A xenolith is a rock fragment that is captured during the process of magma ascent. The captured rock can be a sedimentary rock, metamorphic rock, or a pre-existing magmatic rock. Xenoliths have irregular shapes, and some are lens shaped. Xenoliths are distributed along the edge of the intruding rock mass, and they can occur alone or in swarms. The long axis of a single xenolith or the direction of a swarm array is usually consistent with the magma flow direction. The edges are often marked by a thermally metamorphosed baked margin.