igneous
Granite Cobble
Plutonic Granite
Hardness (Mohs scale): 6 to 7. Color: Mottled white, pink, and gray due to feldspar, quartz, and mica. Luster: Dull (weathered) to vitreous (fresh break). Crystal Structure: Phaneritic (coarse-grained). Cleavage: Imperfect (quartz) to perfect (feldspar). Specific Gravity: 2.63 to 2.75.
- Luster
- Dull (weathered) to vitreous (fresh break)
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Physical properties
Hardness (Mohs scale): 6 to 7. Color: Mottled white, pink, and gray due to feldspar, quartz, and mica. Luster: Dull (weathered) to vitreous (fresh break). Crystal Structure: Phaneritic (coarse-grained). Cleavage: Imperfect (quartz) to perfect (feldspar). Specific Gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic) over millions of years. This specific specimen shows signs of water-rounding, suggesting it was transported by a river or glacier during the Holocene or Pleistocene epochs.
Uses & applications
Used widely in construction (crushed stone, countertops, dimension stone), landscaping, and as an educational tool for teaching mineralogy and rock cycles.
Geological facts
Granite is the primary component of the Earth's continental crust. Its name comes from the Latin 'granum', meaning a grain, in reference to its coarse-grained texture. It's one of the hardest and most durable common rocks found on the surface.
Field identification & locations
Identify in the field by its 'salt and pepper' or mottled appearance and visible crystal interlocking. It is commonly found in mountainous regions or glacial till. For collectors, look for versions with unusually large crystals (pegmatite) or unique color variations.
