igneous
Granite Pebble
Granite (Felsic Plutonic Rock)
Hardness: 6-7 on Mohs scale. Color: Speckled tan, pinkish-brown, and black/dark gray. Luster: Dull to vitreous. Texture: Phaneritic (coarse-grained), rounded and stream-worn pebble. Composition: Potassium feldspar, quartz, plagioclase, and biotite/amphibole.
- Hardness
- 6-7 on Mohs scale
- Color
- Speckled tan, pinkish-brown, and black/dark gray
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Speckled tan, pinkish-brown, and black/dark gray. Luster: Dull to vitreous. Texture: Phaneritic (coarse-grained), rounded and stream-worn pebble. Composition: Potassium feldspar, quartz, plagioclase, and biotite/amphibole.
Formation & geological history
Formed beneath the Earth's surface through the slow cooling and crystallization of silica-rich magma (plutonic rock). This specific specimen has been eroded and smoothed by stream or glacial water transport over thousands to millions of years.
Uses & applications
Commonly used as construction aggregate, landscaping gravel, crushed stone, and decorative garden pebbles. Polished granite is widely used for kitchen countertops, monuments, and floor tiles.
Geological facts
Granite makes up a large portion of Earth's continental crust. The distinct speckled 'salt and pepper' look comes from the mixture of light-colored minerals (quartz and feldspar) and dark-colored ferromagnesian minerals (biotite and hornblende).
Field identification & locations
Can be identified in the field by its distinct coarse-grained, speckled interlocking crystalline texture featuring tan/pink feldspar, glassy gray quartz, and tiny black biotite flakes. Commonly found in riverbeds, glacial deposits, beaches, and mountain ranges worldwide.
