During an intensive investigation of the joint phenomena of the South Leicestershire igneous intrusions a widened joint cavity eighteen inches long and five wide apparently filled with “calcite or quartz” was noted. On closer examination the mineral showed perfect trapezohedra of analcime and cube-like rhombohedra of chabazite. The analcime crystals attained a diameter of 0·4 inches: they comprised the bulk of the specimen, the chabazite being very subordinate and only in small sizes. As is usual the analcime had preceded the chabazite in order of crystallization. The cubic mineral was colourless, milky white, and also reddish through impregnation with iron oxide. The chabazite was opaque white but translucent on fracture.