Some Observations on Assarsson's Z-phase and Its Structural Relations to Gyrolite, Truscottite, and Reyerite

J. A. Gard, T. Mitsuda1 and H. F. W. Taylor
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen, AB9 2UE, Scotland
1Permanent address: Materials Research Laboratory, Nagoya Institute of Technology, Gokisocho, Showa-ku, Nagoya, Japan

Summary: Z-phase was obtained hydrothermally at 120 °C by decomposition of Al-substituted tobermorite and by reaction of lime and colloidal silica. X-ray and electron diffraction show that the structural element is hexagonal, with a 9·65, c 15·3 Å, and good {0001} cleavage. Reversible water loss and lattice shrinkage occur on heating, the layer thickness (c) decreasing to 12.1 Å at 400 °C. For material in equilibrium with air of normal humidity, the composition is probably between CaO. 2SiO2. 1·7H2O and CaO. 2SiO2. 2H2O; Z = 8 for the structural element. New t.g. and infrared absorption data are presented; the infra-red spectrum closely resembles that of gyrolite, but OH ions attached only to Ca appear to be absent. Conditions of formation are discussed; if Z-phase has any stability field, it is below 120 °C. Crystal structures for Z-phase, gyrolite, and truscottite are suggested, based on the known structure of reyerite.

Mineralogical Magazine; December 1975 v. 40; no. 312; p. 325-333; DOI: 10.1180/minmag.1975.040.312.01
© 1975, The Mineralogical Society
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