Pyrite Dollar (Pyrite Sun)
Formed in the seams between black shale and coal 300,000,000 years ago, these pyrite dollars do not appear to be fossils, but an aggregate of tiny pyrite crystals.
Today, they are collected by coal miners in Randolph County, Illinois. As the Illinois coal mines are shut down one by one, these specimens will become more and more rare.
Chemistry: Iron Sulfide ♦ Class: Sulfides ♦ Color: brass-yellow ♦ Luster: metallic ♦ Transparency: opaque ♦ Fracture: none/conchoidal ♦ Crystal system: Isometric ♦ Moh's hardness: 6-6.5 ♦ Localities: Sparta, Randolph Co. Illinois