We have the deepest correction in the current gold bull market stage. It started in early July so we are in the third month of it. While the gold lost only 4.7% of its value (since the top made in early July) GDX lost much more (around 19%). Well, it is called leverage - when gold goes up gold stocks go up much higher...and vice versa.
Now we have the latter case and, in my opinion, it will end when, for example, investors renew the upward trend in gold flows into GLD:
source: Simple Digressions
On the chart above, black lines indicate the periods when gold is flowing out of GLD. Note that during these periods gold prices go down (in this particular case the gold is represented by GLD).
In the current gold cycle we had a similar situation in March and April. Now we have the second, bigger correction.
In my opinion, investors should be patient - the market, especially gold and silver related stocks, went too high and too quickly. As a result, too many weak hands own stocks. When they go away empty handed (as always) another leg up should start.