Volvanoes make many different types of rocks. For example, black shiny rocks with only a few crystals are usually basalt. The opposite - white shiny rocks with
many crystals and often many bubble holes inside the rock is rhyolite. In between are andesites, which are light gray and usually have large box-shaped crystals
called plagioclase. They come from the Andes Mountains, which is a chain of volcanoes in South America. The Hawaiian islands are mostly made up
of basalts, so they are famous for their beautiful black-sand beaches.