igneous
Pegmatitic granite with smoky quartz and feldspar
Granitic pegmatite; chiefly quartz (SiO₂), feldspar, and mica, with possible tourmaline or hornblende
AI-generated identification · may be incorrectCoarse-grained, interlocking crystals with translucent gray-brown quartz, cream/pink feldspar, and dark mica or amphibole; vitreous quartz luster, feldspar cleavage, Mohs hardness about 6–7, and specific gravity roughly 2.6–2.7.
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Physical properties
Coarse-grained, interlocking crystals with translucent gray-brown quartz, cream/pink feldspar, and dark mica or amphibole; vitreous quartz luster, feldspar cleavage, Mohs hardness about 6–7, and specific gravity roughly 2.6–2.7.
Formation & geological history
Formed from slowly cooling, water-rich residual magma in veins or pockets within continental crust, commonly during Precambrian to Phanerozoic intrusive events.
Uses & applications
Used as a decorative and architectural stone; pegmatites are important sources of feldspar, quartz, mica, lithium minerals, and collectible crystals, though this specimen is mainly a display piece.
Geological facts
The exceptionally large crystals result from volatile-rich melt and very slow cooling; dark zones may be biotite mica, schorl tourmaline, or amphibole, which cannot be confirmed from the image alone.
Field identification & locations
Identify it by its unusually coarse texture, glassy quartz, blocky feldspar, and platy dark mica; common in granite terrains and pegmatite districts worldwide, including Brazil, Madagascar, the United States, and Scandinavia.
