phonolite

A light-colored volcanic rock composed largely of feldspars.

The name given by Klaproth to certain volcanic rocks of exceedingly variable and complex character, but closely related to the trachytes.

A compact, feldspathic, igneous rock containing nephelite, haüynite, etc. Thin slabs give a ringing sound when struck; — called also clinkstone.

a light-coloured rock of volcanic origin composed mostly of alkali feldspars