igneous
Granite Cobble
Granite (composed primarily of Quartz, Alkali Feldspar, and Plagioclase)
Hardness: 6-7 Mohs; Color: Salt and pepper/grey; Luster: Phaneritic (crystalline/dull); Crystal Structure: Granular; Specific Gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper/grey
- Luster
- Phaneritic (crystalline/dull)
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper/grey; Luster: Phaneritic (crystalline/dull); Crystal Structure: Granular; Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep beneath the Earth's surface (plutonic). This specimen has been rounded by fluvial processes (river/water erosion) into a cobble shape. Age can range from millions to billions of years.
Uses & applications
Commonly used in construction as crushed stone, dimension stone for countertops, and in landscaping. Polished granite cobbles are used for decorative paths and aquarium features.
Geological facts
Granite is the primary rock composing the Earth's continental crust. Its name comes from the Latin word 'granum', meaning a grain, in reference to its coarse-grained structure.
Field identification & locations
Identify in the field by its visible interlocking crystals of quartz and feldspar and its extreme hardness. It won't be scratched by a steel knife. Commonly found in riverbeds and mountainous glaciated regions.
