Abstract: Rectangular parallelopipedic lepidocrocite particles of the present invention have a minor axial diameter of 0.045 to 0.5 .mu.m, a major axial diameter of 0.05 to 1.0 .mu.m, and a thickness of 0.001 to 0.3 .mu.m, which are individual. Such rectangular parallelopipedic lepidocrocite particles according to the present invention are firstly used as a coloring pigment for paints, resin moldings, printing ink, road asphalt, cosmetics, etc., and secondly used as a non-magnetic material for non-magnetic undercoat layers which are formed on non-magnetic substrates which constitute a substrate for magnetic recording media, and which have an excellent surface smoothness and a high strength.