Only the richest ores could be worked and shipped off for processing at a profit. As a result, early mining in the southern part of the Humboldt Range was short-lived. In the 1880s, placers were discovered in Spring Valley and American Valley on the east side of the range...

Common thought is the switchback slows the velocity of the rushing water and gold drops out from the cut bank to a fill gravel bar within or below the switchback. I am not going to disregard that model; however, I hope to improve upon it.

How rich does a hard rock ore have to be for it to be worthwhile to process and extract the gold?

For the prospector, knowing what oxidized hydrothermal alteration looks like in the field is an important exploration tool.