Journal of Applied Crystallography

Volume 35, Part 4 (August 2002)

research papers

 

Triangular dendrites of LiAlSiO₄-SiO₂: evolution between threefold- and sixfold-symmetric morphologies

S. R. Zhao, J. Tan, J. Y. Wang, X. B. Hu and H. Liu

Abstract: A special kind of triangular dendrite of LiAlSiO₄-SiO₂ (or Li_1-xAl_1-xSi_1+xO₄, 0 x 1) in matt glaze has been observed by DIC (differential interference contrast) microscopy. This triangular dendrite is -quartz with a sixfold-symmetric structure. For polyhedral crystals, a crystal with threefold-symmetric structure prefers to develop a hexagonal prismatic habit rather than a trigonal prismatic habit, because a trigonal prism has a higher surface energy than a hexagonal prism. However, for dendritic crystals, a special kind of triangular dendrite, with a pattern formed by the aggregation of many small triangles, can develop. As supercooling decreases, -quartz can develop a series of morphologies with different surface energies, from snowflake-shaped dendrite to triangular dendrite, and finally to a polyhedral crystal in the form of a hexagonal prism. This series of crystal morphologies shows a morphological evolution from dendrite to polyhedral crystal, and also shows a morphological evolution between sixfold and threefold symmetries.

Keywords: minerals; crystal morphology; crystal habit; -quartz; dendrite; differential interference contrast.

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