igneous
Granite (Dioritic variant)
Granite (Phaneritic Igneous Rock)
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (yellowish-white feldspar and black biotite/amphibole). Luster: Dull to vitreous when wet. Crystal structure: Phaneritic (coarse-grained visible crystals). Specific Gravity: 2.6-2.7.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to vitreous when wet
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (yellowish-white feldspar and black biotite/amphibole). Luster: Dull to vitreous when wet. Crystal structure: Phaneritic (coarse-grained visible crystals). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed by the slow cooling of silica-rich magma deep within the Earth's crust (plutonic). This specimen appears to be water-worn, smoothed by fluvial or coastal transport over thousands of years.
Uses & applications
Commonly used in heavy construction, countertops, monuments, and as crushed stone for road bases. Polished versions are used in high-end interior design.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Because it is so hard and durable, it is often the primary material for mountain ranges like the Sierra Nevada.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals. It is found globally in continental shields and mountain belts. This specific smooth pebble is likely found in a riverbed or beach near a mountain source.
