A
xenolith is a
rock fragment which becomes enveloped in a larger rock during the latter's development and hardening. In
geology, the term
xenolith is almost exclusively used to describe inclusions in
igneous rock during
magma emplacement and eruption. Xenoliths may be engulfed along the margins of a
magma chamber, torn loose from the walls of an erupting
lava conduit or explosive
diatreme or picked up along the base of a flowing body of lava on the Earth's surface. A
xenocryst is an individual foreign crystal included within an igneous body. Examples of xenocrysts are
quartz crystals in a silica-deficient lava and
diamonds within
kimberlite diatremes.