Berynium was a type of valuable mineral substance.
History and specifics[]
Deposits of berynium (along with dilithium, duranium and dolacite) were found on the planet Beta Cabrini IV, home to a Federation colony. As such, the minerals were the reason the colony was attacked by Merkaan raiders led by Hamesaad Dreen in the year 2268. (TOS novel: Legacy)