Granite

Physical Properties

Hardness: 6-7 on Mohs scale. Color: mottled pink, red, gray, and black. Luster: vitreous to dull. Crystal structure: coarse-grained phaneritic. Cleavage: non-existent (breaks irregularly). Specific gravity: 2.63 - 2.75.

Formation & Geological History

Formed through the slow crystallization of magma below Earth's surface. This specimen shows a high concentration of potassium feldspar (pink/orange) and biotite mica (black streaks). Formation occurs over millions of years in continental crust.

Uses & Applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Also used as crushed stone for road base and railroad ballast.

Geological Facts

Granite makes up the majority of the Earth's continental crust. Because it is so hard and durable, it is often used for curling stones and memorials that need to withstand centuries of weathering.

Field Identification & Locations

Identify in the field by its 'salt and pepper' or multicrystalline appearance where individual mineral grains (quartz, feldspar, mica) are visible to the naked eye. Found globally in mountain ranges and continental shields.

Identified on: 4/21/2026

Mode: Standard