gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1976.040.313.08 Effect of Pressure on Reversible Solid-Solid Transitions in Nepheline and Carnegieite Cohen Lewis H. 1 Klement William Jr. 2 Department of Earth Sciences, University of California, Riverside 92502 School of Engineering and Applied Science, University of California, Los Angeles 90024. Now on leave at National Physical Research Laboratory, Pretoria, Republic of South Africa 3 1976 40 313 487 492 3 2 1975 21 4 1975 Copyright © 1976, The Mineralogical Society 1976 Summary

Differential thermal analysis of a rapidly reversible transition in carnegieite to 7 kbar shows the transition temperature increases from < ˜ 707 °C (on heating) at 1 bar with initial slope ≈ 8·0 deg kbar−1 and anomalous curvature (d2T/dp2 > 0), with hysteresis between heating and cooling signals that decreases with pressure. DTA of rapidly reversible transitions in nepheline shows the very subtle transition near 185 °C (on heating) at 1 bar decreases with pressure to ≈ 170 °C near 2–3 kbar and hardly varies in temperature up to 6 kbar; and the higher temperature transition increases from ≈ 872 °C (on heating) at 1 bar with slope ≈ 25 deg kbar−1, to 5 kbar, with the hysteretic interval remaining essentially unchanged in the investigated range.