igneous
Granite Pebble
Granite (Plutonic Igneous Rock)
Hardness: 6-7 on Mohs scale. Color: Speckled gray, black, pink, and white. Luster: Vitreous to dull. Texture: Phaneritic (medium to coarse-grained mineral grains). Composition: Quartz, feldspar (orthoclase/plagioclase), and biotite or hornblende.
- Hardness
- 6-7 on Mohs scale
- Color
- Speckled gray, black, pink, and white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Speckled gray, black, pink, and white. Luster: Vitreous to dull. Texture: Phaneritic (medium to coarse-grained mineral grains). Composition: Quartz, feldspar (orthoclase/plagioclase), and biotite or hornblende.
Formation & geological history
Formed by the slow crystallization of felsic magma beneath the Earth's surface over millions of years. This particular rounded pebble shape is the result of mechanical erosion and transport by stream, river, or ocean water, which smoothed its outer surface.
Uses & applications
Commonly used in crushed form for road gravel, construction aggregate, and landscaping decor. Larger block specimens are used for countertops, monuments, and building cladding.
Geological facts
Granite makes up a large portion of Earth's continental crust. It is one of the hardest and most durable common stones, often serving as the primary rock in mountain ranges such as the Sierra Nevada and the Himalayas.
Field identification & locations
Look for a distinct 'salt-and-pepper' mottled appearance caused by interlocking grains of glassy quartz, opaque feldspar, and dark biotite or amphibole. Commonly found along riverbeds, beaches, glacial till, and mountainous areas worldwide.
