igneous
Granite Pebble
Granite (Plutonic Igneous Rock)
Hardness: 6-7 on Mohs scale. Color: Grayish-tan, pink, white, and dark specks. Luster: Dull to earthy (water-worn pebble texture). Crystal Structure: Phaneritic (coarse-grained intrusive crystals of quartz, feldspar, and mica). Cleavage: None overall, though individual feldspar crystals exhibit good cleavage.
- Hardness
- 6-7 on Mohs scale
- Color
- Grayish-tan, pink, white, and dark specks
- Luster
- Dull to earthy (water-worn pebble texture)
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Grayish-tan, pink, white, and dark specks. Luster: Dull to earthy (water-worn pebble texture). Crystal Structure: Phaneritic (coarse-grained intrusive crystals of quartz, feldspar, and mica). Cleavage: None overall, though individual feldspar crystals exhibit good cleavage.
Formation & geological history
Formed deep underground by the slow cooling and crystallization of magma rich in silica and alkali metals. Over millions of years, tectonic uplift and erosion exposed the rock, and water transport (river or beach action) rounded it into a smooth pebble.
Uses & applications
River pebbles and granite stones are used in landscaping, decorative stone displays, construction aggregate, and as educational or display specimens for rock collectors.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Rounded granite pebbles indicate long-distance transport by water or glacial action.
Field identification & locations
Identify by its speckled, coarse-grained texture consisting of visible quartz, feldspar, and biotite or hornblende crystals inside a rounded, stream-worn form. Commonly found along riverbeds, beaches, and glacial till deposits worldwide.
