Two distinct habits are described for redledgeite from the Red Ledge gold mine, California, small black bipyramidal crystals and yellow-green fibres. It is a Ba-Cr-Ti oxide rather than a Mg-Cr-Ti oxide as previously supposed; microprobe analysis gave Ba1.10(Cr1.82Ti5.95Fe0.10V0.08)O16 and Ba1.27(Cr2.48Ti5.49Fe0.02)O16 for the black and yellow-green forms respectively. The mineral is a monoclinic hollandite-type phase, space group I2/m, with a 10.129, b 2.95, c 10.135 A, beta 90.05; Z = 1; D(calc.) for the black form 4.413 g/cm3. The crystal structure was refined to R 6.3% using 1017 reflections; electron diffraction revealed weak superlattice reflections, with a period of 2.24 b due to tunnel cation ordering.-R.A.H.