igneous
Quartz-rich pegmatite (likely quartz with feldspar)
Pegmatitic granite; chiefly quartz (SiO₂) and feldspar, with possible mica and iron-oxide staining
AI-generated identification · may be incorrectCoarse, irregular white-to-gray mass with glassy to dull luster and rusty brown staining; quartz hardness 7, feldspar 6–6.5, generally poor cleavage in the overall specimen. The image does not resolve individual crystals well enough for a certain mineral identification.
Identified More igneous →
Explore Quartz-rich pegmatite (likely quartz with feldspar) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse, irregular white-to-gray mass with glassy to dull luster and rusty brown staining; quartz hardness 7, feldspar 6–6.5, generally poor cleavage in the overall specimen. The image does not resolve individual crystals well enough for a certain mineral identification.
Formation & geological history
Likely formed from the final, water-rich melt of a slowly cooling granitic intrusion, producing exceptionally coarse crystals during the Precambrian to Phanerozoic. Weathering has exposed and stained the surface with iron oxides.
Uses & applications
Used decoratively and as a source of quartz and feldspar for glass, ceramics, and industrial materials; attractive crystals may be collected, though this rough piece appears primarily a common specimen.
Geological facts
Pegmatites can host large crystals and rare minerals such as tourmaline, beryl, and lithium minerals. Brown coloration commonly results from limonite or other iron-oxide coatings rather than the primary rock.
Field identification & locations
Look for interlocking coarse quartz and feldspar grains, a white translucent quartz component, and hardness sufficient to scratch glass; acid testing is unnecessary. Common in granitic terrains and pegmatite districts worldwide.
