** Shares of Australia's St Barbara SBM.AX fall as much as 36.1% to A$0.195, set for worst trading session since 1990 - if current losses hold

** Stock hits its lowest level since late June

** Gold miner says a huge tax bill has been delivered to it by the Papua New Guinea government related to the firm's Simberi operations

** Says tax bill of A$206.6 mln ($129.02 mln) was delivered to unit Simberi Gold Company

** Simberi Gold intends to lodge a formal and extensive objection within the 60-day objection period

** Stock had risen 45.2% this year, as of last close

($1 = 1.6013 Australian dollars)

(Reporting by Rishav Chatterjee in Bengaluru)

((Rishav.Chatterjee@thomsonreuters.com;))