volcanic glass

English Thesaurus

1. a kind of natural glass produced when molten lava cools very rapidly (noun.substance)

hypernym	:	volcanic rock,
definition	:	extrusive igneous rock solidified near or on the surface of the Earth (noun.substance)

hyponym	:	obsidian,
definition	:	acid or granitic glass formed by the rapid cooling of lava without crystallization; usually dark, but transparent in thin pieces (noun.substance)

hyponym	:	pitchstone,
definition	:	dark acid granitic glass (noun.substance)

hyponym	:	tachylite,
definition	:	a basic or basalt glass (noun.substance)