igneous
Quartz-rich feldspar rock, possibly pegmatitic granite
Granite or granitic pegmatite; mainly quartz (SiO₂) and feldspar, with possible mica
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pale tan to gray, translucent in spots, with a vitreous to uneven luster and coarse interlocking grains. No obvious cleavage is visible, though feldspar may show cleavage surfaces.
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Physical properties
Hardness about 6–7 Mohs; pale tan to gray, translucent in spots, with a vitreous to uneven luster and coarse interlocking grains. No obvious cleavage is visible, though feldspar may show cleavage surfaces.
Formation & geological history
Likely crystallized slowly from silica-rich magma, producing large quartz and feldspar grains; commonly Precambrian to Phanerozoic in age depending on locality. Exact identification requires a fresh surface, streak, and hardness testing.
Uses & applications
Used as building and dimension stone when massive; small specimens are mainly collected for their quartz-feldspar texture. It has little gem value unless transparent quartz or attractive feldspar crystals are present.
Geological facts
The granular, mixed appearance is more consistent with a quartz-feldspar aggregate than a single mineral. Yellow-brown coloration may result from iron staining or weathering.
Field identification & locations
Common in continental crust, pegmatite veins, and granitic terrains worldwide. Test glass scratching, inspect grain boundaries with magnification, and use dilute acid only if carbonate minerals are suspected.
