arsoite
noun
ar·so·ite
ˈär(ˌ)sōˌīt
plural -s
: 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
Word History
Etymology
German arsoit, from Arso, town on the island of Ischia, Italy + German -it -ite