Pyrite
Image: <a href="//commons.wikimedia.org/wiki/User:Cccefalon" title="User:Cccefalon">CEphoto, Uwe Aranas</a> (CC BY-SA 3.0)
Mineral NamePyrite
Chemical FormulaFeS2
Mohs Hardness6
Crystal Systemcubic
Lustermetallic
Streak Colorgreenish black to brownish black
Cleavageindistinct
Fractureconchoidal
Specific Gravity5
Colorspale brass-yellow, gold, brownish-gray
Transparencyopaque
Type LocalitySparta, Illinois, USA
Mineral GroupSulfides
Usessulfuric acid production, collector specimens, jewelry (historically)
Associated Mineralsquartz, calcite, galena, sphalerite, coal
Raritycommon
Description
This specimen is a pyrite disc, also known as a 'Miners Dollar', exhibiting a radial, flattened form with a metallic luster and a brassy to brownish-gray color. Its surface shows a textured, radiating pattern from the center outwards.
Geological Context
Pyrite forms in a wide range of geological environments, including hydrothermal veins, sedimentary rocks, and metamorphic rocks. Pyrite discs, or 'suns', like this one, are typically found in sedimentary rocks, particularly in coal seams or black shales, where they form through diagenetic processes in anoxic conditions.
