igneous
Quartz-rich pegmatite, possibly with feldspar and mica
Granitic pegmatite; mainly quartz (SiO₂), feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, white to gray and tan, with vitreous to pearly luster; visible interlocking crystals and dark mica inclusions. Quartz hardness is 7, feldspar 6–6.5, and mica about 2–3; cleavage is prominent in feldspar and mica but absent in quartz.
Identified More igneous →
Explore Quartz-rich pegmatite, possibly with feldspar and mica in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse-grained, white to gray and tan, with vitreous to pearly luster; visible interlocking crystals and dark mica inclusions. Quartz hardness is 7, feldspar 6–6.5, and mica about 2–3; cleavage is prominent in feldspar and mica but absent in quartz.
Formation & geological history
Likely formed as a late-stage, silica- and water-rich igneous melt cooled slowly in a granitic intrusion, producing exceptionally large crystals. Pegmatites are generally Precambrian to Cenozoic, depending on locality; the specimen’s exact age cannot be determined visually.
Uses & applications
Used as an ornamental and collectible stone; pegmatites may also host industrial quartz, feldspar, mica, lithium, beryl, and tourmaline. This small irregular piece has limited commercial value.
Geological facts
The translucent, glassy areas are probably quartz, while blocky cream crystals are feldspar and glittering dark or silvery flakes are mica. Pegmatites are among the principal sources of large gemstone crystals.
Field identification & locations
Common in exposed granitic terrains worldwide, including Brazil, the United States, Madagascar, and Norway. Test with a steel knife or glass: quartz should resist scratching steel and scratch glass, whereas feldspar generally does not.
