arsoite

\\ˈär(ˌ)sōˌīt\ noun (-s)

Etymology: German arsoit, from Arso, town on the island of Ischia, Italy + German -it -ite

: a dark gray porous rock consisting of trachyandesite containing phenocrysts of andesine, sanidine, diopside, and a little olivine in a trachytic groundmass of sanidine, a little oligoclase, much diopside, and magnetite