A technique for leaching rock specimens with acid has been developed for the investigation of the magnetic properties of red sediments. The efficiency of the leaching depends strongly on the shape of the specimen, and cylindrical specimens with an axial hole were found to be the most suitable, both for the leaching process and for subsequent magnetic measurements. Applying the technique to Carboniferous red sandstones from the Maritime Provinces, two magnetic components were separated and identified with red and black constituents. The red magnetic component has higher blocking temperatures and coercivities than the black, and is more resistant to alternating field demagnetization. An earlier explanation of the magnetization of these red beds requires some modification.