HOLLYWOOD — Diamonds may be a girl’s best friend, but Leonardo DiCaprio, Djimon Hounsou and Jennifer Connolly were the shiniest gems Dec. 6 at the preem of Ed Zwick‘s actioner “Blood Diamond.”

Warners turned the evening — after-preem party was at the Roosevelt Hotel across from Grauman’s Chinese — into a benefit for watchdog orgs Global Witness and Amnesty Intl., who have led the fight to stop the sales of blood, or conflict, diamonds.

“This is an important movie,” said Graham King, one of the producers of the pic. “It’s entertaining and it sends a message.”

That message is exactly what the powerful diamond biz is worried about. Trade group the World Diamond Council, which hired spin doc Allan Mayer, says it has fully supported the Kimberley Process, which requires that diamonds are subject to a strict certification.