igneous
Granite
Phaneritic Granitoid
Hardness: 6-7 on Mohs scale; Color: Mottled pink, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Cleavage: Perfect on feldspar grains; Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, white, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled pink, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Cleavage: Perfect on feldspar grains; Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). This specific rounded specimen suggests it was tumbled in water (river or beach) over many years. Granite is primarily associated with the continental crust and can range from millions to billions of years old.
Uses & applications
Widely used in construction, countertops, monuments, and as a decorative stone in landscaping. Its durability also makes it a popular choice for curling stones and memorials.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. It is one of the hardest and most common rocks found on the planet.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking mineral crystals. It is found in mountain ranges and areas where deep-seated igneous rocks have been exposed by erosion. For collectors, it is often gathered from riverbeds where water has naturally polished the stones.
