igneous
Granite cobble
Granite (Felsic Plutonic Rock)
Hardness: 6-7 Mohs; Color: Pink, white, and black; Luster: Dull (weathered surface); Texture: Phaneritic (coarsegrained); Composition: Quartz, Potassium Feldspar, and Plagioclase Feldspar with Biotite mica.
- Hardness
- 6-7 Mohs
- Color
- Pink, white, and black
- Luster
- Dull (weathered surface)
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Physical properties
Hardness: 6-7 Mohs; Color: Pink, white, and black; Luster: Dull (weathered surface); Texture: Phaneritic (coarsegrained); Composition: Quartz, Potassium Feldspar, and Plagioclase Feldspar with Biotite mica.
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground. This specific specimen is a rounded cobble, indicating it has been transported and eroded by water or glacial activity.
Uses & applications
In bulk, granite is used for construction aggregate, countertops, and monuments. Smooth cobbles are used in landscaping and decorative masonry.
Geological facts
Granite makes up much of the Earth's continental crust. The pink color in this specimen comes from orthoclase feldspar. Because it is very hard and resistant to weathering, it often survives as river or beach pebbles long after softer rocks have eroded away.
Field identification & locations
Identify by the visible salt-and-pepper or speckled appearance of different mineral crystals. Found globally in mountainous regions and glacial deposits. Common in landscaping rock beds and along riverbanks.
