Effects of mechanical grinding on the texture and structure of calcium carbonate

Continuous grinding of CaCO3 does not lead to continuous increases in the surface area, but causes it to pass through successive minima and maxima. In spite of its technological significance, this phenomenon has not yet been interpreted.The present work attempts to clarify this problem. We demonstrate that mechanical grinding of CaCO3 leads to successive calcite-aragonite and aragonite-calcite phase transformations; the latter have not been observed before. The mechanism of these phase transformations is explained by a detailed study of the crystalline structures of calcite and aragonite.