Explains a percentage of the weakness in GDX today because of the weighting http://stockcharts.com/c-sc/sc?s=GG&p=D&b=5&g=0&i=p82497483484&r=1490732059305 and what is this http://blogs.barrons.com/stockstowatchtoday/2017/03/28/why-goldcorp-is-tumbling/