Shortly after the discovery of the mineral kalsilite, the pure potash analogue to nepheline, as a natural mineral occurring in some volcanic ]avas of SW. Uganda by Bannister and Hey, Professor Arthur Holmes suggested that the ncpheline-looking ruineral occurring in a very potash-rich lava at San Venanzo, Umbria, Italy, also might be kalsilitc. His suggestion was based on the high potash : soda ratio of the bulk rock and on the optical properties of the mineral. No X-ray evidence or chemical analysis on the supposed kalsilite has been presented so far.