Pyrite

Hardness: 6-6.5 on Mohs scale. Color: Pale brass-yellow to golden-yellow. Luster: Metallic. Crystal Structure: Typically isometric, commonly forming cubes, octahedra, or pyritohedrons. Often found as massive, granular, or stalactitic forms. Cleavage: None, exhibits conchoidal or uneven fracture. Specific Gravity: 4.95-5.03.

Pyrite forms in a wide variety of geological environments, both igneous, metamorphic, and sedimentary. It commonly forms in sedimentary rocks under anoxic (oxygen-poor) conditions, such as shales and coals. It can also precipitate from hydrothermal fluids in veins, or replace organic material in fossils. Its formation can occur from low to high temperatures and pressures. Geological Age: Pyrite has been forming throughout Earth's history and is found in rocks of all ages, from Precambrian to modern sediments.

Historically, pyrite was used as a source of sulfur for the production of sulfuric acid, and less commonly as an ore for iron. It was also used as a spark producer in early firearms (flintlock mechanisms). Today, its primary uses are for mineral collectors and sometimes as a minor ore for gold when gold is finely disseminated within the pyrite structure. It's occasionally used as an ornamental stone, particularly the well-formed crystals.

Pyrite is often mistaken for gold, which earned it the nickname "fool's gold." This resemblance has led to many false gold rushes throughout history. It can also oxidize to form sulfuric acid, especially when exposed to air and water, which can be an environmental concern in mining areas. Pyrite can sometimes form unique crystal habits, such as the flattened, radial clusters known as 'sun dollars' or 'pyrite suns', typically found in shales.

To identify pyrite in the field, look for its distinctive brass-yellow color and metallic luster. A key test is its hardness: gold is very soft (2.5-3 Mohs) and can be scratched with a knife, whereas pyrite is harder and won't be scratched easily. Pyrite also produces a black to greenish-black streak when rubbed on an unglazed porcelain plate, while gold produces a golden-yellow streak. Pyrite is common worldwide, found in association with many other minerals in various ore deposits, sedimentary basins, and metamorphic rocks. Collectors often seek out well-formed crystals and unique habits like the pyrite suns.