Granite (weathered/river-tumbled)

Hardness: 6-7 on Mohs scale (due to quartz and feldspar). Color: Varies widely; often pink, red, gray, or white, with dark mineral specks. Luster: Vitreous to dull. Crystal Structure: Phaneritic (coarse-grained), interlocking crystals. Cleavage: Feldspar shows good cleavage, quartz does not. Specific Gravity: 2.65 - 2.75.

Formed from the slow crystallization of magma below the Earth's surface. This slow cooling allows for the formation of large, interlocking mineral grains. Granites typically form in continental collision zones or during the formation of mountain ranges. Geological Age: Ranges from Precambrian to Cenozoic; its formation is an ongoing process in areas of active mountain building.

Industry/Construction: Widely used as a construction material (dimension stone) for countertops, flooring, curbing, building facades, and monuments due to its hardness, durability, and aesthetic appeal. It is also crushed for road aggregate. Jewelry: Though not typically used for jewelry itself, polished granite can be used in decorative items. Collecting: Commonly collected by enthusiasts due to its varied appearance and prevalence.

Granite is one of the most abundant igneous rocks in the Earth's continental crust. Many famous monuments and buildings, such as Mount Rushmore, are carved from or built with granite. 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 feldspar-rich igneous rocks.

To identify in the field: Look for interlocking, coarse-grained crystals of quartz (glassy, grey/clear), feldspar (pink, white, or orange), and darker minerals (like biotite or hornblende, appearing as black specks). The specimen in the image appears to be a river-tumbled or weathered piece of granite, hence its rounded shape and somewhat muted colors compared to a fresh break. Common locations: Found worldwide in mountainous regions, continental shields, and batholiths. Significant occurrences include the Sierra Nevada mountains in California, Stone Mountain in Georgia, the Scottish Highlands, and parts of Scandinavia and Brazil. Tips for collectors: Look for fresh exposures to see true colors and crystal shapes. Weathered samples like this one demonstrate the effects of erosion and transportation.