igneous
Granite Cobble
Granite (Phaneritic Quartz-Feldspar Felsic Rock)
Hardness: 6-7 on Mohs scale; Color: Pinkish-tan with gray and black specks; Luster: Dull (weathered) to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: None (grains exhibit fracture); Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Pinkish-tan with gray and black specks
- Luster
- Dull (weathered) to vitreous
Identified More igneous →
Explore Granite Cobble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on Mohs scale; Color: Pinkish-tan with gray and black specks; Luster: Dull (weathered) to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: None (grains exhibit fracture); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed through the slow crystallization of silica-rich magma beneath the Earth's surface. High levels of intrusive pressure allow for large mineral crystals. Geological age varies significantly but granite is common in Precambrian to Mesozoic crustal formations. This specific specimen has been further shaped by fluvial or glacial erosion into a smooth cobble.
Uses & applications
Used widely in construction (crushed stone), architecture (countertops, monuments), and dimension stone. Water-worn cobbles like this are often used in landscaping and xeriscaping.
Geological facts
Granite is the primary rock of the Earth's continental crust. Its pink color usually comes from orthoclase feldspar, while the clear/gray glassy parts are quartz and black specks are biotite or hornblende. It is exceptionally resistant to weathering compared to many other rocks.
Field identification & locations
Identify in the field by looking for a 'salt and pepper' appearance with visible crystals (pink, white, and black). Common in riverbeds, glacial tills, and mountain ranges. For collectors, look for unique mineral inclusions or vein patterns.
