Stamp sand Wikipedia
Stamp sand, photographed near Houghton, MI. Stamp sand is a coarse sand left over from the processing of ore in a stamp mill. In the United States, the most wellknown deposits of stamp sand are in the Copper Country of northern Michigan, where it is black or dark gray, and may contain hazardous concentrations of trace metals.. In the 19th and early 20th centuries, many metal mines used stamp ...