Granite

Physical Properties

Hardness (Mohs scale): 6-7. Color: Pink to orange-red (potassium feldspar), grey/translucent (quartz), and black (biotite/hornblende). Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained, visible crystals). Specific gravity: 2.63 - 2.75.

Formation & Geological History

Formed through the slow crystallization of magma below Earth's surface (intrusive). The pink/orange hues indicate a high concentration of potassium feldspar. It occurs in continental crust and can date from several billion years to millions of years old.

Uses & Applications

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

Geological Facts

Granite makes up a large part of the continental crust. It is one of the hardest natural stones available, and the radioactive decay within granite can contribute to indoor radon levels in some areas.

Field Identification & Locations

Identify by its 'salt and pepper' appearance with large, interlocking crystals that are clearly visible to the naked eye. It is found globally in large batholiths and mountain ranges like the Sierra Nevada.

Identified on: 4/25/2026

Mode: Standard