igneous
Quartz-bearing feldspathic rock, likely weathered granite or pegmatite
Granite/pegmatite; chiefly quartz (SiO₂) and feldspar, with possible mica
AI-generated identification · may be incorrectCoarse-grained, pale gray to tan, with translucent glassy quartz and blocky feldspar crystals; hardness about 6–7, vitreous to pearly luster, irregular fracture, and low-to-moderate specific gravity (~2.6).
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Physical properties
Coarse-grained, pale gray to tan, with translucent glassy quartz and blocky feldspar crystals; hardness about 6–7, vitreous to pearly luster, irregular fracture, and low-to-moderate specific gravity (~2.6).
Formation & geological history
Formed when silica-rich magma cooled slowly underground, allowing large crystals to grow; likely Precambrian to younger depending on locality. Surface weathering has produced the rough, crumbly exterior.
Uses & applications
Used as construction stone, aggregate, countertops, and decorative material; attractive quartz-rich pieces may be collected but are generally not gemstone grade.
Geological facts
The image suggests a rock rather than a single mineral because multiple interlocking crystal types are visible. A close view or hardness/streak tests would be needed to distinguish granite from pegmatite.
Field identification & locations
Common in continental crust and exposed in regions such as the Sierra Nevada, Appalachians, Canadian Shield, and many mountain belts. Identify it by visible quartz, feldspar, and possible mica in a coarse interlocking texture.
