If a fragment of rock is incorporated into another rock, it is younger than the surrounding rock.

If a fragment of rock is incorporated into another rock, it is older than the surrounding rock.

If a fragment of rock is incorporated into another rock, it is of no geological significance. 

If a fragment of rock is incorporated into another rock, it is an indication of metamorphosis

If a fragment of rock is incorporated into another rock, it must be the result of a later intrusion.