** Australian gold stocks .AXGD fall as much as 5%, set for its worst session since July 9, if trend holds
** Sub-index has lost 2.5% so far in the week; on track to record its worst week since September 19
** Gold prices fell 2% on Thursday, dipping below the $4,000/oz milestone breached for the first time in previous session GOL/
** Shares of gold miners Genesis Minerals GMD.AX fall 6.8%, while those of Northern Star Resources NST.AX and Evolution Mining EVN.AX drop 4.8% and 4.1%%, respectively
** Sub-index has risen 91.5% this year, as of 2317 GMT
(Reporting by Roshan Thomas in Bengaluru)
((Roshan.Thomas@thomsonreuters.com;))