{{Short description|Phosphate mineral}} {{Infobox mineral | name = Tarbuttite | category = Phosphate minerals | boxwidth = | boxbgcolor = | image = Tarbuttite.JPG | imagesize = | caption = Tarbuttite from Broken Hill mine (Kabwe mine) in Central Province, Zambia | formula = Zn<sub>2</sub>(PO<sub>4</sub>)(OH) | IMAsymbol = Tbt<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.35 | dana = 41.6.7.1 | system = Triclinic | class = Pinacoidal ({{overbar|1}}) <br/><small>(same H-M symbol)</small> | symmetry = ''P''{{overbar|1}} | unit cell = a = 5.400&nbsp;Å, b = 5.654&nbsp;Å <br/>c = 6.465&nbsp;Å, α = 102.51° <br/>β = 102.46°, γ = 86.50° <br/>Z&nbsp;=&nbsp;2<ref name=handbook/> | color = White, colorless, yellow, red, green, or brown | habit =Equant to short prismatic [001], sheaf-like aggregates, crusts, individual crystals rounded and deeply striated | twinning = | cleavage = Perfect on {010} | fracture = Irregular, uneven | tenacity = | mohs = 3.5 | luster = Vitreous, pearly on cleavages<ref name=handbook>{{cite web|title=Tarbuttite|url=http://www.handbookofmineralogy.com/pdfs/tarbuttite.pdf|work=Handbook of Mineralogy|publisher=Mineral Data Publishing|accessdate=July 13, 2012|archive-date=July 15, 2012|archive-url=https://web.archive.org/web/20120715110930/http://www.handbookofmineralogy.com/pdfs/tarbuttite.pdf|url-status=dead}}</ref> | polish = | refractive = n<sub>α</sub> = 1.660<br>n<sub>β</sub> = 1.705<br>n<sub>γ</sub> = 1.713 | opticalprop = Biaxial (−) | birefringence = δ = 0.053 | 2V = 50° (measured) | dispersion = Weak,<ref name=mindat/> strong<ref name=handbook/> | pleochroism = | fluorescence= Non-fluorescent<ref name=webmin>{{cite web|title=Tarbuttite|url=http://www.webmineral.com/data/Tarbuttite.shtml|publisher=Webmineral|accessdate=July 13, 2012}}</ref> | absorption = | streak = White | gravity = 4.12; 4.19 (calc.) | density = 4.12 g/cm<sup>3</sup> (measured) | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent, translucent | other = | references =<ref name=mindat>{{cite web|title=Tarbuttite|url=http://www.mindat.org/min-3892.html|publisher=Mindat|accessdate=July 13, 2012}}</ref> }}

'''Tarbuttite''' is a rare phosphate mineral with formula Zn<sub>2</sub>(PO<sub>4</sub>)(OH). It was discovered in 1907 in what is now Zambia and named for Percy Coventry Tarbutt.

==Description and habit== Tarbuttite is white, yellow, red, green, brown, or colorless; in transmitted light it is colorless.<ref name=mindat/> Traces of copper cause green coloring, while iron hydroxides cause the other colors. Colorless crystals tend to be transparent while colored specimens have varying degrees of transparency.<ref name=S22/>

The mineral occurs as equant to short prismatic crystals up to {{convert|2|cm|in|abbr=on}}, in sheaf-like or saddle-shaped aggregates, or as crusts.<ref name=handbook/> Individual crystals are commonly rounded and striated.<ref name=mindat/>

==Structure== Zinc ions are surrounded by oxygen in a nearly perfect trigonal bipyramid and phosphate groups are tetrahedral. The crystal structure consists of zig-zag chains of Zn<sub>1</sub> polyhedra linked by phosphate groups and pairs of Zn<sub>2</sub> polyhedra. In each unit cell are two formula units of Zn<sub>2</sub>(PO<sub>4</sub>)(OH).<ref name=C321>Cocco, p. 321.</ref>

==History== Tarbuttite was discovered in 1907 in Broken Hill mine, Northern Rhodesia, (now Kabwe, Zambia).<ref name=mindat/><ref name=S1>Spencer, p. 1.</ref> The mineral was described from specimens in cellular limonite in the largest hill of the group, Kopje No. 2.<ref name=S2>Spencer, p. 2.</ref><ref name=S30/> In a cave discovered in Kopje No. 1 by boring a tunnel,<ref name=S1/> tarbuttite was also found in association with hopeite as obscure crystals and crystals smaller than {{convert|1/16|mm|in|abbr=on}}<ref name=S30>Spencer, p. 30.</ref> and as an encrustation on some bones.<ref name=S31>Spencer, p. 31.</ref> Several specimens of the mineral were collected by Percy Coventry Tarbutt, a director of the Broken Hill Exploration Company.<ref name=S22>Spencer, p. 22.</ref><ref name=S2/> In 1907, the name ''tarbuttite'' was proposed by L.J. Spencer in the journal ''Nature'' in honor of Tarbutt.<ref name=S22/>

When the International Mineralogical Association was founded, tarbuttite was grandfathered as a valid mineral species.<ref name=mindat/>

==Occurrence== Tarbuttite has been found in Algeria, Angola, Australia, Canada, China, Namibia, the United States, and Zambia.<ref name=handbook/><ref name=mindat/>

Tarbuttite forms as secondary mineral in oxidized zinc deposits. It has been found in association with cerussite, descloizite, hemimorphite, hopeite, hydrozincite, "limonite", parahopeite, pyromorphite, scholzite, smithsonite, and vanadinite.<ref name=handbook/>

==See also== *List of minerals named after people

==References== {{Reflist}}

===Bibliography=== *{{cite journal|last1=Cocco|first1=G.|last2=Fanfani|first2=L.|last3=Zanazzi|first3=P. F.|title=The crystal structure of tarbuttite, Zn2(ОH)РО4|journal=Zeitschrift für Kristallographie|year=1966|volume=123|issue=5|pages=321–329|url=http://rruff.info/uploads/ZK123_321.pdf|doi=10.1524/zkri.1966.123.16.321|s2cid=96221726}} *Palache, P.; Berman H.; Frondel, C. (1960). "''Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)"'' John Wiley and Sons, Inc., New York, pp. 869–871. *{{cite journal|last=Spencer|first=L. J.|title=On Hopeite and other zinc phosphates and associated minerals from the Broken Hill mines, North-Western Rhodesia|journal=Mineralogical Magazine|date=April 1908|volume=15|issue=68|pages=1–38|url=http://www.minersoc.org/pages/Archive-MM/Volume_15/15-68-1.pdf|publisher=The Mineralogical Society|doi=10.1180/minmag.1908.015.68.02|bibcode=1908MinM...15....1S|archive-date=2014-01-06|access-date=2012-07-14|archive-url=https://web.archive.org/web/20140106184049/http://www.minersoc.org/pages/Archive-MM/Volume_15/15-68-1.pdf|url-status=dead}}

==Further reading== *{{cite journal|last=Richmond|first=Wallace E.|title=Tarbuttite|journal=American Mineralogist|date=December 1938|volume=23|issue=12|pages=881–893|url=http://www.minsocam.org/ammin/AM23/AM23_881.pdf|publisher= Mineralogical Society of America}}

==External links== {{commonscat-inline|Tarbuttite}}

Category:Triclinic minerals Category:Zinc minerals Category:Phosphate minerals Category:Hydroxide minerals Category:Minerals in space group 2 Category:Minerals described in 1907