Skip to content
Licensed Unlicensed Requires Authentication Published by De Gruyter February 9, 2017

Kegginite, Pb3Ca3[AsV12O40(VO)]·20H2O, a new mineral with a novel ε-isomer of the Keggin anion

Anthony R. Kampf, John M. Hughes, Barbara P. Nash and Joe Marty
From the journal American Mineralogist


Kegginite, Pb3Ca3[AsV12O40(VO)]·20H2O, is a new mineral species from the Packrat mine, near Gateway, Mesa County, Colorado, U.S.A. It is a secondary mineral found on asphaltum in a montroseite- and corvusite-bearing sandstone. Other secondary minerals found in close association with kegginite are ansermetite, gypsum, mesaite, and sherwoodite. Crystals of kegginite are orange-red simple hexagonal tablets. The streak is pinkish-orange, the luster is vitreous, the Mohs hardness is about 2, the tenacity is brittle, fracture is irregular, cleavage is good on {001}, and the calculated density is 2.69 g/cm3. Kegginite is optically uniaxial (–) with pleochroism: O orange-red and E red-orange; E < O. Electron microprobe analyses yielded the empirical formula Pb2.98Ca2.39Mg0.56V13.05As0.95O61H40.15. Kegginite is trigonal, P3¯, with a = 14.936(5), c = 15.846(5) Å, V = 3061(2) Å3, and Z = 2. The crystal structure of kegginite (R1 = 0.064 for 1356 Fo > 4σF reflections) contains a [As5+V125+O40(VO)]12 polyoxometalate cluster, which is a mono-capped Keggin ε-isomer.


Reviewers Michael Schindler and Henrik Friis are thanked for constructive comments, which improved the manuscript. Editorial handling by Fernando Colombo is greatly appreciated. This study was funded, in part, by the John Jago Trelawney Endowment to the Mineral Sciences Department of the Natural History Museum of Los Angeles County and by grant NSF-MRI 1039436 from the National Science Foundation to J.M.H. Jim Fisher, General Mine Superintendent, Denison Mines, allowed us to obtain specimens for study.

References cited

Bakri, R., Booth, A., Harle, G., Middleton, P.S., Wills, C., Clegg, W., Harrington, R.W., and Errington, R.J. (2012) Rational addition of capping groups to the phosphomolybdate Keggin anion [PMo12O40]3− by mild, non-aqueous reductive aggregation. Chemical Communications, 48, 2779–2781.10.1039/c2cc17670jSearch in Google Scholar PubMed

Brese, N.E., and O’Keeffe, M. (1991) Bond-valence parameters for solids. Acta Crystallographica, B47, 192–197.10.1107/S0108768190011041Search in Google Scholar

Burla, M.C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G.L., Giacovazzo, C., Mallamo, M., Mazzone, A., Polidori, G., and Spagna, R. (2012) SIR2011: a new package for crystal structure determination and refinement. Journal of Applied Crystallography, 45, 357–361.10.1107/S0021889812001124Search in Google Scholar

Carter, W.D., and Gualtieri, J.L. (1965) Geology and uranium–vanadium deposits of the La Sal quadrangle, San Juan County, Utah, and Montrose County, Colorado. U.S. Geological Survey Professional Paper, 508.10.3133/pp508Search in Google Scholar

Cronin, L., and Müller, A. (2012) From serendipity to design of polyoxometalates at the nanoscale, aesthetic beauty and applications. Chemical Society Reviews, 41, 7333–7334.10.1039/c2cs90087dSearch in Google Scholar PubMed

Ercit, T.S., and Hawthorne, F.C. (1995) Murataite, a UB12 derivative structure with condensed Keggin molecules. Canadian Mineralogist, 33, 1223–1229. Evans, H.T. Jr., and Garrels, R.M. (1958) Thermodynamic equilibria of vanadium in aqueous solution as applied to the interpretation of the Colorado Plateau ore deposits. Geochimica et Cosmochimica Acta, 15, 131–149.Search in Google Scholar

Kampf, A.R., Hughes, J.M., Nash, B.P., Wright, S.E., Rossman, G.R., and Marty, J. (2014) Ophirite, Ca2Mg4[Zn2Mn23+(H2O)2(Fe3+W9O34)2]46H2O, a new mineral with a heteropolytungstate tri-lacunary Keggin anion. American Mineralogist, 98, 1045–1051.10.2138/am.2014.4699Search in Google Scholar

Kampf, A.R., Hughes, J.M., Nash, B.P., and Marty, J. (2016a) Vanarsite, packratite, morrisonite, and gatewayite: four new minerals containing the [[As3+V124+,5+As65++O51] heteropolyanion, a novel polyoxometalate cluster. Canadian Mineralogist, 54, 145–162.10.3749/canmin.1500062Search in Google Scholar

Kampf, A.R., Hughes, J.M., Nash, B.P., and Marty, J. (2016b) Mesaite, CaMn52+(V2O7)312H2O, (V2O7)312H2O, a new vanadate mineral from the Packrat mine, near Gateway, Mesa County, Colorado, USA. Mineralogical Magazine, 80, 10.1180/minmag.2016.080.095.Search in Google Scholar

Keggin, J.F. (1934) The structure and formula of 12-phosphotungstic acid. Proceedings of the Royal Society A, 144, 75–100.Search in Google Scholar

Pouchou, J.-L., and Pichoir, F. (1991) Quantitative analysis of homogeneous or stratified microvolumes applying the model “PAP.” In K.F.J. Heinrich and D.E. Newbury, Eds., Electron Probe Quantitation, pp. 3l–75. Plenum Press, New York.10.1007/978-1-4899-2617-3_4Search in Google Scholar

Schindler, M., and Hawthorne, F.C. (2001) A bond-valence approach to the structure, chemistry, and paragenesis of hydroxyl-hydrated oxysalt minerals. I. Theory. Canadian Mineralogist, 39, 1225–1242.10.2113/gscanmin.39.5.1225Search in Google Scholar

Schindler, M., Hawthorne, F.C., and Baur, W.H. (2000) Crystal chemical aspects of vanadium: Polyhedral geometries, characteristic bond valences, and polymerization of (VOn) polyhedral. Chemistry of Materials, 12, 1248–1259.10.1021/cm990490ySearch in Google Scholar

Shawe, D.R. (2011) Uranium-vanadium deposits of the Slick Rock district, Colorado. U.S. Geological Survey Professional Paper, 576-F.10.3133/pp576FSearch in Google Scholar

Sheldrick, G.M. (2008) A short history of SHELX. Acta Crystallographica, A64, 112–122.10.1107/S0108767307043930Search in Google Scholar PubMed

Song, Y.-F., and Tsunashima, R. (2012) Recent advances on polyoxometalate-based molecular and composite materials. Chemical Society Reviews, 41, 7384–7402.10.1039/c2cs35143aSearch in Google Scholar PubMed

Received: 2016-4-28
Accepted: 2016-8-24
Published Online: 2017-2-9
Published in Print: 2017-2-1

© 2017 by Walter de Gruyter Berlin/Boston