igneous
Pegmatitic mica-quartz-feldspar specimen
Granitic pegmatite, chiefly quartz (SiO₂), feldspar, and muscovite/biotite mica
AI-generated identification · may be incorrectCoarse, interlocking crystals with pearly-to-glassy luster; white translucent quartz/feldspar contrasts with bronze-gray, platy mica. Quartz hardness ~7, feldspar ~6, mica ~2–3; cleavage is prominent in mica and feldspar, with no cleavage in quartz.
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Physical properties
Coarse, interlocking crystals with pearly-to-glassy luster; white translucent quartz/feldspar contrasts with bronze-gray, platy mica. Quartz hardness ~7, feldspar ~6, mica ~2–3; cleavage is prominent in mica and feldspar, with no cleavage in quartz.
Formation & geological history
Formed when water-rich, silica-rich magma cooled slowly in late-stage veins, allowing exceptionally large crystals to grow. Pegmatites are mostly Precambrian to Mesozoic, depending on locality.
Uses & applications
Used as a collector specimen; pegmatites are important sources of feldspar, mica, quartz, lithium, beryl, and rare-element minerals. This irregular piece has little construction or jewelry value.
Geological facts
The reflective surfaces are likely mica cleavage faces, while the translucent massive areas are quartz or feldspar. Exact identification would require hardness, streak, and possibly chemical or microscopic testing.
Field identification & locations
Common in granitic regions worldwide, including Brazil, the United States, Madagascar, and India. Look for very coarse crystals, mica books, and sharp mineral boundaries; avoid assuming every silvery area is metallic ore.
