Phase de Laves dans la première opale CT bidisperse |
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| Authors: | Jean-Pierre Gauthier Emmanuel Fritsch Bertha Aguilar-Reyes Alain Barreau Bernard Lasnier |
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| Affiliation: | 1. Laboratoire de dynamique de la lithosphère, université Claude-Bernard, Lyon-1, 43, bd du 11-Novembre-1918, 69622 Villeurbanne cedex, France;2. Laboratoire de physique cristalline et Centre de microcaractérisation, institut des matériaux Jean-Rouxel (IMN), université de Nantes, 2, rue de la Houssinière, BP 32229, 44322 Nantes cedex 3, France;3. Laboratoire de planétologie et géodynamique & laboratoire de gemmologie, université de Nantes, 2, rue de la Houssinière, BP 92208, 44322 Nantes cedex 3, France |
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| Abstract: | A Mexican opal from the state of Jalisco has a bidisperse, perfectly ordered structure with framboid silica lepispheres of two different diameters. Its structure has been determined by the observation of a vicinal section, close to a dense plane. Fresh breaks along a vicinal plane emphasized regular steps, which were studied by means of SEM. We have been able to propose unit cell models, theoretical positions of the two sets of spheres, and probable space group, P63/mmc. This structure arranges similarly to that of a diatomic compound having an AB2 stoichiometry and corresponds to a cubic (MgCu2-type) or hexagonal (MgZn2-type) Laves phase. This last variety seems to be the most probable structure. To cite this article: J.-P. Gauthier et al., C. R. Geoscience 336 (2004). |
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| Keywords: | opale noble CT silice structure bidisperse phases de Laves precious opal CT silica bidisperse structure Laves phases |
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