Last time I did an analysis of this index was on 24/2/2015. There is a slight change in the possible wave counts since then. The long term possible wave counts are shown in the weekly chart below.
Following is the weekly chart of GDX
since septemeber 2011. Since then, the ETF looks like, it is going down
in 5 wave impulse pattern (this 5 wave may be wave C of larger
corrective structure). The current down move, since around USD 21, may
be the final 5th of 5th or it may be the 3rd of 5th (shown in green).
Also an impulse move can keep on extending. But, at the same time, any 5
wave move down may turn out to be the last. Hence, It may be good idea
to open some long positions at the completion of any 5 wave down move
(time frame daily). If the up move afterwards turns out be corrective,
then exit those long positions taken earlier.