igneous
Granite Cobble
Granite (Phaneritic Igneous Rock)
Hardness: 6-7 on Mohs scale. Color: Mottled pink, white, and black. Luster: Dull (weathered) to vitreous (on fresh surfaces). Structure: Coarse-grained phaneritic. Cleavage: None (individual minerals have cleavage, but the rock fractures irregularly).
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, white, and black
- Luster
- Dull (weathered) to vitreous (on fresh surfaces)
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled pink, white, and black. Luster: Dull (weathered) to vitreous (on fresh surfaces). Structure: Coarse-grained phaneritic. Cleavage: None (individual minerals have cleavage, but the rock fractures irregularly).
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen has been rounded by fluvial (river) or glacial transport over thousands of years.
Uses & applications
Used extensively in construction (as aggregate), countertops, monuments, and as decorative landscaping stones.
Geological facts
Granite is the primary component of the Earth's continental crust. Because it is resistant to acid rain and very hard, it is the most popular stone for outdoor monuments and headstones.
Field identification & locations
Identify by looking for a 'salt and pepper' appearance with visible crystals of quartz (clear/grey), feldspar (pink/white), and mica (black/shiny). Commonly found in riverbeds and mountainous regions.
