igneous
Quartz-rich pegmatite (likely milky quartz with feldspar and mica)
Granite pegmatite; chiefly quartz (SiO₂), with feldspar and mica-group minerals
AI-generated identification · may be incorrectWhite to gray, translucent patches with vitreous to pearly luster and coarse interlocking crystals; quartz hardness 7, feldspar ~6, mica ~2–3, with irregular fracture and locally perfect mica cleavage. Specific gravity is approximately 2.6–2.7.
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Physical properties
White to gray, translucent patches with vitreous to pearly luster and coarse interlocking crystals; quartz hardness 7, feldspar ~6, mica ~2–3, with irregular fracture and locally perfect mica cleavage. Specific gravity is approximately 2.6–2.7.
Formation & geological history
Forms when the final, water-rich melt from a granitic magma crystallizes slowly in veins or pockets, producing unusually coarse crystals; typically associated with Precambrian to younger continental crust.
Uses & applications
Used as a decorative and collecting specimen; quartz and feldspar from pegmatites can be used in glass, ceramics, and construction aggregate, while exceptional crystals may be gem or mineral specimens.
Geological facts
The bluish translucent areas are probably milky quartz, while sparkling platy surfaces may be mica; exact identification would require close inspection or testing.
Field identification & locations
Look for very coarse crystals, glassy quartz, blocky feldspar, and flaky mica. Common in granitic terrains worldwide, especially Brazil, Madagascar, the United States, and Scandinavia.
