Granite

Physical Properties

Hardness: 6-7 on Mohs scale; Color: typically mottled pink, white, gray, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) interlocking crystals; Cleavage: none (minerals within have cleavage, the rock fractures irregularly).

Formation & Geological History

Formed through the slow crystallization of magma below Earth's surface (intrusive). They are found in continental crust and are typically associated with mountain-building processes and ancient batholiths.

Uses & Applications

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

Geological Facts

Granite is the most common igneous rock found at Earth's surface. It makes up much of the continental crust. Half Dome in Yosemite National Park is one of the world's most famous granite monoliths.

Field Identification & Locations

Identify by its 'salt and pepper' appearance and visible interlocking crystals of different colors. It is found in large outcrops or as river-worn stones in mountainous regions. Tips for collectors: look for sharp crystal boundaries and high hardness (it will scratch glass).

Identified on: 5/2/2026

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