| Abstract: | Esperanzaite, ideally NaCa2Al2(As5+O4)2F4(OH)??2H2O, Z = 2, is a new mineral species from the La Esperanza mine, Durango State, Mexico. The mineral occurs as blue-green botryoidal crystalline masses on rhyolite, with separate spheres up to 1.5 mm in diameter. The Mohs hardness is 4 1/2 , and the specific gravity, 3.24 (obs.) and 3.36(3) (calc.). Optical properties were measured in 589 nm light. Esperanzaite is biaxial (-), X = Y = Z = colorless, ?? 1.580(1), ?? 1.588(1), and ?? 1.593(1); 2V(obs) is 74(1)??and 2V(calc) is 76.3??. The dispersion is medium, r < v, and the optic axes are oriented according to a ?? Z = +50.5??, b = Y, c ?? X = +35??. The strongest five X-ray-diffraction maxima in the powder pattern [d in A??(I)(hkl)] are: 2.966(100)(131, 311, 031), 3.527(90)(220), 2.700(90)(221,002,040), 5.364(80)(001,020) and 4.796(80)(011). Esperanzaite is monoclinic, a 9.687(5), b 10.7379(6), c 5.5523(7) A??, ?? 105.32(1)??, space group P21/m. The atomic arrangement of esperanzaite was solved by direct methods and Fourier analysis (R = 0.032). The Fundamental Building Block (FBB) is formed of [001] stacks of heteropolyhedral tetramers; the tetramers are formed of two arsenate tetrahedra and two Al octahedra, corner-linked in four-member rings. The FBBs are linked by irregular Na??5 and Ca??8 polyhedra. |
| Genre: | Article |
| ProdID: | 70021871 |
| Citation Author: | Foord, E. E.; Hughes, J. M.; Cureton, F.; Maxwell, C. H.; Falster, A. U.; Sommer, A. J.; Hlava, P. F. |
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| Citation End Page: | 72 |
| Citation Issue: | 1 |
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| Citation Language: | English |
| Citation Larger Work Title: | Canadian Mineralogist |
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| Citation Number Of Pages: | 6 |
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| Citation Search Results Text: | Esperanzaite, NaCa2Al2(As5+O4)2F4(OH)??2H2O, a new mineral species from the La Esperanza mine, Mexico: Descriptive mineralogy and atomic arrangement; 1999; Article; Journal; Canadian Mineralogist; Foord, E. E.; Hughes, J. M.; Cureton, F.; Maxwell, C. H.; Falster, A. U.; Sommer, A. J.; Hlava, P. F. |
| Citation Start Page: | 67 |
| Citation Volume: | 37 |
| Citation Year: | 1999 |
| Type: | citation/reference |
| Text: | Esperanzaite, NaCa2Al2(As5+O4)2F4(OH)??2H2O, a new mineral species from the La Esperanza mine, Mexico: Descriptive mineralogy and atomic arrangement; 1999; Article; Journal; Canadian Mineralogist; Foord, E. E.; Hughes, J. M.; Cureton, F.; Maxwell, C. H.; Falster, A. U.; Sommer, A. J.; Hlava, P. F. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Fri, 1 Jan 1999 00:00 -0600 |
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