igneous
Weathered quartz-rich rock, likely granite or granitic pegmatite
Quartz–feldspar aggregate; likely granite, compositionally dominated by SiO₂-rich quartz and K-/Na-feldspar
AI-generated identification · may be incorrectHardness about 6–7 Mohs; mottled tan, cream, gray, and rusty brown with a dull to locally vitreous luster. Coarse, interlocking grains are visible, with no obvious cleavage at the specimen scale; iron staining suggests weathering.
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Physical properties
Hardness about 6–7 Mohs; mottled tan, cream, gray, and rusty brown with a dull to locally vitreous luster. Coarse, interlocking grains are visible, with no obvious cleavage at the specimen scale; iron staining suggests weathering.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the crust, probably during the Precambrian to Phanerozoic depending on locality, then exposed and weathered at the surface.
Uses & applications
Common granitic material is used for construction aggregate, dimension stone, countertops, monuments, and landscaping; this irregular fragment has mainly modest educational or decorative value.
Geological facts
The brown coloration commonly comes from oxidation of iron-bearing minerals or feldspar alteration. A glassy scratch-resistant grain is probably quartz, while blocky cream or pink grains are feldspar.
Field identification & locations
Identify it by coarse interlocking quartz and feldspar grains, lack of layering, and resistance to scratching; a steel file may scratch weathered feldspar but generally not fresh quartz. Exact identification would benefit from a fresh surface, locality, and acid test.
