{{Short description|Rare zinc arsenate mineral}} {{Infobox mineral | name = Warikahnite | category = Arsenate minerals | boxwidth = | boxbgcolor = | image = Warikahnite-mf19c.jpg | imagesize = 260 | caption = Warikahnite, Tsumeb mine, Namibia, 0.6 × 0.4 × 0.1 cm | formula = Zn<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>·2H<sub>2</sub>O | IMAsymbol = War<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 = 510.04 g/mol | strunz = 8.CA.35 | system = Triclinic | class = Pinacoidal ({{overline|1}}) <br/><small>(same H-M symbol)</small> | symmetry = ''P''{{overline|1}} | unit cell = a = 6.71 Å, b = 8.98 Å <br/>c = 14.53 Å; α = 105.59° <br/>β = 93.44°, γ = 108.68°; Z = 4 | color = Pale yellow to colorless; honey-yellow; orange | habit = Acicular; radial | twinning = | cleavage = [001] perfect, [010] good, [100] good | fracture = Brittle | mohs = 2 | luster = Vitreous, waxy | refractive = n<sub>α</sub> = 1.747 n<sub>β</sub> = 1.753 n<sub>γ</sub> = 1.768 | opticalprop = Biaxial (+) | birefringence = δ = 0.021 | pleochroism = | 2V = 75° measured | streak = White | gravity = 4.28 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent | other = | references = <ref name=mineral_handbook>http://rruff.geo.arizona.edu/doclib/hom/warikahnite.pdf Mineral Handbook</ref><ref>http://webmineral.com/data/Warikahnite.shtml Webmineral</ref><ref>http://www.mindat.org/min-4244.html Mindat</ref><ref name= Fleischer>{{cite journal| last= Fleischer| first= Michael|author2=L. J. Cabri |author3=A. Pabst | year= 1980| title= New mineral names| journal= American Mineralogist| volume= 65| pages=406–408| url=http://www.minsocam.org/ammin/AM65/AM65_406.pdf| access-date= 2010-01-03}}</ref> }}
'''Warikahnite''' is a rare zinc arsenate mineral of the triclinic crystal system with Hermann-Mauguin notation {{overline|1}}, belonging to the space group P{{overline|1}}.<ref name=Pinch>{{cite journal| last= Pinch| first= William W.|date=July 2005| title= Warikahnite: some background on the cover specimen.| journal= The Mineralogical Record| publisher=The Mineralogical, Inc.| volume= 36| issue=4 | pages=315(1)}}</ref> It occurs in the Tsumeb mine in Namibia on corroded tennantite in the second oxidation zone under hydrothermal conditions in a dolomite-hosted polymetallic ore deposit.<ref name= Fleischer/><ref name=Anthony>Anthony, J. W., Bideaux, R. A., Bladh, K. W., and Nichols, M. C. (2000) Handbook of Mineralogy. Volume IV: Arsenates, Phosphates and Vanadates. Mineral Data Publishing Company, Tucson, Arizona, p. 644</ref> It is associated with adamite, stranskiite, koritnigite, claudetite, tsumcorite, and ludlockite. The origin of discovery was in a dolomite ore formation within an oxidized hydrothermal zone, in the E9 pillar, 31st level of the Tsumeb Mine in Namibia, Southwest Africa.<ref name=mineral_handbook/><ref name= Fleischer/> It has also been found at Lavrion, Greece and Plaka, Greece as microscopic white needles.<ref name=Pinch/>
==Discovery== [[Image:Warikahnite-177594.jpg|thumb|left|200px|Warikahnite, Tsumeb mine, Namibia, 0.9 × 0.4 × 0.1 cm]] Warikahnite was discovered by Clive Queit<ref name=Pinch/> at Tsumeb mine and was first described in 1979 by Keller, Hess, and Dunn.<ref name=mineral_handbook/><ref name= Fleischer/> The name "warikahnite" honors Walter Richard Kahn, who was born in 1911. He was from Bad Bayersoien, Germany, and he was a dealer and collector that specialized in Tsumeb minerals. He was honored due to his support of research into rare secondary minerals.<ref name=mineral_handbook/> The type material is located at the University of Stuttgart, the Smithsonian Institution, and Harvard University.<ref name= Fleischer/><ref name=Pinch/>
==Physical properties== Warikahnite has perfect cleavage on the c-axis {001}; and good cleavage on both the a- and b-axes ({100} and {010}).<ref name= Fleischer/> It has bladed subhedral crystals up to 3 × .5 × .5 mm, elongated on {100} and flattened on {010}, with a hardness of approximately 2 as presented in table two. Its specific gravity is 4.24 and it exhibits a colorless to pale yellow hue, along with a white streak and vitreous luster.<ref name=Pinch/> This triclinic {{overline|1}} specimen classified under the space group P{{overline|1}} features striated crystals up to two centimetres in radial to subparallel aggregates.<ref name=Anthony/> The Handbook of Mineralogy further states the cell dimensions of biaxial Warikahnite to be calculated as a = 6.710(1) Å, b = 8.989(2) Å, and c = 14.533(2) Å, with unit cell volume as 788.58 Å.<ref name=Pinch/>
==Crystal structure== thumb|left|Structure The crystal structure of Warikahnite, determined from diffractometer data, contained six various coordination polyhedra of zinc with components of As, O, and H<sub>2</sub>O; with the coordination numbers six, five, and four; and with five different combinations of ligand.<ref>Riffel, H., P. Keller, and H. Hess (1980) Die Kristallstruktur von Warikahnit, Zn<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>·2H<sub>2</sub>O Tschermaks Mineral. Petrog. Mitt., 27, 187–199 (in German with English abs)</ref> The "Die Kristallstruktur von Warikahnit" article also notes that the hydrogen bonds are discussed appertaining to both charge balance and infrared spectra. Recent data shows the Gladstone-Dale relation compatibility of warikahnite is ranked as superior (−0.010).<ref>{{Cite journal |author=Mandarino, Joseph A. |year=2006 |author-link=Joseph Anthony Mandarino |title=The Gladstone-Dale Compatibility of Arsenate Minerals |journal=Periodico di Mineralogia |volume=75 |issue=2–3 |pages=167–174}}</ref>
==Chemical composition== Warikahnite has the chemical formula Zn<sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>·2H<sub>2</sub>O. Along with arsenate ions (AsO<sub>4</sub>)<sup>3−</sup>, the infrared spectrum revealed H<sub>2</sub>O.<ref name=Fleischer/> These water molecules present in the warikahnite sample were determined by thermo gravimetric analysis, and lost at 365{{nbsp}}°C. Both H<sub>2</sub>O and (AsO<sub>4</sub>)<sup>3−</sup> readily dissolved when hot hydrochloric acid (HCL) or nitric acid (HNO<sub>3</sub>) were added to the specimen.<ref>Keller, P., Hess, H., and Dunn, P.J. (1979) Warikahnit, ein neues Mineral aus Tsumeb, Sudwestafrika. Neues Jahrbuch fur mineralogy, Monatshefte, 389–395. Abstracted in American Mineralogist, 65, 408</ref> After a microprobe analysis, the weight percent oxides were calculated as follows in the table directly below.<ref name=Fleischer/> {| class="wikitable" |- ! Chem For.|| Name || % |- | As<sub>2</sub>O<sub>5</sub> || (arsenic pentoxide) || 44.33% |- | ZnO || (zinc oxide) || 47.85% |- | MnO || (manganese oxide) || 0.40% |- | FeO || (iron oxide) || 0.19% |- | H<sub>2</sub>O || (water) || 6.32% |- | '''Total''' || || '''99.09%''' |}
==Geologic occurrence== Warikahnite's only known localities to date are the Tsumeb Mine in Namibia, South West Africa; and Plaka and Lavrion, Greece.<ref name=Pinch/> The first discovery of this type specimen in the mine was found with white koritnigite, blue stranskiite, pale to emerald-green cuprian adamite, crystals of helmutwinklerite, and white corroded crystals of claudetite, ludlockite, tsumcorite, and lavendulan; while the second acquisition was only linked to quartz.<ref name=Pinch/>
==See also== *List of minerals
==References== {{Reflist}} {{commons category| Warikahnite}}
==Literature== * Keller, P., H. Hess, and P.J. Dunn (1979) Warikahnit, Zn3[(H2O)2|(AsO4)2], ein neues Mineral aus Tsumeb, Südwestafrika. Neues Jahrb. Mineral., Monatsh., 389–395. * Riffel, H., P. Keller, and H. Hess (1980) Die Kristallstruktur von Warikahnit, Zn3[(H2O)2|(AsO4)2]. Tschermaks Mineral. Petrog. Mitt., 27, 187–199.
Category:Zinc minerals Category:Arsenate minerals Category:Triclinic minerals Category:Minerals in space group 2 Category:Minerals described in 1979