igneous
Weathered feldspar-rich igneous rock, likely granite or granodiorite fragment
Granite–granodiorite; chiefly quartz (SiO₂), plagioclase and potassium feldspar, with minor dark biotite/hornblende
AI-generated identification · may be incorrectCoarse, pale gray to cream, with dark inclusions and a dull-to-glassy luster; individual crystals are poorly resolved, but feldspar cleavage may be visible. Typical hardness is about 6–7 Mohs and specific gravity 2.6–2.8.
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Physical properties
Coarse, pale gray to cream, with dark inclusions and a dull-to-glassy luster; individual crystals are poorly resolved, but feldspar cleavage may be visible. Typical hardness is about 6–7 Mohs and specific gravity 2.6–2.8.
Formation & geological history
Formed by slow cooling of silica-rich magma deep in the continental crust, generally during Precambrian or younger continental plutonism; the specimen appears strongly weathered or altered.
Uses & applications
Used as crushed aggregate, building stone, monuments, and countertops; attractive polished pieces may be collected, though this fragment has little gem value.
Geological facts
Granite and granodiorite are intrusive equivalents of volcanic felsic rocks such as rhyolite and dacite. Dark patches commonly represent biotite or amphibole-rich inclusions.
Field identification & locations
Identify it by interlocking light feldspar and quartz with scattered dark minerals; a glassy fracture, acid-insensitive surface, and lack of layering support an igneous origin. Common worldwide in continental mountain belts and exposed plutons.
