Magnesian Calcites in Urinary Stones of Herbivorous Mammals

Calcite is the most frequent component of urinary stones in herbivorous mammals (Grunberg, 1964). Chemical and X-ray diffractometric analyses show that regularly up to 20 mole% magnesium carbonate is found in the calcite lattice. Due to the statistical distribution of the Mg ions the lattice constants of the calcite are reduced and the diffraction angles are correspondingly increased. This is clearly seen in the position of the strongest reflection of calcite (104). According to Chave (1952) and Goldsmith and Graf (1958) there is a linear dependence between the (104) interplanar spacing and the amount of MgCO3 in calcite. This relationship is also applicable to magnesian calcite stones in mammals (Fig. 1).