A New Primary Phosphate Mineral from Cross Lake, Manitoba|journal=Canadian Mineralogist|year=1986|volume=24|pages=599–604|url=http://rruff.geo.arizona.edu/doclib/cm/vol24/CM24_599.pdf|publisher=Mineralogical Association of Canada}} *{{cite journal|last1=Ercit|first1=T. Scott|last2=Hawthorne|first2=Frank C.|last3=Černý|first3=Petr|title=The Crystal Structure of Bobfergusonite|journal=Canadian Mineralogist|year=1986|volume=24|pages=605–614|url=http://rruff.geo.arizona.edu/doclib/cm/vol24/CM24_605.pdf|publisher=Mineralogical Association of Canada}}

==Further reading== *{{cite journal|last1=Tait|first1=Kimberly T.|last2=Hawthorne|first2=Frank C.|last3=Černý|first3=Petr|title=Bobfergusonite from the Nancy Pegmatite, San Luis Range, Argentina: Crystal-Structure Refinement and Chemical Composition|journal=Canadian Mineralogist|year=2004|volume=42|issue=3|pages=705–716|url=http://www.geo.arizona.edu/~ktait/cm42_705.pdf|publisher=Mineralogical Association of Canada|doi=10.2113/gscanmin.42.3.705|bibcode=2004CaMin..42..705T }}

==External links== * [http://www.mindat.org/gallery.php?min=700 Images of bobfergusonite] from mindat.org

Category:Monoclinic minerals Category:Minerals in space group 14 Category:Sodium minerals Category:Manganese(II) minerals Category:Iron(III) minerals Category:Aluminium minerals Category:Phosphate minerals