The mechanical properties of powders at high pressures are difficult to measure and therefore such data are rarely reported in open literature. Available test equipment mainly operates in the low-pressure region, 0-200 MPa. Calcite (CaCO3) is a mineral suitable for high-pressure processes, e.g. sintering of diamond compacts. It is also a very common material in the earth core and therefore of interest for geoscientists. In order to model the processes in the high-pressure region (above 1 GPa), knowledge of the mechanical properties of the powder in the entire pressure range is needed. Experimental studies have been conducted to investigate the pressure-density relationship of a CaCO3 powder and also to correlate the relative density to elastic and strength properties using experimental results. Further, a methodology has been introduced to provide a foundation for an elastic-plastic constitutive model. The mechanical behaviour of a CaCO3 powder mix has been investigated using the Brazilian disc test, uniaxial compression testing and closed die experiments. The experiments showed increasing elastic modulus and strength with increasing density. An empirical expression of the dependence of the bulk modulus on density has also been introduced. (C) 2010 Elsevier B.V. All rights reserved.