igneous
Granite Pebble
Granite (Phaneritic intrusive igneous rock)
Hardness: 6-7 on Mohs scale; Color: Mottled grey, pink, and black; Luster: Dull to vitreous; Crystal structure: Coarse-grained (phaneritic); Cleavage: Dependent on individual mineral grains; Specific gravity: approx. 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled grey, pink, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled grey, pink, and black; Luster: Dull to vitreous; Crystal structure: Coarse-grained (phaneritic); Cleavage: Dependent on individual mineral grains; Specific gravity: approx. 2.63 to 2.75.
Formation & geological history
Formed from the slow cooling of magma deep beneath the Earth's surface (plutonic). This specific specimen has been rounded by fluvial (river) or glacial transport, likely during the Quaternary period.
Uses & applications
Used primarily as construction aggregate, dimension stone for countertops and monuments, and in landscaping. Smaller pebbles are often used in decorative gravel or as river rock for drainage.
Geological facts
Granite makes up much of the Earth's continental crust. Over 80% of the Earth's volume is composed of igneous rocks, with granite being the most common intrusive type. The red/pink hues come from potassium feldspar.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals of quartz (clear/grey), feldspar (white/pink), and mica (black). Commonly found in stream beds or glacial till near mountain ranges.
