Volcanic breccias are clastic-textured, extrusive igneous rocks. They generally appear as multicolored masses of jumbled angular grains. Volcanic breccias have violent origins. They form from explosive volcanic eruptions (cf. effusive eruptions - lava flow eruptions). Volcanoes having felsic or intermediate chemistries typically erupt violently. Powerful volcanic ash eruptions result in deposits with mixes of large & small grains. Upon burial & lithification, these deposits become volcanic breccias.
The clastic texture of volcanic breccia is often termed pyroclastic or volcaniclastic.
Volcanic breccia from Mexico with clasts of jelly opal (= dark orangish-red pieces).