igneous
Granite (River-worn pebble)
Phaneritic plutonic rock (SiO2 + Al2O3)
Hardness: 6-7 on Mohs scale; Color: Mottled gray, white, and black; Luster: Dull to vitreous; Crystal structure: Phaneritic (medium-grained visible crystals of quartz, feldspar, and mica); Cleavage: None (fractures unevenly).
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled gray, white, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled gray, white, and black; Luster: Dull to vitreous; Crystal structure: Phaneritic (medium-grained visible crystals of quartz, feldspar, and mica); Cleavage: None (fractures unevenly).
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen has been chemically and physically weathered by water transport, likely in a river or glacial deposit, resulting in its rounded shape.
Uses & applications
Large deposits are used in construction for countertops, monuments, and road aggregate. This small pebble has mainly educational or decorative landscape value.
Geological facts
Granite makes up the majority of the Earth's continental crust. It is one of the hardest natural stones, which is why it is often chosen for durable public monuments.
Field identification & locations
Identify in the field by looking for a 'salt and pepper' appearance with visible interlocking crystals of different colors. It will not be scratched by a steel pocketknife. Commonly found in mountainous regions or riverbeds.
