# Arthurite

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{{Short description|Arsenate mineral}}
{{Infobox mineral
| name        = Arthurite
| category    = [Arsenate minerals](/source/Arsenate_minerals)
| image       = Arthurite on rock Hydrous basic copper iron arsenate Majuba Hill Pershing County Nevada 2231.jpg
| imagesize   = 
| caption     = 
| formula     = CuFe<sub>2</sub><sup>3+</sup>[(OH,O)(AsO<sub>4</sub>,PO<sub>4</sub>,SO<sub>4</sub>)]<sub>2</sub>·4H<sub>2</sub>O
|IMAsymbol=Atu<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.DC.15 
| system      = [Monoclinic](/source/Monoclinic)
| class       = Prismatic (2/m) <br/><small>(same [H-M symbol](/source/H-M_symbol))</small>
| symmetry    = ''P''2<sub>1</sub>/c
| unit cell   = a = 10.189(2), b = 9.649(2) <br/>c = 5.598(1)&nbsp;[Å] <br/>β = 92.16(2)°; Z&nbsp;=&nbsp;2
| color       = Apple-green to bluish-green
| habit       = Acicular, prismatic, spherical
| other =Opacity: transparent to translucent
| twinning    = 
| cleavage    = 
| fracture    = 
| tenacity    =
| mohs        = 3–4
| luster      = vitreous
| polish      = 
| refractive  = 
| opticalprop = Biaxial (+), may be biaxial (–)
| birefringence = 
| dispersion  = r > v
| pleochroism = X = colorless to pale green; Y = gray-green; Z = olive-green
| fluorescence= 
| absorption  = Z > Y > X. α = 1.736 β = 1.767 γ = 1.796
| 2V          = ~90°
| streak      = not reported
| gravity     = 
| density     = D(measured) = ~3.2<br>D(calculated) = 3.29
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| diaphaneity = 
| references  =
}}

'''Arthurite''' is a [mineral](/source/mineral) composed of [divalent](/source/divalent) [copper](/source/copper) and [iron](/source/iron) [ion](/source/ion)s in combination with trivalent [arsenate](/source/arsenate), [phosphate](/source/phosphate) and [sulfate](/source/sulfate) ions with hydrogen and oxygen.<ref name=Frost>Frost R. L., Duong L., Martens W. (2003) Molecular assembly in secondary minerals – [Raman spectroscopy](/source/Raman_spectroscopy) of the arthurite group species arthurite and whitmoreite. Neues Jahrbuch für Mineralogie, Monatshefte, 2003, 223–240.</ref> Initially discovered by Sir [Arthur Russell](/source/Sir_Arthur_Russell%2C_6th_Baronet) in 1954 at Hingston Down Consols mine in [Calstock](/source/Calstock), Cornwall, England,<ref name=Davis1964>Davis, R. J. & Hey, M. H. (1964) Arthurite, a new copper-iron arsenate from Cornwall. ''[Mineralogical Magazine](/source/Mineralogical_Magazine)'', 33, 937–941.</ref> arthurite is formed as a resultant mineral in the oxidation region of some copper deposits by the variation of [enargite](/source/enargite) or [arsenopyrite](/source/arsenopyrite).<ref name=Frost /> The chemical formula of Arthurite is [Cu](/source/copper)[Fe](/source/iron)<sub>2</sub><sup>3+</sup>([As](/source/arsenic)[O](/source/oxygen)<sub>4</sub>,[P](/source/phosphate)[O](/source/oxygen)<sub>4</sub>,[S](/source/sulfur)[O](/source/oxygen)<sub>4</sub>)<sub>2</sub>([O](/source/oxygen),[O](/source/oxygen)[H](/source/hydrogen))<sub>2</sub>·4[H](/source/hydrogen)<sub>2</sub>[O](/source/oxygen).<ref name=Palmer>Palmer, S.J., Frost R.L. (2011) The structure of the mineral arthurite CuFe23+(AsO4,PO4,SO4)2(O,OH)2·4H2O – A Raman spectroscopic study. Journal of Molecular Structure, 994, 283–288.</ref>

Arthurite is named after [Arthur W. G. Kingsbury](/source/Arthur_W._G._Kingsbury) (1906–1968), a British mineralogist, and Sir Arthur Russell (1878–1964), a collector of minerals.

==Introduction==
Arthurite was determined to be a uniquely new mineral by R.J. Davis and M.H. Hey in 1964 after its initial discovery.<ref name=Davis1964 /> A second specimen was confirmed by A.H Clark and R.H. Sillitoe (1969) from Potrerillos, Atacama Province, Chile in 1969.<ref name=Clark>Clark, A. H. & Sillitoe, R. H. (1969) Arthurite from Potrerillos, Atacama Province, Chile. Mineralogical Magazine, 37, 519–520.</ref> Subsequently, several other arthurite-like minerals have been discovered. There are variations in which the copper (Cu) ions are replaced with [cobalt](/source/cobalt) (Co), in the case of [cobaltarthurite](/source/cobaltarthurite), [manganese](/source/manganese) (Mn) replaces Cu in the case of [earlshannonite](/source/earlshannonite), iron (Fe) in the case of [bendadaite](/source/bendadaite) and [whitmoreite](/source/whitmoreite) and [zinc](/source/zinc) (Zn) in the case of [ojuelaite](/source/ojuelaite). Arthurite is the copper-dominant end-member of the arthurite group.

==Composition==
The theoretical chemical formula of Arthurite was originally determined to be Cu<sub>2</sub>Fe<sub>4</sub>(AsO<sub>4</sub>)<sub>3</sub>(O,OH)<sub>7</sub>•6H<sub>2</sub>O.<ref name=Davis1964 /> The breakdown of the composition of arthurite in weight percent oxides is given in Table 1.

Table 1. Chemical composition of Arthurite in weight percent oxides
{| class="wikitable"
|-
! Element !! Oxide !! Theoretical Percentage<ref name=Davis1964 /> !! Recalculated Percentage<ref name=Davis1969>Davis, R. J. & Hey, M. H. (1969) The cell-contents of arthurite redetermined. Mineralogical Magazine, 37, 520–521.</ref>
|-
| Copper || CuO|| 16.00|| 14.5
|-
| Iron || Fe<sub>2</sub>O<sub>3</sub>|| 32.12|| 30.1
|-
| Arsenic || As<sub>2</sub>O<sub>5</sub>|| 34.67|| 34.8
|-
| Hydrogen || H<sub>2</sub>O|| 17.21|| 20.6
|-
| Sum|| || 96.54|| 100
|-
|}

Arthurite crystallizes from an aqueous solution with whichever applicable anions are accessible in the solution.<ref name=Frost /> These available anions may be carbonate, arsenate, sulphate and phosphate.<ref name=Frost /> Some other minerals belonging to the arthurite group are cobaltarthurite, Co<sup>2+</sup>Fe<sup>3+</sup><sub>2</sub>(AsO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>•4H<sub>2</sub>O,<ref name=Jambor>Jambor, J.L., Viñals, Joan, Groat, Lee A., Raudsepp, Mati. (2002) Cobaltarthurite, Co2+Fe23+(AsO4,PO4,SO4)2(O,OH)2·4H2O, A New Member of the Arthurite Group. The Canadian Mineralogist, 40, 725–732.</ref> whitmoreite Fe<sup>2+</sup>Fe<sup>3+</sup><sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·4H<sub>2</sub>O, ojuelaite, ZnFe<sub>2</sub>(AsO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·4H<sub>2</sub>O, earlshannonite, (Mn,Fe)Fe<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·4H<sub>2</sub>O<ref name=Frost /> and bendadaite, Fe<sup>2+</sup>Fe<sup>3+</sup><sub>2</sub>(AsO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·4H<sub>2</sub>O.<ref name=Kolitsch>Kolitsch, U., Atencio, D., Chukanov, N.V., Zubkova, N.V., Menezes Filho, L.A.D., Coutinho, J.M.V., Birch, W.D., Schlüter, J., Pohl, D., Kampf, A.R., Steele, I.M., Favreau, G., Nasdala, L., Möckel, S., Giester, G., Pushcharovsky, D.Yu. (2010) Bendadaite, a new iron arsenate mineral of the arthurite group. Mineralogical Magazine, 74, 469–486.</ref> The optimal compositions of the members of the arthurite group can be represented by A<sup>2+</sup>Fe<sup>3+</sup><sub>2</sub>(XO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·4H<sub>2</sub>O<ref name=Raudsepp>Raudsepp, Mati & Pani, Elisabetta. (2002) The Crystal Structure of Cobaltarthurite, Co2+Fe23+(AsO4,PO4,SO4)2(O,OH)2·4H2O: A Rietveld Refinement. The Canadian Mineralogist, 40, 733–737.</ref> and are summarized in Table 2.

Table 2. Compositional breakdown of the arthurite group members
{| class="wikitable"
|-
! Mineral !! A-site !! X-site !! Reference
|-
| arthurite|| Cu<sup>2+</sup>|| As<sup>5+</sup>|| <ref name=Davis1964 />
|-
| [cobaltarthurite](/source/cobaltarthurite)|| Co<sup>2+</sup>|| As<sup>5+</sup>|| <ref name=Raudsepp />
|-
| [whitmoreite](/source/whitmoreite)|| Fe<sup>2+</sup>|| As<sup>5+</sup>|| <ref name=Frost />
|-
| [ojuelaite](/source/ojuelaite)|| Zn<sup>2+</sup>|| P<sup>5+</sup>|| <ref name=Frost />
|-
| [earlshannonite](/source/ojuelaite)|| Mn<sup>2+</sup>, Fe<sup>2+</sup>|| P<sup>5+</sup>|| <ref name=Frost />
|-
| [bendadaite](/source/bendadaite)|| Fe<sup>2+</sup>|| P<sup>5+</sup>|| <ref name=Kolitsch />
|}

==Structure==
Arthurite is of the [monoclinic](/source/monoclinic) space group: P2<sub>1/c</sub> with a = 10.189(2)Å, b = 9.649(2)Å, c = 5.598(1)Å and β = 92.16(2).<ref name=Frost /> The coordination polyhedron of the Cu<sup>2+</sup> ion is clearly tetragonally lengthened as compared to whitmoreite with the Phosphorus (P) and Arsenic (As).<ref name=Frost /> Figure 1 shows the crystal structure of arthurite.<ref name=Keller>Keller, P. & Hess, H. (1978) The crystal structure of arthurite, CuFe23+[(H2O)4|(OH)2|(AsO4)2]. Neues Jahrbuch für Mineralogie, Monatshefte und Abhandlungen, 133, 291–302.</ref>

==Physical properties==
Table 3. General and physical properties of arthurite

{| class="wikitable"
|-
! Attribute !! Data
|-
| Chemical formula|| CuFe<sub>2</sub><sup>3+</sup>(AsO<sub>4</sub>,PO<sub>4</sub>,SO<sub>4</sub>)<sub>2</sub>(O,OH)<sub>2</sub>•4H<sub>2</sub>O
|-
| Color|| apple-green to bluish green
|-
| Opacity|| transparent to translucent
|-
| Habit|| acicular, prismatic, spherical
|-
| Hardness|| 3–4 ([Mohs](/source/Mohs_scale_of_mineral_hardness) scale)
|-
| Luster|| Vitreous
|-
| Optical Class|| Biaxial (+), may be biaxial (–)
|-
| Pleochroism|| X = colorless to pale green; Y = gray-green; Z = olive-green
|-
| Orientation|| Y = b; Z ^ c = 10
|-
| Absorption|| Z > Y > X. α = 1.736 β = 1.767 γ = 1.796
|-
| Density|| D(meas.) = ~3.2 D(calc.) = 3.29
|-
| Space group|| P21/c. a = 10.189(2) b = 9.649(2) c = 5.598(1) β = 92.16(2)° Z = 2
|-
| 2V calculation|| ~90°
|}

==Geologic occurrence==
The first specimen on record was sent to the [British Museum of Natural History](/source/British_Museum_of_Natural_History), Department of Mineralogy by Sir Arthur Russell in 1954. The sample specimen was collected by Sir Russell from [Hingston Down](/source/Hingston_Down) Consols mine in [Calstock](/source/Calstock), [Cornwall](/source/Cornwall),
[England](/source/England).<ref name=Davis1964 /> A second sample was found in 1966 in the Potrerillos copper deposit, [Atacama Province](/source/Atacama_Province%2C_Chile), northern [Chile](/source/Chile).<ref name=Clark /> Each of these locations have [porphyritic](/source/porphyritic) copper deposits where circulating groundwater interacts with the cooling porphyritic intrusions and their fluids to form copper-bearing minerals and copper ore deposits. The copper ore found at the Chilean site was composed mainly of massive [djurleite](/source/djurleite) deposits that strongly oxidized to form [goethite](/source/goethite), minor [cuprite](/source/cuprite) and [malachite](/source/malachite).<ref name=Clark /> The arthurite formed as thin (0.1 – 0.5&nbsp;mm) and sparsely coated areas growing along the inner walls of minor fractures splitting through malachite-rich encased djurleite forms.<ref name=Clark />

==Biographic sketch==
Arthurite is named after two people, Arthur William Gerald Kingsbury and Sir Arthur Edward Ian Montagu Russell. Arthur Kingsbury was the son of a farmer in East Meon, Hampshire, England. He attended Bradfield College in Berkshire prior to an apprenticeship at a London law firm. He passed the bar exam in 1929 and became a solicitor at Sherborne and then later Crewkerne in the West of England. He began collecting minerals in 1927. After the war he accepted a position as a research assistant in the mineralogy department of the Oxford University Museum where he added 50 species to the list of minerals known to occur in Great Britain.<ref name=Embrey>Embrey, P.G. (1973) Memorial of Arthur William Gerald Kingsbury. American Mineralogist, 58, 3–4, 372–375.</ref> Sir Arthur Edward Ian Montagu Russell was born in 1878 and became the 6th Baronet of Swallowfield Park Reading when his older brother died in 1944. Sir Arthur attended the prestigious [Eton College](/source/Eton_College) and then studied chemistry at [King's College](/source/King's_College_London), London. During his life he amassed an amazing collection of minerals, many from the collections of others, but also from his own field work. When Sir Arthur died in 1964 his collection of 12,000 mineral specimens went to [The Natural History Museum](/source/British_Museum_of_Natural_History) in London with the stipulation that the collection not be dispersed, but remain as a British regional collection.<ref name=Hart>Hart, A.D. & Symes, R.F. (1991) Arthur Edward Ian Montagu Russell. Journal of the Russell Society, 4, 1.</ref>

==References==
{{reflist|30em}}
{{portalbar|Minerals|Cornwall}}
Category:Copper minerals
Category:Iron(III) minerals
Category:Arsenate minerals
Category:Phosphate minerals
Category:Sulfate minerals
Category:Tetrahydrate minerals
Category:Monoclinic minerals
Category:Minerals in space group 14

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