# Bultfonteinite

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{{Short description|Nesosilicate mineral}}
{{infobox mineral
| name        = Bultfonteinite
| category    = [Nesosilicates](/source/Nesosilicates)
| image       = Bultfonteinite - Linxi, Chifeng City, Inner Mongolia, China.jpg
| imagesize   = 260px
| caption     = Bultfonteinite from Shijiangshan mine, China
| formula     = Ca<sub>2</sub>SiO<sub>2</sub>(OH,F)<sub>4</sub>
| IMAsymbol=Bul<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      = 9.AG.80<ref name=mindat/>
| dana        = 52.4.7.2<ref name=mindat/>
| system      = [Triclinic](/source/Triclinic)
| class       = Pinacoidal ({{overbar|1}})<br/><small>(same [H-M symbol](/source/H-M_symbol))</small>
| symmetry    = ''P''{{overbar|1}}
| unit cell   = a = 10.99&nbsp;Å, b = 8.18&nbsp;Å<br/>c = 5.67&nbsp;Å, α = 93.95°<br/>β = 91.32°, γ = 89.85°;<ref name=mindat/> Z&nbsp;=&nbsp;4
| color       = Colorless, pink, light brown
| habit       = 
| twinning    = Interpenetrating on {100} and {010}; polysynthetic
| cleavage    = Good on {100} and {010}
| fracture    = [Conchoidal](/source/Conchoidal_fracture)
| tenacity    = 
| mohs        = 4.5
| luster      = Vitreous
| polish      = 
| refractive  = n<sub>α</sub> = 1.587<br>n<sub>β</sub> = 1.590<br>n<sub>γ</sub> = 1.597<ref name=mindat/>
| opticalprop = Biaxial (+)
| birefringence = δ = 0.010<ref name=mindat/>
| 2V          = 70° (measured)
| dispersion  = r > v; barely perceptible
| pleochroism = 
| fluorescence= 
| absorption  =
| streak      = White<ref name=mindat>{{cite web |title=Bultfonteinite |url=http://www.mindat.org/min-800.html |publisher=Mindat |access-date=July 19, 2012 |archive-date=November 14, 2009 |archive-url=https://web.archive.org/web/20091114021049/http://www.mindat.org/min-800.html |url-status=live }}</ref>
| gravity     = 
| density     = 
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = Soluble in [hydrochloric acid](/source/hydrochloric_acid)<ref name=newNames>{{cite journal |last=Foshag |first=W. F. |title=New Mineral Names: Bulfonteinite |journal=American Mineralogist |date=January 1933 |volume=18 |issue=1 |url=http://www.minsocam.org/ammin/AM18/AM18_31.pdf |page=32 |publisher=Mineralogical Society of America |access-date=2012-07-19 |archive-date=2012-07-23 |archive-url=https://web.archive.org/web/20120723012852/http://www.minsocam.org/ammin/AM18/AM18_31.pdf |url-status=live }}</ref>
| diaphaneity = Transparent
| references  =<ref name=handbook>{{cite web |title=Bultfonteinite |url=http://www.handbookofmineralogy.org/pdfs/bultfonteinite.pdf |work=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=July 19, 2012 |archive-date=August 1, 2012 |archive-url=https://web.archive.org/web/20120801114800/http://www.handbookofmineralogy.org/pdfs/bultfonteinite.pdf |url-status=live }}</ref>
}}

'''Bultfonteinite''', originally '''dutoitspanite''', is a pink, light-brown or colorless mineral with [chemical formula](/source/chemical_formula) Ca<sub>2</sub>SiO<sub>2</sub>(OH,F)<sub>4</sub>. It was discovered in 1903 or 1904 in the Bultfontein mine in South Africa, for which the mineral is named, and described in 1932.

==Description==
thumb|left|Acicular crystals from the Wessels Mine in South Africa

Bultfonteinite is transparent and ranges from pale pink or light brown to colorless.<ref>{{cite book |url=https://books.google.com/books?id=Xp9nEAAAQBAJ&pg=PA175 |page=175 |title=Minerals & Gemstones of Southern Africa |first=Bruce |last=Cairncross |publisher=Penguin Random House South Africa |year=2022 |isbn=978-1-77584-754-0 }}</ref> The mineral occurs as radiating prismatic [acicular](/source/Acicular_(crystal_habit)) crystals and radial spherules up to {{cvt|2|cm|in|1}}.<ref name=handbook/>

==Structure==
The [crystal structure](/source/crystal_structure) of bultfonteinite consists of strips of [Ca<sub>4</sub>Si<sub>2</sub>O<sub>4</sub>]<sup>8+</sup>, that run along the 5.67 [Å](/source/angstrom) ''c''-axis, held together by Ca–O–Ca, Ca–F–Ca, Ca–H<sub>2</sub>O–Ca, and Ca–O–Si bonds. Silicon atoms occur in isolated [tetrahedra](/source/tetrahedra) and the calcium atoms have seven-fold [coordination](/source/Coordination_number), derived from a [triangular prism](/source/triangular_prism) with a seventh atom present on one of the square faces.{{sfn|McIver|1963|p=551}}

==History==
In either 1903 or 1904, a miner discovered the first specimen of bultfonteinite on the 480-foot level of the Bultfontein mine in [Kimberley](/source/Kimberley%2C_Northern_Cape), South Africa. The mineral occurred in a several-hundred-foot-tall [horse](/source/Horse_(geology)) of [kimberlite](/source/kimberlite)-enclosed [dolerite](/source/dolerite) and shale fragments. The specimen, mistakenly thought to be [natrolite](/source/natrolite), was given to Alpheus F. Williams. Several years later, additional samples were found by C. E. Adams in the nearby Dutoitspan mine and given to the MacGregor Museum in Kimberley.{{sfn|Parry|Williams|Wright|1932|p=145}} Shortly before 1932, the mineral was found about {{convert|100|mi|km}} to the southeast of Kimberley at the [Jagersfontein Mine](/source/Jagersfontein_Mine) in [Orange River Colony](/source/Orange_River_Colony).{{sfn|Parry|Williams|Wright|1932|p=145}}{{sfn|Murdoch|1955|p=900}}

After John Parry and F. E. Wright described the mineral [afwillite](/source/afwillite) in 1925, Williams recognized that his samples of bultfonteinite were not natrolite, but were likely a new mineral species. Chemical analysis by John Parry and crystallographic and optical determination by Wright proved it to be a new mineral.{{sfn|Parry|Williams|Wright|1932|p=146}} The mineral was described by Parry, Williams, and Wright in 1932 and named ''bultfonteinite''.{{sfn|Parry|Williams|Wright|1932|p=145}} Their original description does not explicitly state the origin of the name, but it is presumably named after the mine in which it was discovered.<ref name=newNames/> Earlier that year in his book ''The Genesis of the Diamond'', Williams had called the mineral dutoitspanite, a name which was "apparently discarded".{{sfn|Murdoch|1955|p=900}}{{sfn|Mountain|1957|p=610}} When the [International Mineralogical Association](/source/International_Mineralogical_Association) was founded, bultfonteinite was [grandfathered](/source/Grandfather_clause) as a valid mineral species.<ref name=mindat/>

The [type material](/source/Type_material_(mineralogy)) is held in England at [Cambridge University](/source/Cambridge_University) and the [Natural History Museum](/source/Natural_History_Museum%2C_London) in London.<ref name=handbook/>

==Occurrence==
Bultfonteinite has been found in Australia, Botswana, Canada, Israel, Japan, Jordan, Russia, South Africa, and the United States.<ref name=mindat/> The mineral was first located outside South Africa in the US state of California in 1955.{{sfn|Murdoch|1955|p=900}} Bultfonteinite has been found in association with [afwillite](/source/afwillite), [apophyllite](/source/apophyllite), [calcite](/source/calcite), [natrolite](/source/natrolite), [oyelite](/source/oyelite), [scawtite](/source/scawtite), and [xonotlite](/source/xonotlite).<ref name=handbook/>

At the [type locality](/source/type_locality_(geology)), the mineral occurred in a large structure of [dolerite](/source/dolerite) and shale fragments in a [kimberlite](/source/kimberlite) pipe.{{sfn|Parry|Williams|Wright|1932|p=145}} In [Crestmore, California](/source/Crestmore_Heights%2C_California), bultfonteinite formed in the contact zone of thermally metamorphosed [limestone](/source/limestone).<ref name=handbook/>

==References==
{{Reflist}}

'''Bibliography'''
* {{Cite journal |last=McIver |first=E. J. |title=The structure of bultfonteinite, Ca<sub>4</sub>Si<sub>2</sub>O<sub>10</sub>F<sub>2</sub>H<sub>6</sub> |journal=[Acta Crystallographica](/source/Acta_Crystallographica) |year=1963 |volume=16 |issue=6 |pages=551–558 |doi=10.1107/S0365110X63001456 |url=http://journals.iucr.org/q/issues/1963/06/00/a03852/a03852.pdf |doi-access=free |bibcode=1963AcCry..16..551M |url-access=subscription}}
* {{Cite journal |last=Mountain |first=E. D. |title=Rhodesite, a new mineral from the Bultfontein mine, Kimberley |journal=[Mineralogical Magazine](/source/Mineralogical_Magazine) |date=December 1957 |volume=31 |issue=239 |pages=607–610 |url=http://www.minersoc.org/pages/Archive-MM/Volume_31/31-239-607.pdf |archive-url=https://web.archive.org/web/20170809233105/http://www.minersoc.org/pages/Archive-MM/Volume_31/31-239-607.pdf |archive-date=2017-08-09 |doi=10.1180/minmag.1957.31.239.01 |bibcode=1957MinM...31..607M}}
* {{Cite journal |last=Murdoch |first=Joseph |title=Bultfonteinite from Crestmore, California |journal=[American Mineralogist](/source/American_Mineralogist) |date=September–October 1955 |volume=40 |issue=9 & 10 |pages=900–904 |url=http://www.minsocam.org/ammin/AM40/AM40_900.pdf |publisher=[Mineralogical Society of America](/source/Mineralogical_Society_of_America)}}
* {{Cite journal |last1=Parry |first1=John |last2=Williams |first2=Alpiieus F. |last3=Wright |first3=F. E. |title=On bultfonteinite, a new fluorine-bearing hydrouscalcium silicate from South Africa. |journal=[Mineralogical Magazine](/source/Mineralogical_Magazine) |date=September 1932 |volume=23 |issue=138 |pages=145–162 |doi=10.1180/minmag.1932.023.138.01 |bibcode=1932MinM...23..145P |url=https://www.minersoc.org/pages/Archive-MM/Volume_23/23-138-145.pdf |archive-url=https://web.archive.org/web/20170815113957/https://www.minersoc.org/pages/Archive-MM/Volume_23/23-138-145.pdf |archive-date=2017-08-15}}

==External links==
* {{Commonscat-inline|Bultfonteinite}}

Category:Calcium minerals
Category:Crestmore Heights, California
Category:Fluorine minerals
Category:Minerals in space group 2
Category:Nesosilicates
Category:Triclinic minerals

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