Granite

Physical Properties

Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (white, pink, and black). Luster: Vitreous to dull. Crystal structure: Phaneritic (coarsegrained visible crystals). Cleavage: Varies by mineral (perfect on mica, good on feldspar). Specific gravity: 2.63 to 2.75.

Formation & Geological History

Formed through the slow crystallization of magma below Earth's surface (plutonic). It is primarily composed of quartz, feldspar, and plagioclase with minor amounts of mica and amphiboles. Found in continental crust throughout all geological ages.

Uses & Applications

Used extensively in construction for countertops, floor tiles, paving stones, curbing, and monuments/gravestones due to its durability and aesthetic appeal.

Geological Facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. It is one of the hardest natural substances on Earth.

Field Identification & Locations

Identify in the field by its interlocking 'mosaic' texture of visible light-colored quartz/feldspar and dark biotite/hornblende crystals. Common in mountain ranges and eroded shield areas. It will not be scratched by a steel knife.

Identified on: 4/22/2026

Mode: Standard