** Shares of Australia's St Barbara SBM.AX fall as much as 13.6% to A$0.51, their biggest pct fall since June 17
** Gold explorer receives firm commitments to raise A$58 million ($38.38 million) at an issue price of A$0.46 per new share
** Placement price represents 22% discount to co's last close
** Proceeds will be used to accelerate Simberi mobile fleet expansion and conversion, finalising the Simberi expansion feasibility study, others
** SBM up 128.9% YTD
($1 = 1.5113 Australian dollars)
(Reporting by Keshav Singh Chundawat in Bengaluru)
((Keshav.singhchundawat@thomsonreuters.com))