igneous
Quartz-rich pegmatite (likely mica-bearing granite)
Granitic pegmatite; chiefly quartz (SiO₂), feldspar, and mica (muscovite/biotite)
AI-generated identification · may be incorrectCoarse, interlocking crystals with white to gray quartz/feldspar and reflective mica flakes; generally vitreous to pearly luster. Quartz hardness is 7 Mohs; feldspar is about 6, and mica about 2–3, with mica showing perfect basal cleavage.
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Physical properties
Coarse, interlocking crystals with white to gray quartz/feldspar and reflective mica flakes; generally vitreous to pearly luster. Quartz hardness is 7 Mohs; feldspar is about 6, and mica about 2–3, with mica showing perfect basal cleavage.
Formation & geological history
Forms when water-rich granitic magma cools slowly in dikes or pockets, allowing exceptionally large crystals to grow. Most pegmatites are Precambrian to Mesozoic, though ages vary by locality.
Uses & applications
Commonly collected as a mineral specimen; larger, sound material may provide feldspar, quartz, mica, or gem minerals. It has limited construction use compared with ordinary granite.
Geological facts
The sparkly, platy surfaces are likely mica rather than metallic ore. Pegmatites can host tourmaline, beryl, garnet, lithium minerals, and rare-earth minerals.
Field identification & locations
Identify it by coarse visible crystals, glassy quartz, blocky feldspar, and peelable mica sheets; a knife will not scratch quartz. Common in granitic terrains and pegmatite districts worldwide.
