Synthesis of K2SiSi3O9 with silicon in 4- and 6-coordination

SummaryTwo 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.

Architecture of the Earth

Daly’s earth model has a solid crystalline crust varying in thickness but not exceeding fifty miles. This crust encloses a continuous layer of vitreous rock, relatively thin, which rests on a denser vitreous material. The heavier substratum surrounds a so‐called “iron core” possibly crystallized by high pressures of the interior. This vitreous subcrust has some properties of a solid; hence, it behaves more or less like a rigid mass.