In the precious metals complex, that would be the HUI Gold Bugs index. With a low today (so far) of 229.15 the upper bound of the 220 to 230 target zone has been struck.
If we assume that zone is a good target (and a tick below 28 for GDX is a good target) and if we assume the macro fundamentals will be in place (needing a broad stock market weakening vs. gold, the yield curve to stop inverting, and other signals to stay in line and/or improve) then it is time to be on buyers’ alert. There is likely lower to go (e.g. GDX gap fill below 28) but technically, the bulk of the correction in price is in if we assume (another assumption!) that the sector is going to generally make higher lows at the March lows (some items have doinked below it).