igneous
Granite (Worn Pebble)
Granite
Hardness: 6-7 Mohs; Color: Mottled white, pink, grey, and black; Luster: Vitreous to dull (depending on water content); Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Mottled white, pink, grey, and black
- Luster
- Vitreous to dull (depending on water content)
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled white, pink, grey, and black; Luster: Vitreous to dull (depending on water content); Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.63-2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This specific specimen appears to be a river-worn or beach-tumbled pebble, likely millions of years old, shaped by water erosion.
Uses & applications
Used extensively in construction (countertops, flooring), monuments, and as crushed stone for road base. Smooth pebbles are often used in landscaping and aquariums.
Geological facts
Granite makes up a large portion of the continental crust. It is one of the hardest and most durable natural stones, which is why it has been used in architecture since ancient Egypt.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. It will not scratch with a copper penny or a steel knife. Common in mountainous regions and glacial deposits.
