igneous
Granite (Weathered)
Grano-diorite / Granite (SiO2 rich intrusive rock)
Hardness: 6-7 Mohs; Color: Speckled tan, grey, and black due to oxidation; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Distinct in feldspars, none in quartz.
- Hardness
- 6-7 Mohs
- Color
- Speckled tan, grey, and black due to oxidation
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Speckled tan, grey, and black due to oxidation; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Distinct in feldspars, none in quartz.
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific sample shows significant surface weathering and iron oxidation (limonite staining), indicating it was exposed to the elements for a long period.
Uses & applications
Used extensively in construction as dimension stone, countertops, road base (crushed), and as architectural veneer.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Because of its hardness, it survives erosion better than surrounding rocks, often forming the cores of major mountain ranges.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and interlocking crystal texture where grains do not rub off like sand. Found worldwide in mountainous regions and shield areas.
