igneous
Lichen-covered granite or granitic gneiss
Granite: quartz + feldspar + mica; possibly gneiss if foliation is confirmed
AI-generated identification · may be incorrectCoarse-grained, speckled gray-pink rock with quartz, feldspar, and dark biotite/hornblende; hardness about 6–7 Mohs, vitreous to pearly mineral luster, no prominent cleavage as a whole, and density roughly 2.6–2.8 g/cm³. The green patch is biological lichen, not part of the rock.
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Physical properties
Coarse-grained, speckled gray-pink rock with quartz, feldspar, and dark biotite/hornblende; hardness about 6–7 Mohs, vitreous to pearly mineral luster, no prominent cleavage as a whole, and density roughly 2.6–2.8 g/cm³. The green patch is biological lichen, not part of the rock.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to younger continental mountain-building events; gneiss forms when such rock is metamorphosed and banded. The exact age and classification require a fresh, lichen-free surface.
Uses & applications
Crushed granite is used for aggregate, road base, monuments, countertops, and building stone; attractive pieces may be collected, but this weathered specimen has little commercial value.
Geological facts
Pink areas are potassium feldspar, white-gray grains are quartz or plagioclase, and black grains are mica or amphibole. Lichen colonization indicates prolonged outdoor exposure and can obscure texture.
Field identification & locations
Identify it by visible interlocking quartz and feldspar grains, dark mica/amphibole, and a scratch resistance near glass; streak is generally white and dilute acid causes no fizz. Common in continental shields, mountain belts, and glacial terrains worldwide.
