Structure of the 30-sectored polygonal serpentine. A model based on TEM and SAED studies |
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Authors: | István Dódony |
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Institution: | Department of Mineralogy, E?tv?s Loránd University, Múzeum krt. 4/A, H-1088 Budapest, Hungary, HU
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Abstract: | Polygonal serpentine (PS) from selected serpentinite were studied using transmission electron microscopy. Fiber axis selected-area
electron diffraction (SAED) patterns and electron micrographs reveal orthogonal and monoclinic lizardite polytypes. The PS
models by Chisholm (1992) and Baronnet et al. (1994) do not fit SAED measurements. Experimental results are matched with calculated
diffraction geometry and intensities, as well as with simulated images, indicating inversion of the tetrahedral layer at sector
boundaries. The structural relationships between chrysotile and PS are discussed.
Two types of 30-sectored PS are distinguished. In “regular PS” the fiber axis is 100], in “helical PS” the fiber axis points
into a uν0] direction with large u value (u≫ν). Helical PS can be regarded as a lizardite analogue of helical chrysotile.
Received December 6, 1995/Revised, accepted May 8, 1996 |
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