** Shares of Blackstone Minerals BSX.AX fall as much as 11.9% to A$0.080, their lowest levels since June 24

** Stock set for worst day since May 19, if trends sustain

** The nickel sulphide explorer secures A$22.6 million ($14.8 million) for major drill programme at Mankayan copper-gold project in the Philippines

** Issue price of A$0.078 per share represents a 14.3% discount to last close

** YTD, BSX gains 192.9%, including the session's moves

($1 = 1.5230 Australian dollars)

(Reporting by Keshav Singh Chundawat in Bengaluru)

((Keshav.SinghChundawat@thomsonreuters.com))