igneous
Granite Pebble
Granite (plutonic felsic intrusive rock)
Hardness: 6-7 Mohs scale. Color: Off-white, tan, reddish-brown with dark speckles. Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained coarse crystalline interlocking texture). Specific gravity: ~2.6-2.7. Primarily composed of quartz, potassium feldspar, plagioclase feldspar, and biotite mica or hornblende.
- Hardness
- 6-7 Mohs scale
- Color
- Off-white, tan, reddish-brown with dark speckles
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs scale. Color: Off-white, tan, reddish-brown with dark speckles. Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained coarse crystalline interlocking texture). Specific gravity: ~2.6-2.7. Primarily composed of quartz, potassium feldspar, plagioclase feldspar, and biotite mica or hornblende.
Formation & geological history
Formed deep beneath the Earth's surface through the slow cooling and crystallization of silica-rich felsic magma. This specific specimen exhibits a rounded, weathered surface typical of alluvial or glacial erosion.
Uses & applications
Used extensively in construction as crushed stone, dimension stone, building facades, and countertops. Rounded stream pebbles are used in landscaping, aquariums, and rock tumbling.
Geological facts
Granite makes up a major part of the continental crust. The term granite comes from the Latin word 'granum', meaning a grain, referring to its coarse-grained structure.
Field identification & locations
Identified by its salt-and-pepper speckled appearance and intergrown visible crystals of translucent quartz, opaque white/pink feldspar, and dark biotite or amphibole. Commonly found along riverbeds, beaches, and in mountain ranges globally.
