a volcanic glass that somewhat resembles pitch and has a higher percentage of water than obsidian or other glassy rocks
Origin of pitchstonecalque of German pechstein from pech ( from Classical Latin pix), pitch + stein, stone
Any of various volcanic glasses distinguished by their dull pitchlike luster.
Origin of pitchstoneTranslation of German Pechstein
(usually uncountable, plural pitchstones)