igneous
Lichen-covered granite
Granite, chiefly quartz–feldspar–mica; surface colonized by lichens
AI-generated identification · may be incorrectCoarse-grained, pinkish-gray rock with black and white mineral grains; quartz and feldspar give a glassy to dull luster, while biotite/hornblende form dark patches. Hardness is approximately 6–7 Mohs, with no visible foliation and irregular fracture; lichen obscures much of the texture.
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Physical properties
Coarse-grained, pinkish-gray rock with black and white mineral grains; quartz and feldspar give a glassy to dull luster, while biotite/hornblende form dark patches. Hardness is approximately 6–7 Mohs, with no visible foliation and irregular fracture; lichen obscures much of the texture.
Formation & geological history
A felsic intrusive igneous rock formed by slow crystallization of silica-rich magma deep in the continental crust, commonly during Precambrian to Phanerozoic geologic events. The weathered surface and dark growths are biological, not part of the original mineral assemblage.
Uses & applications
Widely used as dimension stone, building facades, monuments, countertops, paving, and aggregate; attractive pieces may be collected but are generally low value.
Geological facts
Typical composition is quartz, potassium feldspar, plagioclase, and minor biotite or hornblende. The mottled appearance results from both mineral variation and crustose lichens growing on the exposed surface.
Field identification & locations
Identify it by interlocking visible crystals, abundant light feldspar/quartz, and scattered black mica or amphibole; a fresh broken area will show the true grain and color. Common worldwide in continental shields, mountain batholiths, and exposed bedrock.
