Compression of pyrope

Abstract

Unit-cell parameters have been determined on a single crystal of pyrope mounted in a diamond-anvil cell at pressures from one atm to 50 kbar. From a least-squares fit ofthese data to a third-order Birch-Murnaghan equation of state, a value for the bulk modulus of pyrope (Kr: 1.75 Mbar) and its pressure derivative (K'r:4.5) were calculated. The bulk modulus is in good agreement with two other determinations using cubic-anvil and acoustic techniques but does not agree with another determination using single-crystal diamond-anvil techniques. It appears possible to obtain reasonable values and errors for K'r wrth diamond-anvil techniques at low pressures (<50 kbar), even for minerals with large values of K., when complementary acoustic data are available.