igneous
Weathered granite or granitic gneiss fragment
Granite; chiefly quartz (SiO₂), feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, pale gray to cream with dark mica-rich patches; vitreous quartz and pearly feldspar luster, interlocking crystals, no prominent cleavage as a rock. Typical constituent hardness: quartz Mohs 7, feldspar 6–6.5, mica 2–3; density about 2.6–2.7 g/cm³.
- Hardness
- quartz Mohs 7, feldspar 6–6
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Physical properties
Coarse-grained, pale gray to cream with dark mica-rich patches; vitreous quartz and pearly feldspar luster, interlocking crystals, no prominent cleavage as a rock. Typical constituent hardness: quartz Mohs 7, feldspar 6–6.5, mica 2–3; density about 2.6–2.7 g/cm³.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building events; surface weathering produced the rounded, lighter fragment.
Uses & applications
Widely used as dimension stone, countertops, monuments, crushed aggregate, and decorative landscaping material; ordinary fragments have little commercial value.
Geological facts
Granite commonly develops pink, white, gray, or black coloration depending on feldspar and accessory minerals. If foliation or distinct banding is present, the specimen may instead be granitic gneiss.
Field identification & locations
Common worldwide, especially in continental shields and mountain belts. Identify it by visible interlocking quartz, feldspar, and dark mica grains; a glassy quartz grain will not scratch easily with a steel knife, while feldspar generally may be scratched slightly.
