ˈrīəˌlīt noun
( -s )
Etymology: German rhyolith, from rhyo- (irregular from Greek rhyak-, rhyax stream of lava) + -lith -lite — more at rhyacolite
: a very acid volcanic rock that consists typically of phenocrysts of quartz, sanidine, and sometimes oligoclase embedded in a groundmass of minute crystals usually mixed with glass and is the lava form of granite
• rhy·o·lit·ic |rīə|lid.ik adjective