KNOOP MICROHARDNESS ANISOTROPY OF SINGLE-CRYSTAL ARAGONITE

The Knoop microhardness was measured for indentation test loads from 25 to 200 g on the (100), (010), and (001) planes of single-crystal aragonite (nonbiogenic). Although the microhardness of this aragonite is quite anisotropic on the (100) and (010), it is nearly isotropic on the (001) plane. The microhardness profiles are discussed relative to the structure of aragonite, and the hardnesses are compared with those which have been determined for calcite on its cleavage plane. The indentation load/size effect (ISE) is addressed for aragonite and compared with that of calcite on its cleavage plane.