This technique is effective for completely breaking down moderately calcareous to noncalcareous mudstones and shales to produce a concentrated residue of microfossils and non-clay minerals. I have applied this treatment to Mississippian and Pennsylvanian age mudstones and have easily retrieved abundant conodonts, ostracodes, foraminifers, spores, wood fragments, fish teeth, vertebrate bone fragments, silt, mica, pyrite crystals and framboids, and phosphate nodules. All of the above items emerge from the treatment with fine structures such as spines and surface ornamentation undamaged and completely free of surficial clay. This technique is a modification of that of Lund (1970). The chemical used by Lund (Union Carbide Amine 220) is no longer manufactured and an effective alternative is reported here. Furthermore, the additional steps in processing reported here increase the efficacity of the technique for completely dissolving indurated mudstones.