igneous
Quartz-rich pegmatite (likely feldspar–quartz rock)
Granitic pegmatite; predominantly quartz (SiO₂) and feldspar, with possible mica and iron-oxide staining
AI-generated identification · may be incorrectCoarse-grained, pale gray to white, vitreous to pearly luster, irregular fracture, and interlocking crystals; quartz hardness 7 and feldspar about 6–6.5 Mohs. The image does not resolve crystal boundaries well enough for a precise mineral identification.
Identified More igneous →
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Physical properties
Coarse-grained, pale gray to white, vitreous to pearly luster, irregular fracture, and interlocking crystals; quartz hardness 7 and feldspar about 6–6.5 Mohs. The image does not resolve crystal boundaries well enough for a precise mineral identification.
Formation & geological history
Formed when silica- and water-rich magma cooled slowly in a late-stage igneous vein, producing unusually large crystals; commonly Precambrian to younger, depending on locality.
Uses & applications
Used decoratively and as a source of quartz, feldspar, mica, and specialty minerals; attractive pieces may be collected, but this specimen is not gem-quality.
Geological facts
Pegmatites can host tourmaline, beryl, garnet, lithium minerals, and rare elements. Dark patches may be biotite, amphibole, or weathered iron/manganese minerals.
Field identification & locations
Common in granitic terrains and metamorphic belts worldwide, including the United States, Brazil, Madagascar, and Scandinavia. Look for very coarse interlocking quartz and feldspar, glassy quartz, and mica; a white streak and hardness near 7 support quartz.
