igneous
Quartz-bearing granite or gneiss fragment
Granite/gneiss composed mainly of quartz (SiO₂), feldspar, and minor mica or ferromagnesian minerals
AI-generated identification · may be incorrectGray-white, coarse-grained, irregular specimen with translucent quartz and pale feldspar; vitreous quartz luster, Mohs hardness about 6–7, no prominent cleavage in quartz, and moderate-to-high specific gravity around 2.6–2.8. The image is insufficient to distinguish granite from weathered gneiss confidently.
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Physical properties
Gray-white, coarse-grained, irregular specimen with translucent quartz and pale feldspar; vitreous quartz luster, Mohs hardness about 6–7, no prominent cleavage in quartz, and moderate-to-high specific gravity around 2.6–2.8. The image is insufficient to distinguish granite from weathered gneiss confidently.
Formation & geological history
Likely formed by slow crystallization of silica-rich magma deep in the crust (granite) or recrystallization and deformation of similar rock (gneiss), generally during Precambrian to Phanerozoic mountain-building events.
Uses & applications
Commonly used as crushed stone, aggregate, building stone, and decorative material; attractive pieces may be kept as field specimens, though this fragment has little gem value.
Geological facts
Quartz appears as glassy or translucent gray patches, while feldspar is generally opaque white or pink; dark flecks may be biotite or amphibole.
Field identification & locations
Common worldwide, especially in continental shields and mountain belts. Look for interlocking visible grains and distinguish it from concrete by its natural irregular texture and lack of uniform cement or manufactured aggregate.
