igneous
Quartz-rich granitic rock (likely weathered granite)
Granite; chiefly quartz (SiO₂), feldspar, and minor mica/amphibole
AI-generated identification · may be incorrectCoarse-grained, pale gray to tan, with a vitreous-to-dull luster and irregular fracture; quartz hardness is 7, while feldspar is about 6. The specimen appears weathered and locally iron-stained, with visible dark mafic minerals.
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Physical properties
Coarse-grained, pale gray to tan, with a vitreous-to-dull luster and irregular fracture; quartz hardness is 7, while feldspar is about 6. The specimen appears weathered and locally iron-stained, with visible dark mafic minerals.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, producing interlocking crystals; most examples formed during Precambrian to Phanerozoic plutonic events. Surface weathering may soften edges and discolor feldspar and iron-bearing minerals.
Uses & applications
Used widely as dimension stone, countertops, monuments, aggregate, and crushed stone; attractive polished pieces are collected but this rough fragment has little gem value.
Geological facts
Granite is an intrusive igneous rock, unlike fine-grained volcanic rhyolite, and its visible crystals indicate slow cooling. Exact identification is limited because the image does not show a fresh surface or scale.
Field identification & locations
Look for interlocking quartz, pink/white feldspar, and black mica or amphibole; it will not fizz with dilute hydrochloric acid unless carbonate veining is present. Common worldwide in continental shields and mountain belts.
