igneous
Pegmatitic quartz–feldspar rock
Granite or granitic pegmatite; chiefly quartz (SiO₂), feldspar, and minor mica/amphibole
AI-generated identification · may be incorrectCoarse-grained, pale translucent gray to cream, with a glassy to pearly luster and interlocking crystals; quartz hardness 7, feldspar about 6, with no obvious cleavage in quartz but cleavage in feldspar. Specific gravity is typically about 2.6–2.7.
Identified More igneous →
Explore Pegmatitic quartz–feldspar rock in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse-grained, pale translucent gray to cream, with a glassy to pearly luster and interlocking crystals; quartz hardness 7, feldspar about 6, with no obvious cleavage in quartz but cleavage in feldspar. Specific gravity is typically about 2.6–2.7.
Formation & geological history
Likely formed from slowly cooled, silica-rich magma, allowing large crystals to grow; commonly associated with Precambrian to younger granitic intrusions. The exact rock name requires a fresh surface or thin-section examination.
Uses & applications
Used as decorative stone, aggregate, and a source of quartz and feldspar; attractive pieces may be collected, though this specimen appears ordinary rather than gem grade.
Geological facts
The glassy grains are likely quartz, while blockier cloudy grains are feldspar; dark flakes or patches may be biotite or amphibole. Pegmatites can also host tourmaline, beryl, lithium minerals, and other collectible crystals.
Field identification & locations
Common in granitic terrains worldwide, including the United States, Canada, Brazil, India, and Scandinavia. Identify it by its very coarse interlocking texture, hardness, and quartz-rich appearance; a vinegar test is not diagnostic.
