igneous
Quartz-rich pegmatite with mica
Granitic pegmatite; chiefly quartz (SiO₂), feldspar, and muscovite/biotite mica
AI-generated identification · may be incorrectCoarse, interlocking crystals; milky to translucent quartz has vitreous luster, feldspar is white and blocky, and mica forms shiny platy flakes. Quartz hardness is 7, feldspar 6–6.5, and mica 2–3; cleavage is prominent in mica and feldspar but absent in quartz.
Identified More igneous →
Explore Quartz-rich pegmatite with mica in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse, interlocking crystals; milky to translucent quartz has vitreous luster, feldspar is white and blocky, and mica forms shiny platy flakes. Quartz hardness is 7, feldspar 6–6.5, and mica 2–3; cleavage is prominent in mica and feldspar but absent in quartz.
Formation & geological history
Forms when late-stage, water-rich granitic magma cools slowly in dikes or veins, producing exceptionally large crystals. Pegmatites range from Precambrian to recent geologic ages and commonly host hydrothermal mineralization.
Uses & applications
Used as a source of feldspar, quartz, mica, and occasionally lithium, tantalum, beryllium, or gemstones; attractive pieces are sold as cabinet specimens, though this example appears common.
Geological facts
The apparent metallic gray surfaces are likely mica or weathered sulfide-bearing zones rather than true metal. Pegmatites can contain spectacular tourmaline, beryl, garnet, and rare-element minerals.
Field identification & locations
Identify it by very coarse grain size, glassy quartz, blocky feldspar, and peelable mica sheets; common in granitic terrains worldwide, including Brazil, the United States, Madagascar, and India. A definitive identification may require hardness, streak, or analytical testing.
