igneous
Granite Pebble on Flagstone
Granite (Felsic Plutonic Rock)
Hardness: 6-7 Mohs; Color: Salt and pepper (gray, white, black); Luster: Dull to vitreous; Structure: Phaneritic (medium-grained crystalline); Specific Gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper (gray, white, black)
- Luster
- Dull to vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (gray, white, black); Luster: Dull to vitreous; Structure: Phaneritic (medium-grained crystalline); Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen is a water-worn or weathered pebble found resting on a metamorphic slate or flagstone surface.
Uses & applications
Used extensively in construction, countertops, monuments, and as aggregate. Pebbles like this are common in landscaping and riverbeds.
Geological facts
Granite is the most common igneous rock found on Earth's continents. It contains mainly quartz, feldspar, and mica. The pinkish tones sometimes seen are due to potassium feldspar.
Field identification & locations
Identify by its visible interlocking crystals of quartz (clearish gray), feldspar (white/pink), and mica/hornblende (black). Commonly found in glaciated regions or riverbeds as rounded 'cobbles'.
