1) Certain rock fragment 2) Rock 3) Stone 1) Inclusion 
A xenolith (foreign rock) 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 ....
fragment of extraneous rock embedded in magma or another rock
rock fragment within an intrusive igneous body that is unrelated to the igneous body itself. Xenoliths, which represent pieces of older rock ... [2 related articles]
A foreign inclusion in an igneous rock.
A preexisting rock that has been incorporated into magma without melting. When the magma crystallize
a rock fragment that is foreign to the mass in which it is embedded
A piece of rock having a different origin from the igneous rock in which it is found.
[n] - (geology) a piece of rock of different origin from the igneous rock in which it is embedded
noun (geology) a piece of rock of different origin from the igneous rock in which it is embedded
see inclusion
A fragment of country rock enclosed in an intrusive rock.