Noun
a grey volcanic rock containing plagioclase and quartz and other crystalline minerals
Source: WordNetMammoth Mountain is a lava dome complex in the southwestern corner of the caldera, consisting of about 12 rhyodacite and dacite overlapping domes. Source: Internet
The largest of the dacite domes formed the previous summit, and off its northern flank sat the smaller Goat Rocks dome. Source: Internet
The mountain includes layers of basalt and andesite through which several domes of dacite lava have erupted. Source: Internet