igneous
Mica-bearing quartz rock, likely pegmatite
Quartz–feldspar–mica pegmatite; visible mica is probably biotite or muscovite, SiO₂ quartz
AI-generated identification · may be incorrectCoarse-grained, translucent gray-white quartz with dark, platy mica crystals and probable feldspar; vitreous quartz luster, mica pearly luster, uneven fracture, and mica basal cleavage. Quartz hardness is 7 Mohs; mica is about 2–3, with overall specific gravity roughly 2.6–2.8.
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Physical properties
Coarse-grained, translucent gray-white quartz with dark, platy mica crystals and probable feldspar; vitreous quartz luster, mica pearly luster, uneven fracture, and mica basal cleavage. Quartz hardness is 7 Mohs; mica is about 2–3, with overall specific gravity roughly 2.6–2.8.
Formation & geological history
Likely crystallized slowly from volatile-rich granitic magma in a late-stage pegmatite vein, producing unusually large crystals; commonly Precambrian to Phanerozoic depending on locality. The photograph alone cannot establish its precise age or locality.
Uses & applications
Collected as a mineral specimen; pegmatites can supply feldspar, quartz, mica, lithium, beryl, and tantalum, while gem-quality pockets may yield tourmaline or beryl. This irregular piece has little construction value.
Geological facts
Large mica books are diagnostic of pegmatitic growth, and quartz commonly forms glassy, translucent masses between them. The dark mica suggests biotite, though weathering and lighting can obscure its exact identity.
Field identification & locations
Look for centimeter-scale interlocking crystals, flexible or splitting mica sheets, glassy quartz, and feldspar cleavage faces. Common in granite terrains worldwide, including Maine, Colorado, Brazil, Madagascar, and Scandinavia.
