igneous
Granite Pebble
Granite (composed primarily of Quartz SiO2, Feldspar KAlSi3O8, and Mica)
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white, grey, black); Luster: Vitreous to dull; Crystal structure: Phaneritic (medium to coarse-grained crystals); Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 Mohs
- Color
- Salt-and-pepper (white, grey, black)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white, grey, black); Luster: Vitreous to dull; Crystal structure: Phaneritic (medium to coarse-grained crystals); Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed through the slow crystallization of magma below the Earth's surface (intrusive). This specimen shows rounding and smoothing, indicating it was later eroded and transported by water, likely in a river or beach setting.
Uses & applications
Used widely in construction (countertops, flooring), monuments, and as crushed stone for road base. Rounded pebbles like this are often used in landscaping and decorative masonry.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Because it is extremely resistant to weathering, it often forms the core of major mountain ranges.
Field identification & locations
Identify by looking for a speckled appearance of interlocking crystals with no preferred orientation. White/pink parts are feldspar, clear/grey is quartz, and black flakes are mica or amphibole. Commonly found in mountainous regions or glacial deposits.
