Algal borings are responsible for the development of micrite envelopes, and high Mg calcite may be present in these borings and other void spaces within aragonite grains. In these cases, the presence of the two minerals furnishes the solubility contrast necessary for the preservation of textural features in the face of massive solution. The earliest and most rapid change in the diagenesis of such a carbonate sediment is the stabilization of high Mg calcite as low Mg calcite. Simultaneously or later, aragonite may undergo solution, leaving behind a fine network of the less soluble low Mg calcite which is pseudomorphic after high Mg calcite. This network is essentially a skeleton of the original texture of the sediment and serves as a mold and nucleation site for later infilling by calcite.