igneous
Quartz-bearing rock, possibly weathered granite or pegmatite
Quartz–feldspar–mica aggregate; exact classification is uncertain from the image
AI-generated identification · may be incorrectCoarse, irregular interlocking grains include translucent gray quartz, pale feldspar, and dark mica or altered mafic minerals; quartz is Mohs 7, with vitreous luster and no cleavage, while feldspar shows two cleavages. The rusty brown areas are likely iron-oxide weathering.
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Physical properties
Coarse, irregular interlocking grains include translucent gray quartz, pale feldspar, and dark mica or altered mafic minerals; quartz is Mohs 7, with vitreous luster and no cleavage, while feldspar shows two cleavages. The rusty brown areas are likely iron-oxide weathering.
Formation & geological history
Likely crystallized slowly from silica-rich magma as granite or pegmatite, then fractured and chemically weathered near the surface; its geological age cannot be determined visually and may range from Precambrian to Cenozoic.
Uses & applications
Unusual pieces may be used as teaching or display specimens; ordinary material has little industrial value compared with sound granite used for aggregate, building stone, and countertops.
Geological facts
The large translucent grains and coarse texture indicate slow cooling underground rather than volcanic eruption. Brown staining commonly develops when iron-bearing minerals oxidize during weathering.
Field identification & locations
Look for glassy gray quartz, blocky white feldspar, and black mica in a coarse texture; a knife should not scratch quartz, while feldspar can be scratched by hardened steel. Common worldwide in granitic and pegmatitic terrains.
