igneous
Granite Pebble
Granite (Plutonic Igneous Rock)
Hardness: 6-7 on Mohs scale. Color: Mottled gray, black, and off-white/pinkish tones. Luster: Dull to vitreous on fresh surfaces. Crystal Structure: Phaneritic (coarse-grained, crystalline interlocking texture). Cleavage: Poor in mass, distinct in individual feldspar grains.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled gray, black, and off-white/pinkish tones
- Luster
- Dull to vitreous on fresh surfaces
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled gray, black, and off-white/pinkish tones. Luster: Dull to vitreous on fresh surfaces. Crystal Structure: Phaneritic (coarse-grained, crystalline interlocking texture). Cleavage: Poor in mass, distinct in individual feldspar grains.
Formation & geological history
Formed from the slow crystallization of silica-rich magma deep underground beneath continental crust. The rounded pebble shape indicates subsequent erosion and transport by stream or glacial water.
Uses & applications
Commonly used in landscaping, river rock decor, aggregate for concrete, architectural stone, and casual rock collecting.
Geological facts
Granite makes up a large portion of Earth's continental crust. Over millions of years, water erosion rounds sharp granite fragments into smooth river pebbles like this specimen.
Field identification & locations
Identify in the field by its speckled, multi-colored pattern consisting of distinct quartz (gray translucent) and feldspar (white/pink) grains with dark mafic minerals (biotite/amphibole). Widely found along riverbeds, beaches, and glacial till worldwide.
