Berkelium is a synthetic element. It doesn't occur in nature because of its instability, so must be made in a laboratory. Discovered by Stanley G. Thompson, Albert Ghiorso, Glenn T. Seaborg, Kenneth...
Stanley G. Thompson, Albert Ghiorso, Glenn T. Seaborg, Kenneth Street - December 1949, Berkeley Laboratory, University of California. The nuclear reaction is: 24195Am + 42He → 24397Bk + 2 1n