igneous
Mica-rich pegmatite (likely muscovite-bearing granite)
Pegmatite; chiefly quartz (SiO₂), feldspar, and muscovite mica
AI-generated identification · may be incorrectCoarse-grained, irregular specimen with sparkling silvery-gold mica flakes and pale quartz/feldspar. Hardness is variable: mica 2–3, feldspar 6, quartz 7 Mohs; vitreous to pearly luster, with mica’s excellent basal cleavage.
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Physical properties
Coarse-grained, irregular specimen with sparkling silvery-gold mica flakes and pale quartz/feldspar. Hardness is variable: mica 2–3, feldspar 6, quartz 7 Mohs; vitreous to pearly luster, with mica’s excellent basal cleavage.
Formation & geological history
Forms when water-rich granitic magma cools slowly in dikes or pockets, allowing exceptionally large crystals to grow. Pegmatites formed mainly during Precambrian to Phanerozoic mountain-building events.
Uses & applications
Commonly collected as a mineral specimen; pegmatites may supply feldspar, quartz, mica, lithium, beryl, and rare-element ores. Attractive pieces can be used decoratively but are generally unsuitable as gemstones.
Geological facts
The bright reflective surfaces are probably mica rather than metallic gold. Mica sheets split into thin, flexible plates, a diagnostic feature.
Field identification & locations
Look for very coarse crystals, flaky elastic mica, glassy quartz, and blocky feldspar; a streak, cleavage, and hardness test can confirm components. Common worldwide, especially in granitic regions such as Brazil, India, Madagascar, and the United States.
