views updated

cristobalite A high temperature form of quartz SiO2 which has a stability field at atmospheric pressure above 1470°C and below 1713°C, at which latter temperature cristobalite melts and the quartz liquidus is reached; sp. gr. 2.32; occurs as fine aggregates in cavities in basalts and in some thermally metamorphosed (see CONTACT METAMORPHISM) sandstones.