Xenolith

A xenolith ('foreign rock') is a rock fragment that becomes enveloped in a larger rock during the latter's development and solidification. 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. Xenoliths can be non-uniform within individual locations, even in areas which are spatially limited, e.g. rhyolite-dominated lava of Niijima volcano (Japan) contains two types of gabbroic xenoliths which are of different origin - they were formed in different temperature and pressure conditions.Xenoliths in granodiorite of the Alta Stock, Little Cottonwood Canyon, UtahLarge xenolith of sandstone (probably from the Albee Formation) within the Fairlee Pluton in VermontPeridotite (green) mantle xenolith within a (dark) volcanic bomb from Vulkaneifel, Germany (coin of one euro for scale)Rounded, yellow, weathered peridotite xenolith in a nephelinite lava flow at Kaiserstuhl, SW GermanyLarge xenolith of Baltimore Gneiss in the Guilford Quartz Monzonite in a wall of the old Waltersville Quarry, Granite, Maryland (about 1895)Lamprophyre with xenolith at Ontario, Canada.Xenolith in granite near Donner Pass, California (foot for scale).