Knoop microhardness anisotropy on the cleavage plane of single crystals with the calcite structure

Abstract

Knoop microhardness profiles were determined on the (1011) cleavage planes for a series of natural rhombohedral carbonate single crystals, including calcite, magnesite, rhodochrosite, siderite, smithsonite, and the structurally related dolomite. Indentation test loads of 25 g, 50 g, 100 g, and 200 g were utilized. The resulting deformation features were examined using scanning electron microscopy (SEM). Twinning was observed in the calcite sample only. The physical properties of the other carbonate samples were considered to account for their deformation.