During the Fall Semester 2006 the Honors section of Earth Science traveled to Glendon, NC, home of the world famous pyrite collecting location at Standard Mineral Company's pyrophyllite mine. Pyrite is an accessory mineral, as are quartz and fluorite. The mining operation is after the pyrophyllite (Al2Si4O10(OH)2), which is primarily used in the production of ceramics. It is also used as a carrier for agricultural chemicals and as a filler in industrial coatings, sealants and caulks.
No less, people come from all over the world to collect PYRITE (FeS2)...The largest cubes I have seen from this location are about 5 inches in diameter.