Pietra dell'Etna, from Mt. Etna, Catania, Sicily, Italy
Geological description:
Tuff. Moderately sorted coarse-grained dark crystal-rich ash with rounded grains of plagioclase, pyroxene, olivine, and rarer grains of an opaque oxide mineral. It has an overall basaltic composition, and may be the unaltered equivalent of no. 654.