igneous
Granite Pegmatite
Phaneritic Felsic Igneous Rock (Granite)
Hardness: 6-7 on Mohs scale; Color: Salt and pepper appearance with visible gray quartz, white feldspar, and shiny silver/black mica; Luster: Vitreous to pearly; Crystal structure: Phaneritic/Pegmatitic (large crystals); Cleavage: Perfect mica cleavage visible.
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper appearance with visible gray quartz, white feldspar, and shiny silver/black mica; Luster: Vitreous to pearly; Crystal structure: Phaneritic/Pegmatitic (large crystals); Cleavage: Perfect mica cleavage visible.
Formation & geological history
Formed from the slow cooling and crystallization of molten magma deep within the Earth's crust (plutonic). This specimen shows exceptionally large mineral grains characteristic of the final stages of magma crystallization.
Uses & applications
Used extensively in construction (countertops, flooring, monuments), as crushed stone for road base, and as a source for industrial minerals like quartz and mica.
Geological facts
Granite makes up a large portion of the continental crust. The presence of large mica flakes (muscovite or biotite) as seen in the image indicates a high concentration of water in the magma during cooling.
Field identification & locations
Identify by looking for interlocked crystals of quartz, feldspar, and mica. It is found in large mountain ranges and ancient continental shields. For collectors, the presence of large, well-defined mica sheets or quartz pockets increases value.
