igneous
Golden mica-bearing feldspar pegmatite
Muscovite (KAl₂(AlSi₃O₁₀)(OH)₂) with potassium feldspar, likely pegmatitic granite
AI-generated identification · may be incorrectHardness is approximately 2–2.5 for muscovite and 6 for feldspar; the specimen is yellow-gold, pearly to vitreous, with prominent elastic sheet cleavage in mica and blocky cleavage in feldspar. Its coarse crystals indicate a pegmatitic texture; specific gravity is roughly 2.6–2.8.
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Physical properties
Hardness is approximately 2–2.5 for muscovite and 6 for feldspar; the specimen is yellow-gold, pearly to vitreous, with prominent elastic sheet cleavage in mica and blocky cleavage in feldspar. Its coarse crystals indicate a pegmatitic texture; specific gravity is roughly 2.6–2.8.
Formation & geological history
Formed from slowly cooling, volatile-rich granitic magma in a pegmatite vein, allowing exceptionally large crystals to grow. Such pegmatites are generally Precambrian to Phanerozoic in age, depending on locality.
Uses & applications
Collected as a mineral specimen; muscovite is used industrially for electrical insulation, fillers, and heat-resistant products, while feldspar is used in ceramics and glass. Attractive pieces may be sold as cabinet specimens.
Geological facts
The golden color commonly results from iron staining or iron-bearing muscovite varieties such as phlogopite. Mica’s sheets can be split into extremely thin, flexible layers.
Field identification & locations
Identify it by its glittering, peelable sheets and associated cream-to-pink feldspar; common sources include Brazil, Madagascar, India, Russia, and U.S. pegmatite districts. Avoid soaking or abrasive cleaning, which can damage the mica.
