Three Mn minerals (Mn content 77.0-93.5%) were analyzed for chem. compn. and structure (ay. pore size 52-58 angstrom) and used as catalysts for decompn. of H(2)O(2) at room temp. and oxidn. of PhOH in aq. soln. at 20-70 degrees C. The H(2)O(2) decompn. rate increased with increasing Mn content in the catalyst. The conversion of PhOH increased with increasing temp. of oxidn. but did not depend on the H(2)O(2) concn.