igneous
Granite
Phaneritic Igneous Rock (Granite)
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (pink, gray, white, black mixture); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Dependent on mineral (feldspar has 2, quartz has none).
- Hardness
- 6-7 (Mohs scale)
- Color
- Salt and pepper (pink, gray, white, black mixture)
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (pink, gray, white, black mixture); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Dependent on mineral (feldspar has 2, quartz has none).
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. High in silica and alkali metal oxides. While the Northern Kentucky/Cincinnati region (38.9°N, 84.6°W) is covered in sedimentary rock, this specimen was likely transported there by glacial action or brought in for landscaping.
Uses & applications
Used widely in construction for countertops, floor tiles, paving stones, and memorial monuments due to its durability and aesthetic appeal.
Geological facts
The 'sunlight reflecting' mentioned by the user is due to the presence of mica (biotite or muscovite) and quartz crystals, which have flat, reflective faces. It is the most common plutonic rock in Earth's crust.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible, interlocking crystals. In sedimentary regions like the salt-rich Ohio River Valley, finding such a rock usually indicates it is a 'glacial erratic'—a rock moved hundreds of miles by ancient ice sheets.
