Pyrite
Sometimes called IRON PYRITE, or FOOL'S GOLD, a naturally occurring iron disulfide mineral. The name comes from the Greek word pyr, "fire," because pyrite emits sparks when struck by steel. Nodules of pyrite have been found in prehistoric burial mounds, which suggests their use as a means of producing fire. Pyrite is called fool's gold because its color may deceive the novice into thinking he has discovered a gold nugget.
Pure pyrite (FeS2) contains 46.67 percent iron and 53.33 percent sulfur; its crystals display isometric symmetry. Pyrite is widely distributed and forms under extremely varied conditions. For example, it can be produced by magmatic (molten rock) segregation, by hydrothermal solutions, and as stalactitic growth. It occurs as an accessory mineral in igneous rocks, in vein deposits with quartz and sulfide minerals, and in sedimentary rocks, such as shale, coal, and limestone.
Pyrite occurs in large deposits in contact metamorphic rocks. Deposits of copper-bearing pyrite are widely distributed and often of great size. They usually occur in or near the contact of eruptive rocks with schists or slates. Pyrite weathers rapidly to hydrated iron oxide, goethite, or limonite. This weathering produces a characteristic yellow-brown stain or coating, such as on rusty quartz.
Pyrite is used commercially as a source of sulfur, particularly for the production of sulfuric acid. Because of the availability of much better sources of iron, pyrite is not generally used as an iron ore.
For many years Spain was the largest producer, the large deposits located on the Tinto River being important also for copper. Other important producers are Japan, the United States (Tennessee, Virginia, California), Canada, Italy, Norway, Portugal, and Slovakia.