Authigenic minerals play an important role in the preservation of most soft-bodied fossils. The greatest detail is preserved in apatite (calcium phosphate) but its precipitation is usually inhibited by the high concentrations of HCO3- in aqueous settings. Nonetheless, investigations of soft-bodied biotas have revealed very early authigenic calcite crystal bundles in close association with phosphatized soft-tissues. This demonstrates that the geochemical controls on soft-tissue mineralization are dynamic and act on a very local scale. Direct comparisons with experimental results permit the conditions of fossilization to be inferred.