Curvature of Gypsum Crystals Induced by Growth in the Presence of Impurities

Caterina Rinaudo, Marinella Franchini-Angela and Roland Boistelle
Dipartimento di Scienze della Terra, Via S. Massimo 24, 10123 Torino, Italy
Centre de Recherche sur les Mécanismes de la Croissance Cristalline, Campus Luminy, Case 913, 13288 Marseilte Cedex 9, France

Abstract: Gypsum crystals were grown at 25, 35, and 45 °C from solutions containing different ionic impurities (Mg2+, Na+, Cd2+). Curved gypsum crystals formed from the solutions enriched in magnesium or cadmium, whereas, in the presence of sodium, gypsum always grew undeformed. The mechanism of the curvature is described and an interpretation based on crystallographic considerations is given. Curvature is the result of impurity incorporation followed by crack formation and mechanical twinning which releases the internal stresses.

Keywords: gypsum • curved crystals • mechanical twins • impurity absorption

Mineralogical Magazine; September 1989 v. 53; no. 372; p. 479-482; DOI: 10.1180/minmag.1989.053.372.08
© 1987, The Mineralogical Society
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