Pyrite

Hardness: 6-6.5 on Mohs scale. Color: Pale brass-yellow to golden. Luster: Metallic, often bright. Crystal Structure: Isometric (cubes, octahedrons, pyritohedrons) or massive, granular, stalactitic. Cleavage: Indistinct. Specific Gravity: 4.95-5.10. Streak: Greenish-black.

Pyrite forms in a wide variety of geological environments. It can be found as an accessory mineral in igneous rocks, in hydrothermal veins (often with other sulfide minerals), in sedimentary rocks (formed in anoxic conditions), and in metamorphic rocks. Its formation often involves the presence of iron and sulfur-rich fluids reacting with organic matter or other minerals. Geological Age: Pyrite has formed throughout Earth's history and can be found in rocks of almost any age.

Historically, pyrite was sometimes mistaken for gold, leading to its nickname 'Fool's Gold.' Today, it is a significant source of sulfur for the production of sulfuric acid, which is widely used in various industries. It can also be a minor ore of iron, though not as important as hematite or magnetite. In jewelry, polished pyrite can be used for cabochons or small ornamental pieces. It is also a popular specimen for mineral collectors due to its distinctive metallic luster and crystal forms.

Pyrite's name comes from the Greek word 'pyr,' meaning 'fire,' because it produces sparks when struck by metal. This property was utilized by early civilizations for starting fires. It is also known to oxidize when exposed to air and moisture, producing sulfuric acid, which can be an environmental concern in mining areas (acid mine drainage).

In the field, pyrite is easily identified by its distinctive metallic, brassy-yellow color, typically blocky or cubic crystal habits, and its hardness (it cannot be scratched with a knife blade, unlike real gold). It is much harder and more brittle than gold. Common locations include Spain (Navajún, famous for perfect cubes), Peru, the United States (various localities, including Colorado and Arizona), and parts of Europe, Africa, and Asia. Collectors often look for well-formed crystals, particularly cubes and pyritohedrons, or specimens associated with other minerals.