Granite

Hardness: 6-7 (Mohs scale) due to quartz and feldspar content. Color: Predominantly reddish due to potassium feldspar (orthoclase), with lighter grey/white (plagioclase, quartz) and dark speckles (biotite, hornblende). Luster: Vitreous to sub-vitreous. Crystal structure: Phaneritic (visible interlocking crystals), typically equigranular. No true cleavage as it's a rock, but individual mineral components have cleavage (e.g., feldspar, biotite). Specific gravity: 2.6-2.7.

Granite forms from the slow crystallization of magma beneath the Earth's surface. It's an intrusive igneous rock, meaning the magma cools and solidifies before reaching the surface. This slow cooling allows large, interlocking mineral crystals to form. It typically forms in orogenic belts (mountain-building events) and continental collision zones, often associated with subduction zones. Its geological age varies widely depending on the specific intrusion, ranging from Precambrian to Cenozoic.

Industry/Construction: Widely used as a building stone (dimension stone) for floors, countertops, wall cladding, and monuments due to its hardness, durability, and aesthetic appeal. Jewelry/Decorative: Polished granite slabs are popular for decorative purposes. Crushed granite is used as aggregate in road construction and concrete. Art: Used for sculptures and carvings.

Granite is one of the most abundant igneous rocks in the Earth's continental crust. Several famous landmarks and structures are made of granite, including Mount Rushmore, the pyramids of ancient Egypt (some components), and many cathedrals and government buildings worldwide. It's often associated with mountainous regions and the cores of continents. The term 'granite' is often used broadly in commercial settings to include other similar-looking felsic intrusive rocks.

To identify granite in the field, look for its characteristic speckled appearance with visible interlocking crystals (phaneritic texture). The presence of pink/red (potassium feldspar), white/grey (plagioclase feldspar and quartz), and black (biotite mica or hornblende) minerals is key. It's a very hard rock, difficult to scratch with a knife. Commonly found in large batholiths and plutons in continental crust, exposed in eroded mountain ranges, quarries, and glacial deposits. For collectors, well-formed samples showing distinct mineral grains are desirable; polished slabs showcase its beauty best. Rounded, smooth pieces like the one pictured often indicate it has been tumbled by water (e.g., by a river or glacier).