Granite

Hardness: 6-7 (Mohs scale), Color: Typically reddish-pink due to potassium feldspar, but can vary (grey, white, black, green). Luster: Vitreous to greasy. Crystal Structure: Granular, phaneritic (visible crystals). No distinct cleavage; irregular fracture. Specific Gravity: 2.6-2.7 g/cm³.

Formed from the slow crystallization of magma below Earth's surface (intrusive igneous). It cools slowly, allowing large crystals to form. Its geological age varies widely, from Precambrian (billions of years old) to Cenozoic, depending on the specific intrusion. It forms in continental crust settings, often associated with orogenic (mountain-building) events and subduction zones.

Industry: Countertops, flooring, building facades, tombstones, cobblestones. Construction: Crushed for road aggregate, concrete, and asphalt. Jewelry: Not typically used as a gemstone due to its opacity and composite nature, but polished slabs can be appreciated for their aesthetic patterns. It's often used ornamentally.

Granite is one of the most common igneous rocks on Earth. Its name comes from the Latin 'granum', meaning 'grain', in reference to its coarse-grained structure. It is often associated with mountain building and is found in the cores of continents. Many famous monuments and buildings, such as Mount Rushmore and the Egyptian pyramids, use granite.

Field Identification: Look for a coarse-grained texture with interlocking crystals. The presence of pink/red (potassium feldspar), white/grey (plagioclase feldspar), glassy grey (quartz), and black flecks (biotite/amphibole) is characteristic. Its overall color and appearance can vary. Common Locations: Found in continental shield areas, mountain ranges, and batholiths worldwide (e.g., Sierra Nevada in California, Appalachian Mountains, Scandinavian Shield, Indian Shield). Tips for Collectors: River-worn granite pebbles, like the one pictured, are common and can be easily identified by their rounded shape and characteristic mineral composition.