igneous
Coarse-grained granite or granitic gneiss
Granite; predominantly quartz, potassium feldspar, plagioclase, and dark biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pink, gray, cream, and black mottling with a granular, crystalline texture and generally vitreous-to-dull luster. The irregular banding or streaking may indicate weak gneissic foliation; cleavage occurs in feldspars, not as a whole rock.
Identified More igneous →
Explore Coarse-grained granite or granitic gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 6–7 Mohs; pink, gray, cream, and black mottling with a granular, crystalline texture and generally vitreous-to-dull luster. The irregular banding or streaking may indicate weak gneissic foliation; cleavage occurs in feldspars, not as a whole rock.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the continental crust, then exposed by uplift and erosion; comparable granites range from Precambrian to younger Phanerozoic ages. If strongly banded, it may be metamorphosed granite (gneiss).
Uses & applications
Used as dimension stone, countertops, monuments, aggregate, and decorative landscaping rock; attractive pieces may be polished for display.
Geological facts
Quartz appears glassy gray, feldspar commonly produces the pink or cream areas, and biotite or hornblende forms black grains. A fresh broken surface should reveal interlocking crystals rather than sedimentary layers.
Field identification & locations
Common worldwide in continental mountain belts, including the Sierra Nevada, Appalachians, Canadian Shield, and Scandinavian Shield. A hand lens, streak-free hardness testing, and inspection for visible interlocking crystals help distinguish it from sandstone or concrete.
