One fall evening in 1881, a prospector named Henry Spiller knocked on the door of Aaron and Rosie Winters’ modest stone cabin about 40 miles due east of Death Valley and asked to stay the night.

After dinner Spiller exuberantly showed off a sample of “cotton ball,” a weird, semi-translucent rock formation containing borax. Spiller suggested to his hosts that fortunes awaited those lucky enough to find a generous deposit of the stuff. He showed them how to test for …