Compression of calcite to 40 KB

The compressibility of calcite to 40 kbar has been remeasured by using a piston-cylinder apparatus. Calcite 1 is found to transform to calcite 2 at 14.5 kbar with a volume change of 0.00483 cm3/g, and calcite 2 is found to change to calcite 3 at 17.4 kbar with a volume change of 0.01291 cm3/g. The volume compression data for the three phases are described by the following quadratic relations: Calcite 1 Calcite 2 Calcite 3 where P is pressure in kilobars. The compression data for calcite 1 and calcite 3 are in good agreement with those available in the literature. The data exhibiting an abnormally high compression of calcite 2 have been reported for the first time. The compression data for calcite 2 have been used to explain quantitatively the abnormal drop near 15 kbar observed in the ultrasonic sound velocity in calcite.