igneous
Granite Cobble
Phaneritic Felsic Igneous Rock
Hardness: 6-7 Mohs; Color: Salt-and-pepper (tan, pink, grey) with orange oxidation; Luster: Dull (weathered surface); Texture: Coarse-grained (phaneritic); Cleavage: None for the rock mass.
- Hardness
- 6-7 Mohs
- Color
- Salt-and-pepper (tan, pink, grey) with orange oxidation
- Luster
- Dull (weathered surface)
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Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (tan, pink, grey) with orange oxidation; Luster: Dull (weathered surface); Texture: Coarse-grained (phaneritic); Cleavage: None for the rock mass.
Formation & geological history
Formed through the slow cooling and crystallization of magma deep beneath the Earth's surface (plutonic). This specific specimen shows signs of water erosion (rounding), suggesting it was transported by a river or glacial meltwater.
Uses & applications
Used in landscaping, construction aggregate, and as building stone. Rounded cobbles like this are popular for xeriscaping and garden paths.
Geological facts
Granite is the most common crustal rock on Earth. The visible pink/tan hues are typically from Orthoclase feldspar, while the grey translucent grains are Quartz.
Field identification & locations
Identify in the field by its speckled appearance and extreme hardness (cannot be scratched by a steel blade). Commonly found in riverbeds, glacial moraines, and mountainside scree.
