igneous
Quartz-rich pegmatite
Granitic pegmatite, composed mainly of quartz (SiO₂) and feldspar, with dark mica or other accessory minerals
AI-generated identification · may be incorrectCoarse, interlocking white to gray crystals with dark inclusions; quartz has Mohs hardness 7 and glassy luster, while feldspar is about 6. The photo does not show enough detail to identify the dark mineral confidently.
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Physical properties
Coarse, interlocking white to gray crystals with dark inclusions; quartz has Mohs hardness 7 and glassy luster, while feldspar is about 6. The photo does not show enough detail to identify the dark mineral confidently.
Formation & geological history
Likely crystallized from silica-rich magma in a slowly cooling intrusion or late-stage vein. Pegmatites are commonly Precambrian but occur in rocks of many ages.
Uses & applications
Pegmatite is mined for quartz, feldspar, mica, and specialty elements; attractive pieces are kept as specimens, though this one appears unworked.
Geological facts
Pegmatites can host exceptionally large crystals and valuable minerals such as tourmaline, beryl, and spodumene.
Field identification & locations
Look for unusually coarse interlocking crystals and quartz’s lack of cleavage; common in granitic terrains and exposed veins. Confirming the identification requires closer inspection or testing.
