Vochtenite, (Fe2+,Mg)Fe3+[UO2/PO4]4(OH). 12–13 H2O, a New Uranyl Phosphate Mineral from Wheal Basset, Redruth, Cornwall, England

P. C. Zwaan, C. E. S. Arps and E. de Grave
Rijksmuseum van Geologie en Mineralogie, Hooglandse Kerkgracht 17, 2312 HS Leiden, The Netherlands
Laboratorium voor Magnetisme, Rijksuniversiteit Gent, Proeftuinstraat 42, 9000 Gent, Belgium

Abstract: Vochtenite, a new mineral from the Basset Mine, southeast of Camborne in Cornwall, England, is a ferrous-ferric magnesium-bearing hydroxy uranyl phosphate mineral. It is monoclinic with a = 12.606, b = 19.990, c = 9.990 Å, β = 102.31° Z = 3; the ideal formula is: (Fe2+,Mg)Fe3+[UO2/PO4]4(OH)·12–13 H2O. The strongest lines in the X-ray powder diffraction pattern are: 9.998(100)(020), 4.999(30)(040), 4.892(45)(002), 3.475(70)(311), 3.333(50)(060), 3.087(40)(232), 2.205(40)(244¯) and 2.111(45)(344¯, 471¯). Vochtenite is brown in colour with a bronzy lustre and is non-fluorescent. Mohs hardness is 2.5 and the density (calc.) = 3.663 g/cm3. There is a prominent (010) cleavage. Vochtenite is optical biaxial negative, 2V (calc.) = 89(3)° its dispersion is indiscernible. Refractive indices are α = 1.575(2), β = 1.589(2), γ = 1.603(2), and the pleochroism is very weak. Orientation X(α)∥b is perpendicular to (010) and Z(γ)∧c is small. The mineral occurs as subparallel (0.5–1.0 mm) crystal aggregates with a pseudo-quadratic outline. The mineral is named vochtenite after Prof. Dr. Ing. R. F. C. Vochten of the State University of Antwerpen, Belgium.

Keywords: vochtenite • new mineral • uranyl phosphate group • Wheal Basset • Cornwall • England

Mineralogical Magazine; September 1989 v. 53; no. 372; p. 473-478; DOI: 10.1180/minmag.1989.053.372.07
© 1987, The Mineralogical Society
Mineralogical Society (www.minersoc.org)