After a short time, the tailings pile can get very large, and can actually block the downstream end of the sluice box.

The problem is that extracting gold from hard rock is often a lot more difficult than processing placer gravels. Still, there is some very high-grade ore out there in many old mining areas.

Now it was time for the nerve-wracking part of the job: actually removing anything from the hanging wall we deemed to be in need of removal because it was either loose, could be loose, looked loose, or we felt it was just downright dangerous

Before going into an analysis of the ore composition, two other major factors will affect the result. These are the accuracy of the assay and the effectiveness of the mill for the gold recovery.