igneous
Pegmatitic Granite
Granite (Alkali-feldspar granite) with Quartz and Orthoclase
Hardness: 6-7 (Mohs scale); Color: Pink (feldspar) and White/Clear (quartz); Luster: Vitreous to pearly; Crystal structure: Phaneritic/Pegmatitic (large crystals); Cleavage: Perfect in feldspar, none in quartz.
- Hardness
- 6-7 (Mohs scale)
- Color
- Pink (feldspar) and White/Clear (quartz)
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Pink (feldspar) and White/Clear (quartz); Luster: Vitreous to pearly; Crystal structure: Phaneritic/Pegmatitic (large crystals); Cleavage: Perfect in feldspar, none in quartz.
Formation & geological history
Formed from the slow cooling of magma deep underground, often in the late stages of a pluton's crystallization where mineral-rich fluids facilitate large crystal growth.
Uses & applications
Commonly used as crushed stone in construction, dimension stone for countertops and tiles, and as a source for extracting specific minerals like feldspar or mica.
Geological facts
This specimen contains Orthoclase feldspar, which gets its pink color from trace amounts of iron or potassium within the crystal lattice. Large-grained granite is often called pegmatite if the grains are larger than 2.5 cm.
Field identification & locations
Identify by looking for intergrown crystals of pink feldspar and glassy quartz. Found worldwide in continental crust, particularly in mountain belts and ancient shield areas like the Appalachians or the Canadian Shield.
