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The X-Ray Crystallography of Tavorite from the Tip Top Pegmatite, Custer, South Dakota

Published online by Cambridge University Press:  10 January 2013

Andrew C. Roberts
Affiliation:
Geological Survey of Canada, 601 Booth St., Ottawa, Ontario,Canada K1A 0E8
Pete J. Dunn
Affiliation:
Department of Mineral Sciences, Smithsonian Institution, Washington, D. C. 20560, U.S.A.
Joel D. Grice
Affiliation:
Mineral Sciences Division, National Museum of Natural Sciences, Ottawa, Ontario, Canada K1A 0M8
Dale E. Newbury
Affiliation:
Center for Analytical Chemistry, National Bureau of Standards, Gaithersburg, Maryland 20899, U.S.A.
Willard L. Roberts
Affiliation:
Museum of Geology, South Dakota School of Mines, Rapid City, South Dakota 57701, U.S.A.

Abstract

Bright apple green millimeter-sized crystals of tavorite from the Tip Top pegmatite, near Custer, South Dakota are triclinic, space group , with refined unit-cell parameters a = 5.340(2), b = 7.283(2), c = 5.110(2)Å, α = 109.29(2)°, β = 97.86(3)°, γ = 106.32(3)°, V = 174.1(3)Å3, a:b:c = 0.7332:1:0.7016, Z = 2, D(m) (suspension in methylene iodide) = 3.32(1) and D(x) = 3.33 g/cm3 (for the theoretical formula). A fully indexed X-ray powder pattern is presented. Semiquantitative electron microprobe and secondary ion mass spectroscopic analyses indicate a formula near end-member LiFe + 3(PO4)(OH). The Tip Top tavorite is biaxial positive, α = 1.795(5), β = 1.81(1), γ = 1.86(1), 2V(meas.) = 50(2)°, 2V(calc.) = 59°, XΛa ≃ 15°, YΛb ≃ 0°, and ZΛc ≃ 38°. There is no evidence for optical absorption, pleochroism or dispersion.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1988

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