Synthesis of K2SiSi3O9 with Silicon in 4- and 6-Coordination

N. Kinomura, S. Kume and M. Koizumi
College of General Education and Institute of Scientific and Industrial Research, Osaka University, Toyonaka, 560, Japan

Summary: Two kinds of vitreous material with composition K2GeSi3O9 and K2Si4O9 were treated under conditions of high temperature and pressure. The X-ray diffraction patterns of the products were similar to that of K2TiSi3O9, which has the wadeite, K2ZrSi3O9, structure.

A natural crystal of K-feldspar was also treated under the same conditions. The product was found to consist of three phases, coesite, kyanite, and the above-mentioned K2Si4O9. Since Zr ions in wadeite are in a 6-coordinated site, one-quarter of Si ions in K2Si4O9 are considered to be in 6-coordination. This is the first silicate in which Si ions occupy sites of 4- and 6-coordinations in one crystal at the same time.

Mineralogical Magazine; December 1975 v. 40; no. 312; p. 401-404; DOI: 10.1180/minmag.1975.040.312.09
© 1975, The Mineralogical Society
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