igneous
Pegmatitic granite fragment
Granitic pegmatite, chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse interlocking crystals with translucent gray quartz, creamy feldspar, and dark mica; vitreous to pearly luster, no obvious cleavage in quartz, Mohs hardness about 6–7, and specific gravity roughly 2.6–2.7.
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Physical properties
Coarse interlocking crystals with translucent gray quartz, creamy feldspar, and dark mica; vitreous to pearly luster, no obvious cleavage in quartz, Mohs hardness about 6–7, and specific gravity roughly 2.6–2.7.
Formation & geological history
A very coarse-grained intrusive igneous rock formed when silica-rich magma crystallized slowly in a pluton or late-stage vein. Such pegmatites are generally Precambrian to Phanerozoic, depending on locality.
Uses & applications
Used as a source of feldspar, quartz, mica, and occasionally gem minerals; attractive pieces are collected, but this small rough fragment has minimal commercial value.
Geological facts
Large crystals form because late magmatic fluids allow unusually rapid ion and element movement during crystallization. Dark flakes are probably biotite mica, while the pale blocky grains are feldspar.
Field identification & locations
Identify it by its visibly coarse texture, pale feldspar, glassy quartz, and platy dark mica; it is commonly found in granitic terrains and pegmatite veins worldwide. Exact mineral identification may require a hand lens or testing.
