Dissolution experiments were done on a series of layer-type Mg minerals (brucite, antigorite, talc, and phlogopite) of progressively more complex structure and chemical composition. Twenty-five gram portions of these minerals were dry-ground to <400 mesh and then subjected to controlled dissolution in distilled water at 25°C and 1 atm CO2 partial pressure. For antigorite, talc, and phlogopite, Mg from the octahedral sheets was released more rapidly than was Si from the tetrahedral sheets, i.e., the dissolution was incongruent. It appears that the solubility of these layer-type minerals is related to the relative number of octahedral to tetrahedral sheets present in the structure, i.e., the dissolution kinetics of layer-type silicate minerals is controlled by the rate of destruction of the tetrahedral silica sheets of the mineral.

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