Granite

Physical Properties

Hardness (Mohs scale): 6 to 7. Color: Pinkish-red, white, and black mottled appearance. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained). Composition: Quartz, Potassium Feldspar (yielding the pink/red), and Biotite/Amphibole (the black specks).

Formation & Geological History

Formed through the slow crystallization of magma below the Earth's surface in batholiths. This phaneritic texture develops over millions of years. This specific specimen has been weathered and rounded by water action, likely in a coastal or river environment.

Uses & Applications

Used widely in construction as dimension stone, countertops, monument building, and as crushed aggregate for roads.

Geological Facts

Granite is the most common rock found in the Earth's continental crust. Its pink color is primarily due to an abundance of Alkali (Potassium) Feldspar. The Yosemite Valley in California is made almost entirely of various types of granite.

Field Identification & Locations

Identify in the field by its 'salt and pepper' or mottled appearance with visible, interlocking crystals. Commonly found in mountain ranges or as eroded beach stones. Collectors should look for unique mineral concentrations or large crystal structures.

Identified on: 4/26/2026

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