Gold prices are at record highs. But disappointing results at the world's largest miner of the yellow metal signals companies may be struggling to take full advantage of sizzling demand. Newmont Corp. shares posted their biggest daily drop since 1997 on Thursday, tumbling 15% after the Denver-based company posted earnings, revenue and profit margins that fell short of analysts' estimates in the third quarter, dragged down by higher costs. The stock traded a further 3% lower on Friday, with top rivals Barrick Gold Corp. and Agnico Eagle Mines Ltd. also retreating.