Dec 17 (Reuters) - Black Rock Mining Ltd BKT.AX :
* POSCO TO INVEST USD$7.5M TO ACQUIRE 15% OF BLACK ROCK-BKT.AX
* TO ISSUE A TOTAL OF 126 MILLION SHARES AT ISSUE PRICE OF A$0.082 PER SHARE
* CO & POSCO TO FINALISE LONG-FORM OFFTAKE & PREPAYMENT AGREEMENT