Pyrite Sun / Miner’s Dollar

Pyrite “suns,” also called “miners’ dollars,” are disk-shaped mineral concretions of pyrite with minor amounts of marcasite. The mineralization pattern of the pyrite suns occurred because the weight of overlying sediment made it easier for crystals to grow laterally (or radially) as opposed to vertically, resulting in flat growth. From Sparta, Illinois, these are found in Pennsylvanian-age rocks, approximately 300 million years old, 200 to 250 feet below ground in coal mines. The disks are found a few inches above the coal seam in thin, pyrite-rich marine “Anna” shale layers in the roof. 

105g/ approx 106mm x 70mm