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Twinning in hydrothermally grown synthetic quartz as revealed by etch structures
Author(s) -
Kotru P. N.,
Kachroo S. K.,
Raina K. K.
Publication year - 1985
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.2170200108
Subject(s) - crystal twinning , crystallography , quartz , crystallization , materials science , lattice (music) , crystal (programming language) , parallelogram , crystal structure , mineralogy , geology , chemistry , composite material , microstructure , physics , hinge , organic chemistry , classical mechanics , computer science , acoustics , programming language
Etch structures obtained by HF etching on habit and cleaved rhombohedral surfaces of synthetic quartz grown by hydrothermal crystallization technique, indicative of twinning in them are described, illustrated and discussed. The twin traces appear in the form of lines of dis‐continuity in [1121] and [1211] directions. Etch pits within the parallelogram‐shaped bound areas are oppositely oriented with respect to those on the rhombohedral surface of the main crystal. The form of twinning observed is found to be of parallel lattice type and the surface within and outside the bound areas are coplanar in most of the cases. The rhombohedral faces of the twinned crystals are found to be geometrically related to each other as if one part is derived from the other by a rotation of 180° about [1210] direction. Discontinuation in the crystal lattice along the twin trace is evidenced by obstructions in the normal development of an etch pit. Deep penetration of twin traces and parallelogram‐shaped regions, enclosing etch pits of opposite orientation (twinned areas), well within the crystal structure is demonstrated by comparison of etch patterns on matched rhombohedral cleavages and the results on their successive etching. The type of twinning displayed by the crystals is discussed in the light of models suggested. Causes for the generation of twinning in synthetic quartz are explained to lie in the availability of twinned nuclei in the seed plates used for hydrothermal crystallization of quartz.