#aphanite

• Aphanite — An igneous rock (volcanic or subvolcanic) featuring an extremely fine-grained, microcrystalline, or glassy texture, where the component crystals are so small that they cannot be distinguished with the naked eye, requiring an optical microscope for identification. As an adjective, it describes the specific texture of these rocks (such as basalt or andesite), resulting from the rapid cooling of magma at the Earth's surface.