igneous
Granite (likely weathered glacial erratic)
Granite; predominantly quartz, alkali feldspar, plagioclase, and minor mica
AI-generated identification · may be incorrectCoarse-grained, light gray rock with a granular texture and scattered darker minerals; quartz and feldspar have Mohs hardness 6–7, with nonmetallic to slightly vitreous luster. It typically lacks cleavage as a whole, though feldspar grains show cleavage; specific gravity is about 2.63–2.75.
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Physical properties
Coarse-grained, light gray rock with a granular texture and scattered darker minerals; quartz and feldspar have Mohs hardness 6–7, with nonmetallic to slightly vitreous luster. It typically lacks cleavage as a whole, though feldspar grains show cleavage; specific gravity is about 2.63–2.75.
Formation & geological history
Intrusive igneous rock crystallized slowly from silica-rich magma deep in the crust, commonly during Precambrian to Mesozoic episodes. Its rounded surface and outdoor setting may indicate transport and abrasion by Pleistocene glaciers.
Uses & applications
Widely used as building stone, paving, monuments, countertops, aggregate, and landscaping rock. Unusual, polished pieces may be used decoratively, but this weathered specimen has little gem value.
Geological facts
Granite’s visible grains reflect slow underground cooling; pink, white, and gray varieties are controlled mainly by feldspar and quartz proportions. Weathering commonly produces a rough, crumbly surface and lichen cover.
Field identification & locations
Identify by interlocking visible quartz and feldspar grains, lack of layering, and hardness sufficient to scratch glass. Confirm with a fresh broken surface or hand lens; common worldwide, especially in granitic mountain belts and glacial regions.
