igneous
Weathered granite or granitic gneiss
Coarse-grained quartz–feldspar–mica rock; likely granite, possibly gneiss
AI-generated identification · may be incorrectTypically 6–7 Mohs; pale gray, cream, and brown with visible quartz and feldspar grains, dark biotite, granular texture, vitreous quartz luster, and no obvious cleavage as a whole rock. The rounded edges indicate prolonged weathering or abrasion.
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Physical properties
Typically 6–7 Mohs; pale gray, cream, and brown with visible quartz and feldspar grains, dark biotite, granular texture, vitreous quartz luster, and no obvious cleavage as a whole rock. The rounded edges indicate prolonged weathering or abrasion.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building events; gneiss is metamorphosed granite. Weathering and transport rounded this specimen.
Uses & applications
Used as crushed aggregate, building stone, paving, monuments, and landscaping rock; attractive polished pieces may be decorative but this specimen appears ordinary.
Geological facts
The interlocking crystals indicate slow underground cooling rather than volcanic eruption. Brown staining likely represents iron-oxide weathering along fractures.
Field identification & locations
Identify it by coarse interlocking quartz and feldspar with scattered dark mica; a streak test is generally unhelpful, while quartz scratches glass. Common worldwide, especially in continental shield and mountain regions.
