Pressure effect on water content of amphiboles

Abstract
The water content of synthetic amphibole (richterite50 + tremolite50 solid solution) markedly increases with increase in the vapor pressure in the range from 5 to 20 kb at fixed temperatures. Temperature change from 750°C to 900°C at fixed pressures does not affect the water content of synthetic amphiboles. The water content of common hornblende from ultramafic‐mafic rocks is found to be always higher than that from granitic rocks. This difference indicates a difference in the confining pressure of formation of two rock types.