igneous
Smoky quartz-bearing pegmatite (probable)
Quartz, SiO₂, with abundant feldspar and mica inclusions
AI-generated identification · may be incorrectHardness about 7 for quartz; translucent gray-brown to smoky, with vitreous luster and irregular fracture. The coarse, interlocking texture suggests pegmatite, though the specimen may include mica or feldspar that affects its apparent hardness and cleavage.
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Physical properties
Hardness about 7 for quartz; translucent gray-brown to smoky, with vitreous luster and irregular fracture. The coarse, interlocking texture suggests pegmatite, though the specimen may include mica or feldspar that affects its apparent hardness and cleavage.
Formation & geological history
Likely formed from the final, water-rich fluids of a slowly cooling granitic magma, producing unusually large crystals. Pegmatites are mostly Precambrian to Phanerozoic and occur in continental mountain belts and granitic terrains.
Uses & applications
Used mainly as a mineral collector’s specimen; quartz can be used in glass, electronics, and abrasives, while pegmatites may host lithium, feldspar, mica, and gem minerals.
Geological facts
The dark coloration may be smoky quartz caused by natural irradiation and trace aluminum, or simply dark mica inclusions. A definitive identification requires a fresh surface, hardness testing, and inspection for feldspar cleavage.
Field identification & locations
Common in granite-pegmatite districts worldwide, including Brazil, Madagascar, the United States, and the Alps. Look for glassy quartz, blocky feldspar, and flaky mica; avoid acid testing, and use a steel file or quartz-point scratch test cautiously.
