igneous
Plutonic Granite (Water-worn Pebble)
Granite
Hardness: 6-7 (Mohs); Color: Mottled gray, black, and white; Luster: Dull (weathered/tumbled); Crystal structure: Phaneritic (visible crystals); Composition: Quartz, Feldspar, and Biotite/Mica
- Hardness
- 6-7 (Mohs)
- Color
- Mottled gray, black, and white
- Luster
- Dull (weathered/tumbled)
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Physical properties
Hardness: 6-7 (Mohs); Color: Mottled gray, black, and white; Luster: Dull (weathered/tumbled); Crystal structure: Phaneritic (visible crystals); Composition: Quartz, Feldspar, and Biotite/Mica
Formation & geological history
Formed through the slow cooling of silica-rich magma deep beneath the Earth's surface (plutonic). This specific specimen has been rounded by mechanical erosion in a high-energy environment like a river or beach.
Uses & applications
Crushed stone for construction, architectural veneer, or as common garden decorative pebbles.
Geological facts
Granite makes up much of the Earth's continental crust. The dark spots are typically biotite mica or hornblende, while the lighter parts are quartz and feldspar.
Field identification & locations
Identify by its 'salt and pepper' grainy appearance and hardness; it cannot be scratched by a steel knife. Commonly found in glaciated regions or areas with exposed batholiths.
