Summary: The constituent manganese minerals of an ore body located at the Lecht mines near Tomintoul include cryptomelane and lithiophorite. The latter, now known to occur extensively in soils, was characterized by X-ray, thermal, and electron microscope techniques. Lithiophorite yields a distinctive differential thermal curve and this was studied in some detail. A platy morphology is revealed under the electron microscope and from selected-area electron diffraction patterns it was concluded that the b parameter of the mineral is 8·73 Å, three times the value determined by Wadsley (1952). As suggested by Wadsley, this could arise from the distribution of lithium ions. Chemical analysis shows that the Lecht lithiophorite is slightly unusual in that it has a high iron and zinc content but is relatively low in cobalt. The associated cryptomelane contains a significant amount of thallium.