igneous
Weathered granite or granitic gneiss
Granite; quartz + feldspar + biotite/hornblende, possibly weakly gneissic
AI-generated identification · may be incorrectCoarse, speckled gray rock with pink-orange weathered feldspar and dark mafic minerals; quartz gives a glassy sheen. Mohs hardness about 6–7, granular crystal structure, no obvious cleavage as a whole, and specific gravity roughly 2.6–2.8.
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Physical properties
Coarse, speckled gray rock with pink-orange weathered feldspar and dark mafic minerals; quartz gives a glassy sheen. Mohs hardness about 6–7, granular crystal structure, no obvious cleavage as a whole, and specific gravity roughly 2.6–2.8.
Formation & geological history
Formed when silica-rich magma cooled slowly deep underground, likely during Precambrian to younger continental crust formation; surface weathering has oxidized iron-bearing minerals and feldspar.
Uses & applications
Widely used as dimension stone, countertops, paving, monuments, crushed aggregate, and building material; this weathered hand specimen has little commercial value.
Geological facts
The pink coloration commonly comes from potassium feldspar altered by oxidation and weathering. The dark grains are likely biotite mica or hornblende, while the pale translucent grains are quartz and feldspar.
Field identification & locations
Identify it by visible interlocking grains, hardness, and lack of layering; it should scratch glass and resist weak acid. Common in continental mountain belts and glacial deposits worldwide; distinguishing granite from gneiss requires checking for mineral banding, which is not clear here.
