Call them Pyrite Suns, Pyrite Dollars, Miner’s Dollars, or even Sun Dollars; just don’t call them fossils. They may look like fossilized plants, but the crystal structures actually formed deep underground under great pressure about 350 million years ago. These round disks sometimes occur between seams of coal and may be found when coal is mined. Although pyrite is quite common worldwide, the disk form is virtually unique to Illinois.

Sulfur, which can occur in coal and is a pollutant when burned, occurs in three forms. One of those forms is pyritic sulfur, which occurs as iron sulfide or pyrite (also known as Fool’s Gold). These disks were found at the Conant Mine of Arch Mineral Company located in Conant, Illinois, in Perry County, and near Sparta, Illinois, in Randolph County.