1. A fine-grained volcanic rock of intermediate composition, typically dark gray or black, formed from lava that cools rapidly.
Usage: geology; technical

Examples

• Andesite is commonly found in volcanic regions around the Pacific Ring of Fire.
• The mountain's slopes were composed largely of andesite lava flows.
• Geologists identified andesite samples from the volcanic eruption.
• Andesite differs from basalt in having a lower iron and magnesium content.
• The dark andesite rock was used as a building material in the ancient city.