Abstract
Summary: Blebs of anorthoclase-phyric purple rock, usually up to 10 cm but occasionally up to 30 cm in diameter, occur in trachyte lavas of the volcanoes Kilombe and Kapkut, Kenya. The blebs have bulbous outlines and chilled margins and are therefore considered to have been liquid when incorporated in the trachyte. Chemically similar to the benmoreites of Hawaii, Skye and the southern Kenya Rift Valley, they bridge a gap in an otherwise complete sequence of lavas from basalt to trachyte. The failure of benmoreite to erupt as a lava is attributed to viscosity reaching a maximum among intermediate lavas.