# Tsumcorite

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{{Short description|Rare hydrated lead arsenate mineral}}
{{Infobox mineral
| name = Tsumcorite
| category = [Arsenate minerals](/source/Arsenate_minerals)
| boxwidth = 
| boxbgcolor = 
| image = Tsumcorite-160209.jpg
| caption = Tsumcorite from the Tsumeb Mine, Namibia
| formula = PbZnFe<sup>2+</sup>(AsO<sub>4</sub>)<sub>2</sub>.H<sub>2</sub>O
| IMAsymbol   = Tmc<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 = 624.29 g/mol
| strunz = 8.CG.15
| dana = 40.02.09.01
| system = [Monoclinic](/source/Monoclinic)
| class = Prismatic (2/m) <br/><small>(same [H-M symbol](/source/H-M_symbol))</small>
| symmetry  = ''C2/m'' (no. 12)
| unit cell = a = 9.124&nbsp;[Å](/source/%C3%85ngstr%C3%B6m), b = 6.329&nbsp;Å <br/>c = 7.577&nbsp;Å; β = 115.3°; Z&nbsp;=&nbsp;2
| color = Yellow-brown, red-brown, orange
| habit = Radiating, fibrous crusts
| twinning = Common, on an unknown law
| cleavage = Good on {001}
| fracture = 
| tenacity = 
| mohs = {{frac|4|1|2}} 
| luster = Vitreous 
| refractive =  n<sub>α</sub> = 1.87–1.91 n<sub>β</sub> = 1.89–1.93 n<sub>γ</sub> = 1.92–1.96
| opticalprop = Biaxial
| birefringence = 
| pleochroism = Weak, yellow to yellow-green 
| 2V = 67–83.5°
| streak = Yellow 
| gravity = 5.2
| melt = 
| fusibility = 
| diagnostic = 
| solubility = Dissolves in HCl
| diaphaneity = Translucent
| other =  
| references = <ref name=Dana>Gaines et al (1997) Dana’s New Mineralogy Eighth Edition.  Wiley</ref><ref name=Mindat>[http://www.mindat.org/min-4039.html Mindat.org]</ref><ref name=Webmin>[http://www.webmineral.com/data/Tsumcorite.shtml Webmineral data]</ref><ref name=HOM>[http://www.handbookofmineralogy.org Handbook of Mineralogy]</ref><ref name=AM57>Fleischer M (1972) New mineral names, American Mineralogist 57, 1558, being a summary of Geier, Kautz and Muller (1971) Neues Jahrbuch für Mineralogie (Monatshefte) 1971: 304–309</ref><ref>{{cite journal |last1=Tillmanns |first1=E. |last2=Gebert |first2=W. |title=The crystal structure of tsumcorite, a new mineral from the Tsumeb mine, S. W. Africa |journal=Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry |date=1 December 1973 |volume=29 |issue=12 |pages=2789–2794 |doi=10.1107/S0567740873007545|bibcode=1973AcCrB..29.2789T }}</ref>}}
'''Tsumcorite''' is a rare hydrated [lead](/source/lead) [arsenate](/source/arsenate) mineral that was discovered in 1971, and reported by Geier, Kautz and Muller.<ref name = AM57/> It was named after the '''TSUM'''eb '''COR'''poration  mine at [Tsumeb](/source/Tsumeb), in Namibia, in recognition of the Corporation's support for mineralogical investigations of the orebody at its Mineral Research Laboratory.<ref name=HOM/>

== Unit cell ==
Tsumcorite belongs to the [monoclinic crystal class](/source/Monoclinic_crystal_system) 2/m, which means that it has a twofold [axis of symmetry](/source/Rotational_symmetry) along the b [axis](/source/Crystal_structure) and a [mirror plane](/source/Reflection_symmetry) perpendicular to this, in the plane containing the a and c axes.  The a and c axes are inclined to each other at angle β = 115.3°.  The [unit cell](/source/unit_cell) parameters are a = 9.124 Å to 9.131 Å, b = 6.326 Å to 6.329 Å and c = 7.577 Å to 7.583 Å.<ref name=Dana/><ref name = Mindat/><ref name=Webmin/><ref name=AM57/> There are two formula units per unit cell (Z = 2), and the [space group](/source/space_group) is C2/m, meaning that the cell is a [C-face centred lattice](/source/Bravais_lattice), with lattice points in the center of the C face as well as at the corners of the cell.<ref name=Ott>Crystallography (1993) Walter Borchardt-Ott, Springer Verlag</ref> The structure is related to the [brackebushite](/source/brackebushite) group structure.<ref name=Dana/>

== Mineral series ==
Tsumcorite belongs to the helmutwinklerite group,<ref name = Dana/> whose members are
*tsumcorite PbZnFe<sup>2+</sup>(AsO<sub>4</sub>)<sub>2</sub>.H<sub>2</sub>O
*helmutwinklerite PbZn<sub>2</sub>(AsO<sub>4</sub>)<sub>2</sub>.2H<sub>2</sub>O
*thometzekite PbCu<sup>2+</sup><sub>2</sub>(AsO<sub>4</sub>)<sub>2</sub>.2H<sub>2</sub>O
*[mawbyite](/source/mawbyite) PbFe<sup>3+</sup><sub>2</sub>(AsO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>
Tsumcorite forms a series with helmutwinklerite as Zn replaces the Fe<sup>2+</sup>, with thometzekite as Cu replaces the Zn and Fe<sup>2+</sup>,<ref name=Dana/><ref name=Webmin/> and also with mawbyite.<ref name=AJM>Australian Journal of Mineralogy (1997) 3-1:62</ref>

== Crystal habit and properties ==
Crystals are [prismatic](/source/Prism_(geometry)), elongated along the b axis, or wedge-shaped.  They occur in radiating sheaves and spherulites, and as fibrous crusts or earthy and powdery material.<ref name=HOM/>   [Cleavage](/source/Cleavage_(crystal)) is good perpendicular to the c axis,<ref name=HOM/> and [twinning](/source/Twinning_(crystallography)) is common.<ref name=HOM/>

Tsumcorite is yellow-brown, red-brown or orange in color, and it is one of the few minerals that have a yellow [streak](/source/Streak_(mineralogy)) ([orpiment](/source/orpiment) and [crocoite](/source/crocoite) are two others).  It is translucent, with a vitreous [luster](/source/Lustre_(mineralogy)), and [dichroic](/source/dichroic) yellow to yellow-green.<ref name=Dana/><ref name=AM57/> The optical class is biaxial and the [refractive indices](/source/refractive_indices) are approximately equal to 1.90.<ref name=Dana/><ref name=Webmin/><ref name=AM57/>

The mineral is moderately hard, with a [Mohs hardness](/source/Mohs_hardness) of {{frac|4|1|2}}, between [fluorite](/source/fluorite) and [apatite](/source/apatite),<ref name=Dana/><ref name = Mindat/><ref name=Webmin/><ref name=HOM/> and quite heavy, due to the lead content, with [specific gravity](/source/specific_gravity) 5.2, which is more than [baryte](/source/baryte) but less than [cerussite](/source/cerussite). It dissolves in [hydrochloric acid](/source/hydrochloric_acid)<ref name=Dana/><ref name=AM57/> and it is not radioactive.<ref name=Webmin/>

== Occurrence and associations ==
Tsumcorite is a rare [secondary mineral](/source/Supergene_(geology)) in the [oxidized zone](/source/oxidized_zone) of some [arsenic](/source/arsenic)-bearing [hydrothermal](/source/hydrothermal) [lead](/source/lead)-[zinc](/source/zinc) deposits.<ref name=Dana/><ref name=HOM/><ref name=AM57/>

The [type locality](/source/Type_locality_(biology)) is the [Tsumeb](/source/Tsumeb) Mine, Tsumeb, Otjikoto Region, Namibia, where it is associated with [willemite](/source/willemite), [smithsonite](/source/smithsonite), [mimetite](/source/mimetite), [scorodite](/source/scorodite), [anglesite](/source/anglesite), [arseniosiderite](/source/arseniosiderite), [beaverite](/source/beaverite), [beudantite](/source/beudantite), [carminite](/source/carminite), [ludlockite](/source/ludlockite), [o'danielite](/source/o'danielite), [zincroselite](/source/zincroselite), [stranskiite](/source/stranskiite) and [leiteite](/source/leiteite).<ref name=HOM/>  At the [Puttapa Mine](/source/Beltana%2C_South_Australia) in Australia it occurs with [adamite](/source/adamite), [mimetite](/source/mimetite), [smithsonite](/source/smithsonite), [goethite](/source/goethite) and [quartz](/source/quartz).<ref name=HOM/> At the  [Kintore Open Cut](/source/Broken_Hill_Ore_Deposit), Broken Hill, Australia it occurs with [segnitite](/source/segnitite), [beudantite](/source/beudantite), [carminite](/source/carminite) and [mawbyite](/source/mawbyite).<ref name=AJM/>

== References ==
{{commons category| Tsumcorite}}
{{Reflist}}

Category:Arsenate minerals
Category:Lead minerals
Category:Zinc minerals
Category:Iron(II) minerals
Category:Monoclinic minerals
Category:Minerals in space group 12
Category:Minerals described in 1971

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