igneous
Pegmatite (Feldspar and Quartz)
Pegmatite (KAlSi3O8 / SiO2)
Hardness 6-7 on Mohs scale; color ranges from tan, cream, beige to translucent grey; vitreous to pearly luster; coarse-grained to blocky crystal structure with distinct feldspar cleavage planes.
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Physical properties
Hardness 6-7 on Mohs scale; color ranges from tan, cream, beige to translucent grey; vitreous to pearly luster; coarse-grained to blocky crystal structure with distinct feldspar cleavage planes.
Formation & geological history
Formed during the final stages of a magma body's crystallization, where water-rich fluids allow extremely large mineral crystals to grow rapidly in granitic intrusions.
Uses & applications
Feldspar extracted from pegmatites is widely used in ceramics, glass manufacturing, and mild abrasives, as well as a source for rare minerals.
Geological facts
Pegmatites are famous among mineral collectors because they contain the largest mineral crystals ever found on Earth, sometimes measuring several meters across.
Field identification & locations
Identified by its very coarse grain size and intergrown tan feldspar and glassy quartz. Commonly found in granitic mountainous terrains worldwide.
