igneous
Granite
Phaneritic Plutonic Felsic Rock
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).
- Color
- Pinkish-red, white, and black mottled appearance
- Luster
- Vitreous to dull
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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.
