Effect of Pressure on Reversible Solid-Solid Transitions in Nepheline and Carnegieite

Lewis H. Cohen1 and William Klement Jr.2
1 Department of Earth Sciences, University of California, Riverside 92502
2 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

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.

Mineralogical Magazine; March 1976 v. 40; no. 313; p. 487-492; DOI: 10.1180/minmag.1976.040.313.08
© 1976, The Mineralogical Society
Mineralogical Society (www.minersoc.org)