Delessite is of much rarer occurrence in Scotland than saponite, and moreover it is by no means so characteristic in its appearances. Its modes of occurrence are much the same, only it is much less frequently the tenant of drases, affecting rather rents or fissures, and in these last it frequently goes to form what may be called a " composite vein." This may be filled for the most pȧrt with fibrous calcite, transversely disposed, and the reopening of the fissure is disclosed by the delessite, which, after lining one side of the vein for some distance, suddenly crosses the fibres of the calcite diagonally, and lies between i~ and the rock upon the opposite side.