| 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. |
| Genre: | Article |
| ProdID: | 70021014 |
| Citation Author: | Foord, E. E.; O'Connor, J. T.; Hughes, J. M.; Sutley, S. J.; Falster, A. U.; Soregaroli, A. E.; Lichte, F. E.; Kile, D. E. |
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| Citation End Page: | 772 |
| Citation Issue: | 5-6 |
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| Citation Language: | English |
| Citation Larger Work Title: | American Mineralogist |
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| Citation Number Of Pages: | 4 |
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| Citation Search Results Text: | Simmonsite, Na2LiAlF6, a new mineral from the Zapot amazonite-topazzinnwaldite pegmatite, Hawthorne, Nevada, U.S.A; 1999; Article; Journal; American Mineralogist; Foord, E. E.; O‘Connor, J. T.; Hughes, J. M.; Sutley, S. J.; Falster, A. U.; Soregaroli, A. E.; Lichte, F. E.; Kile, D. E. |
| Citation Start Page: | 769 |
| Citation Volume: | 84 |
| Citation Year: | 1999 |
| Type: | citation/reference |
| Text: | Simmonsite, Na2LiAlF6, a new mineral from the Zapot amazonite-topazzinnwaldite pegmatite, Hawthorne, Nevada, U.S.A; 1999; Article; Journal; American Mineralogist; Foord, E. E.; O‘Connor, J. T.; Hughes, J. M.; Sutley, S. J.; Falster, A. U.; Soregaroli, A. E.; Lichte, F. E.; Kile, D. E. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Fri, 1 Jan 1999 00:00 -0600 |
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