Hundreds of breccia pipes, some mineralized with ore-grade Cu and/or U, occur in the Colorado Plateau of N Arizona. The pipes originated in the Mississippian Redwall limestone, on its solution-collapse, and stoped through the overlying strata to the Triassic Chinle formation. Mineralization occurred during the Mesozoic, first with Mississippi Valley-type Cu-Pb-Zn deposits, and later with uraninite. The origin of the mineralizing fluids is unknown. Prospecting criteria and the complete systematics of these pipes and their mineralizations require further research.-G.J.N.