Jadeite, analcite, nepheline, and albite at high temperatures and pressures

The equilibrium P-T curves for the following have been determined: albite = jadeite + quartz; albite + nepheline = 2 jadeite; analcite = jadeite + water. The curves for albite = jadeite + quartz is P(bars) = 6800 + 18.6 T degrees C. The reaction albite + nepheline = 2 jadeite is shown by P(bars) = -4000 + 25 T degrees C, and the curve for the reaction analcite = jadeite + H ~2~ O has been reversibly located at temperatures of both 500 degrees and 600 degrees . The slope of the reaction is P(bars) = 9.5 T degrees C + 6000 and is consistent with theoretical considerations; the other curves agree with previously-determined curves. The curve for the reaction analcite = albite + nepheline + water has been located to within + or -3 kilobars at 600 degrees C.