Summary: Spherulitic and felted green to brown minerals are described from various volcanic rocks of the Western Ochils, Stirlingshire. They fill amygdales and replace pyroxenes and appear to be an interlayered series of sheet silicates from celadonite to vermiculite. The minerals are hydrothermal in origin and suggest the presence of a potassium-rich hydrous fluid at a late stage in the volcanic history.