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Sewardite

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Terry M. Seward
Formula:
CaFe23+(AsO4)2(OH)2
System:
Orthorhombic
Colour:
Dark red to light orange
Lustre:
Vitreous
Member of:
Name:
Named in honour of Terry Maxwell Seward (b. 1940), Canadian geochemist, Professor of Geochemistry, Institut für Mineralogie und Petrographie, ETH (Swiss Federal Institute of Technology), Zürich, Switzerland. Seward’s research focuses on the chemistry of fluids on and in the earth’s crust, including low temperature aqueous systems, metal speciation, dispersion of heavy metals connected with toxic waste disposal and sea-floor hydrothermal systems.
The calcium analogue of Carminite.

Classification of Sewardite

Approved
8.BH.30

8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
H : With medium-sized and large cations, (OH,etc.):RO4 = 1:1
mindat.org URL:
http://www.mindat.org/min-11128.html
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Type Occurrence of Sewardite

Physical Properties of Sewardite

Vitreous
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
Dark red to light orange
Streak:
Reddish-brown

Crystallography of Sewardite

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Cccm
Cell Parameters:
a = 16.461Å, b = 7.434Å, c = 12.131Å
Ratio:
a:b:c = 2.214 : 1 : 1.632
Unit Cell Volume:
V 1,484.48 ų (Calculated from Unit Cell)

Chemical Properties of Sewardite

Formula:
CaFe23+(AsO4)2(OH)2
Essential elements:
All elements listed in formula:

Relationship of Sewardite to other Species

Member of:
Other Members of Group:
CarminitePbFe23+(AsO4)2(OH)2
CrimsonitePbFe23+(PO4)2(OH)2
8.BH.05ThadeuiteCa(Mg,Fe2+)3(PO4)2(OH,F)2
8.BH.10DurangiteNaAl(AsO4)F
8.BH.10IsokiteCaMg(PO4)F
8.BH.10LacroixiteNaAl(PO4)F
8.BH.10MaxwelliteNaFe3+(AsO4)F
8.BH.10PanasqueiraiteCaMg(PO4)(OH,F)
8.BH.10TilasiteCaMg(AsO4)F
8.BH.15DrugmanitePb(Fe3+,Al)2(PO4)2(OH)2
8.BH.20Bjarebyite(Ba,Sr)(Mn2+,Fe2+,Mg)2Al2(PO4)3(OH)3
8.BH.20CirroliteCa3Al2(PO4)3(OH)3 (?)
8.BH.20KulaniteBa(Fe2+,Mn2+,Mg)2(Al,Fe3+)2(PO4)3(OH)3
8.BH.20PenikisiteBa(Mg,Fe2+,Ca)2Al2(PO4)3(OH)3
8.BH.20PerloffiteBa(Mn2+,Fe2+)2Fe23+(PO4)3(OH)3
8.BH.20JohntomaiteBaFe22+Fe23+(PO4)3(OH)3
8.BH.25Bertossaite(Li,Na)2(Ca,Fe2+,Mn2+)Al4(PO4)4(OH,F)4
8.BH.25Palermoite(Li,Na)2(Sr,Ca)Al4(PO4)4(OH)4
8.BH.30CarminitePbFe23+(AsO4)2(OH)2
8.BH.35AdeliteCaMg(AsO4)(OH)
8.BH.35ArsendescloizitePbZn(AsO4)(OH)
8.BH.35AustiniteCaZn(AsO4)(OH)
8.BH.35CobaltaustiniteCaCo(AsO4)(OH)
8.BH.35ConichalciteCaCu(AsO4)(OH)
8.BH.35DuftitePbCu(AsO4)(OH)
8.BH.35GabrielsonitePbFe(AsO4)(OH)
8.BH.35NickelaustiniteCa(Ni,Zn)(AsO4)(OH)
8.BH.35TangeiteCaCu(VO4)(OH)
8.BH.35GottlobiteCaMg(VO4,AsO4)(OH)
8.BH.35HermannroseiteCaCu(PO4)(OH)
8.BH.40ČechitePb(Fe2+,Mn2+)(VO4)(OH)
8.BH.40DescloizitePb(Zn,Cu)(VO4)(OH)
8.BH.40MottramitePbCu(VO4)(OH)
8.BH.40PyrobelonitePbMn2+(VO4)(OH)
8.BH.45BayldonitePbCu3(AsO4)2(OH)2
8.BH.45VésigniéiteBaCu3(VO4)2(OH)2
8.BH.50PaganoiteNiBi(AsO4)O
8.BH.55JagoweriteBaAl2(PO4)2(OH)2
8.BH.60Attakolite(Ca,Sr)Mn(Al,Fe)4(HPO4,PO4)3(SiO4,PO4)(OH)4
8.BH.65LeningraditePbCu3(VO4)2Cl

Other Names for Sewardite

Name in Other Languages:
German:Sewardit
Simplified Chinese:砷钙铁矿
Spanish:Sewardita
Traditional Chinese:砷鈣鐵礦

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Sewardite

Reference List:
Roberts, A.C., Cooper, M.A., Hawthorne, F.C., Criddle, A.J., Stirling, J.A.R. (2002) Sewardite, CaFe3+2(AsO4)2(OH)2, the Ca-analogue of carminite, from Tsumeb, Namibia: description and crystal structure. Canadian Mineralogist: 40: 1191-1198.

Kolitsch, U. (2002) Sewardite from the Mina Ojuela, Mexico: a second occurrence. Lapis 27(12), 43 (in German).

Internet Links for Sewardite

Localities for Sewardite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
France
 
  • Limousin
    • Haute-Vienne
      • Nantiat
        • Vaulry
          • Vaulry Mines
Patrice Queneau Collection
Mexico
 
  • Durango
    • Mun. de Mapimí
      • Mapimí
Kolitsch, U. (2002): Sewardite from the Mina Ojuela, Mexico: a second occurrence. Lapis 27 (12), 43. (in German). Mineralogical Record (2003) 34:5 The Ojuela Mine
  • Sonora
    • Mun. de Benjamin Hill
Mikhail Murashko data
    • Mun. de Trincheras
      • La Mur
www.mindat.org/mesg-7-59761.html
Namibia (TL)
 
  • Otjikoto Region (Oshikoto)
    • Tsumeb
Can Min 40 (2002), 1191
Mineral and/or Locality  
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