The outer matrices of Thunder Eggs are usually composed of a form of this rock which surrounds the inner core often composed of opal or agate.
The outer matrices of Thunder Eggs are usually composed of a form of this rock which surrounds the inner core often composed of opal or agate. This rock is characterized by phenocrysts of sanidine or alkali feldspar and a fine-grained groundmass of biotite and hornblende as well as plagioclase and quartz. A ghost town in Nevada shares its name with this rock, since it contains many local deposits of this extrusive rock, which is often pinkish in hue and ►has a felsic composition. Commonly found at convergent boundaries and hot spots, FTP, name this extrusive equivalent of granite
The outer matrices of Thunder Eggs are usually composed of a form of this rock which surrounds the inner core often composed of opal or agate.
rhyolite