Simmonsite, Na2LiAlF6, a new mineral from the Zapot amazonite-topazzinnwaldite pegmatite, Hawthorne, Nevada, U.S.A
American Mineralogist
By: E.E. Foord, J. T. O’Connor, J.M. Hughes, S. J. Sutley, A.U. Falster, A.E. Soregaroli, F.E. Lichte, and D. E. Kile
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Abstract
Simmonsite, Na2LiAlF6, a new mineral of pegmatitic-hydrothermal origin, occurs in a late-stage breccia pipe structure that cuts the Zapot amazonite-topaz-zinnvvaldite pegmatite located in the Gillis Range, Mineral Co., Nevada, U.S.A. The mineral is intimately intergrown with cryolite, cryolithionite and trace elpasolite. A secondary assemblage of other alumino-fluoride minerals and a second generation of cryolithionite has formed from the primary assemblage. The mineral is monoclinic, P21 or P21/m, a = 7.5006(6) A??, b = 7.474(1) A??, c = 7.503(1) A??, ??= 90.847(9) ??, V=420.6(1) A??3, Z = 4. The four strongest diffraction maxima [d(A??), likl, I/I100] are (4.33, 111 and 111, 100); (1.877, 400 and 004, 90); (2.25, 13T, 113, 131 and 311, 70); and (2.65, 220, 202, 022, 60). Simmonsite is pale buff cream with white streak, somewhat greasy, translucent to transparent, Mohs hardness of 2.5-3, no distinct cleavage, subconchoidal fracture, no parting, not extremely brittle, Dm is 3.05(2) g/cm3, and Dc is 3.06(1) g/cm3. The mineral is biaxial, very nearly Isotropie, N is 1.359(1) for ?? = 589 nm, and birefringence is 0.0009. Electron microprobe analyses gave (wt%) Na = 23.4, Al = 13.9, F = 58.6, Li = 3.56 (calculated), with a total of 99.46. The empirical formula (based on 6 F atoms) is Na1.98Li1.00 ooAl|ooF6. The crystal structure was not solved, presumably because of unit-cell scale twinning, but similarities to the perovskite-type structure exist. The mineral is named for William B. Simmons, Professor of Mineralogy and Petrology, University of New Orleans, New Orleans.
Suggested Citation
Foord, E., O’Connor, J.T., Hughes, J., Sutley, S.J., Falster, A., Soregaroli, A., Lichte, F., Kile, D.E., 1999, Simmonsite, Na2LiAlF6, a new mineral from the Zapot amazonite-topazzinnwaldite pegmatite, Hawthorne, Nevada, U.S.A: American Mineralogist, v. 84, no. 5-6, p. 769-772.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Simmonsite, Na2LiAlF6, a new mineral from the Zapot amazonite-topazzinnwaldite pegmatite, Hawthorne, Nevada, U.S.A |
| Series title | American Mineralogist |
| Volume | 84 |
| Issue | 5-6 |
| Year Published | 1999 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | American Mineralogist |
| First page | 769 |
| Last page | 772 |