Stamp sand

[1] In the United States, the most well-known deposits of stamp sand are in the Copper Country of the Upper Peninsula of Michigan, where it is black or dark gray, and may contain hazardous concentrations of trace metals.

As mills often relied on steam power to operate and water for some of the processing methods, they were built on the shore of lakes and rivers.

Stamp sand may be hazardous to human health, since it contains trace amounts of harmful heavy metals (such as arsenic).

For this reason, land created from stamp sand may be poisonous to plant life, and can pollute nearby water as well.

In addition, some companies have developed methods to reprocess stamp sands to reclaim their small mineral content.