igneous
Granite Glacial Erratic
Phaneritic plutonic felsic igneous rock
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white, grey, pink, black); Luster: Dull to vitreous; Structure: Massive, phaneritic (coarse-grained crystals); Composition: Quartz, Feldspar, and Mica.
- Hardness
- 6-7 Mohs
- Color
- Salt-and-pepper (white, grey, pink, black)
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white, grey, pink, black); Luster: Dull to vitreous; Structure: Massive, phaneritic (coarse-grained crystals); Composition: Quartz, Feldspar, and Mica.
Formation & geological history
Formed from the slow cooling of magma deep underground. This specific rounded shape suggests it was weathered and transported by glacial ice or water over thousands of years during the Pleistocene epoch.
Uses & applications
Landscaping, construction aggregate, dimension stone for countertops and monuments, and architectural paving.
Geological facts
Granite is one of the oldest rocks on Earth, making up much of the continental crust. Small inclusions of iron can cause the orange/brown staining (limonite) seen on the surface through oxidation.
Field identification & locations
Identify by its interlocking crystalline texture and lack of layering (foliation). Look for visible grains of translucent quartz and opaque feldspar. Frequently found in regions impacted by past glaciation.
