igneous
Granite with Tourmaline or Biotite
Phaneritic Igneous Rock (Granoid)
Hardness: 6-7 Mohs; Color: Salt and pepper (white, grey, black); Luster: Vitreous to dull; Structure: Granular/Crystalline; Cleavage: Varies by mineral component; Specific Gravity: 2.6-2.7
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper (white, grey, black)
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (white, grey, black); Luster: Vitreous to dull; Structure: Granular/Crystalline; Cleavage: Varies by mineral component; Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. These intrusive rocks are typically found in batholiths and mountain ranges, dating back millions to billions of years.
Uses & applications
Construction (countertops, flooring), monuments, and as decorative gravel. Hand specimens are common for geological education and collecting.
Geological facts
Granite makes up a large portion of the Earth's continental crust. The black spots in this specimen are likely Schorl (black tourmaline) or Biotite mica embedded in a quartz and feldspar matrix.
Field identification & locations
Identified by its visible interlocking crystals and high quartz content. Commonly found in mountainous regions or glacial deposits. Look for the 'salt and pepper' appearance and hardness (cannot be scratched by a steel knife).
