Pyrite

Hardness: 6-6.5 on Mohs scale. Color: Pale brass-yellow with a greenish tint, often iridescent when tarnished. Luster: Metallic. Crystal Structure: Isometric, typically forming cubes, pyritohedrons, or octahedrons, often striated. Cleavage: Indistinct. Specific Gravity: 4.95-5.10. Has a distinct greenish-black streak.

Pyrite forms in a wide variety of geological environments, including igneous, metamorphic, and sedimentary rocks. It is commonly found in hydrothermal veins, intrusive igneous rocks, sedimentary shales, and coal beds. It can form at high temperatures from magmatic crystallization or at lower temperatures from aqueous solutions. Geological age varies widely depending on the formation context.

Historically, pyrite was used as a source of sulfur for sulfuric acid production and also for striking sparks in early firearms (flintlock mechanisms). Today, it is mainly collected as mineral specimens. While visually similar to gold, it has no direct value as an ore for gold unless gold is present as inclusions within the pyrite itself. It has limited industrial use due to the challenges of extracting iron and sulfur from it efficiently.

Pyrite is commonly known as 'Fool's Gold' due to its superficial resemblance to gold, especially to inexperienced prospectors. It is one of the most common sulfide minerals. When it weathers, it can produce sulfuric acid due to the oxidation of iron sulfide, which can be an environmental concern in mining areas.

To identify pyrite in the field, look for its distinctive brass-yellow color and metallic luster. A key test to differentiate it from gold is its hardness (pyrite is much harder than gold, which is very soft and malleable) and its streak (pyrite has a greenish-black streak, gold has a yellow streak). Pyrite is also brittle, whereas gold is ductile. It can be found globally, often associated with other sulfide minerals, quartz veins, and in sedimentary environments like shales. When collecting, be aware that pyrite can tarnish to darker colors over time due to oxidation.