Granite

Hardness: 6-7 (Mohs scale), Color: Varies widely, often white, pink, gray, or black due to mineral composition; speckled appearance. Luster: Vitreous to sub-vitreous. Crystal Structure: Phaneritic (coarse-grained) texture, interlocking crystals. Cleavage: Poor to non-existent. Specific Gravity: 2.6-2.7 g/cm³.

Formed from the slow crystallization of magma below the Earth's surface. It's an intrusive igneous rock, meaning it cooled and solidified within the Earth's crust. This slow cooling allows for the formation of large, easily visible crystals. It typically forms in continental crust settings where tectonic plate collisions or subduction zones lead to the melting of pre-existing rocks. Geological age varies greatly, from Precambrian to Cenozoic, depending on the specific intrusion event.

Industry/Construction: Widely used as a building material (countertops, flooring, paving stones, curbing), monumental stone, and in civil engineering projects due to its durability, strength, and aesthetic appeal. Jewelry: Rarely used as a gemstone itself, but polished slabs can be incorporated into decorative items. Other: Tombstones and memorials.

Granite is one of the most abundant igneous rocks in the Earth's continental crust. It is often associated with the formation of mountain ranges. The term 'granite' actually encompasses a range of similar rocks with varying proportions of quartz, feldspar, and mica. The name comes from the Latin 'granum', meaning 'grain', in reference to its coarse-grained structure.

To identify in the field: Look for its coarse-grained texture, composed of interlocking crystals that are typically visible to the naked eye. The presence of clear to milky quartz, white or pinkish feldspar, and darker minerals like biotite or hornblende is characteristic. It is a hard rock, difficult to scratch with a knife. Common locations: Found worldwide, forming the core of many mountain ranges and large batholiths. Significant occurrences include the Sierra Nevada Batholith (USA), the Brazilian Shield, parts of Scandinavia, and various locations in India and China. Tips for collectors: Granite is very common, so focus on collecting aesthetically pleasing or unusually colored specimens. Observing the relative proportions and sizes of the constituent minerals can be interesting.