The historic collapse in gold and silver prices on Friday sparked a brutal selloff across mining stocks, as markets aggressively unwound one of January's most crowded trades.As of 2:00 p.m. in New York, silver was down 27% to $84 an ounce, while gold slid 9.5$4,861. Both moves marked the worst single-day declines since 1980 for the two metals.The selloff was just as violent in exchange-traded products tracking precious metals performance. The brutal collapse reflects a sharp repricing of monetary risk ...