** Polymetals Resources POL.AX rises as much as 7.6% to A$0.775; marks biggest intraday pct gain since June 26
** Miner says Endeavor silver-zinc mine in New South Wales has covered operating costs within first full month of production
** Exec Chairman Dave Sproule says, "With operations now self-sustaining, the focus shifts to optimising both mining and milling performance"
** POL last up 5.6%, trims YTD losses to 4.4%
(Reporting by Kumar Tanishk in Bengaluru)
((Tanishk.Kumar@thomsonreuters.com; X: @thatstanishk;))