igneous
Mica-rich pegmatite (likely muscovite-bearing)
Granitic pegmatite composed mainly of quartz, feldspar, and mica; mica is likely muscovite, KAl₂(AlSi₃O₁₀)(OH)₂
AI-generated identification · may be incorrectCoarse, uneven crystals with reflective tan-to-brown, sheet-like mica and pale quartz or feldspar. Muscovite has Mohs hardness 2–2.5 and perfect basal cleavage; quartz is 7 and feldspar about 6. The photo does not allow reliable mineral proportions or specific gravity.
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Physical properties
Coarse, uneven crystals with reflective tan-to-brown, sheet-like mica and pale quartz or feldspar. Muscovite has Mohs hardness 2–2.5 and perfect basal cleavage; quartz is 7 and feldspar about 6. The photo does not allow reliable mineral proportions or specific gravity.
Formation & geological history
Pegmatite forms when water-rich residual magma crystallizes slowly, producing exceptionally coarse crystals, commonly in veins cutting granite. Such bodies occur across many geological ages; the specimen’s age cannot be determined from the image.
Uses & applications
Pegmatite is mined for feldspar, quartz, and mica used in ceramics, glass, fillers, and electrical or thermal products; attractive mineral specimens are collected, while this piece appears modest in display value.
Geological facts
The book-like, peelable sheets are characteristic of mica, which splits into thin flexible layers. The pale, glassy-looking areas are consistent with quartz or feldspar, but visual identification alone is uncertain.
Field identification & locations
Look for coarse intergrown crystals and mica sheets that split into flakes; common settings include granitic pegmatite veins worldwide. A fresh break or simple hardness tests can help distinguish quartz from feldspar.
