igneous
Weathered granite or granitic gneiss
Granite; primarily quartz, feldspar, and mica (possibly foliated as gneiss)
AI-generated identification · may be incorrectCoarse-grained, gray-brown rock with visible interlocking light feldspar/quartz and dark mica or altered minerals; vitreous to dull luster, no obvious cleavage as a whole, and about 6–7 Mohs. Density is typically 2.6–2.8 g/cm³.
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Physical properties
Coarse-grained, gray-brown rock with visible interlocking light feldspar/quartz and dark mica or altered minerals; vitreous to dull luster, no obvious cleavage as a whole, and about 6–7 Mohs. Density is typically 2.6–2.8 g/cm³.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, generally during Precambrian to younger continental mountain-building events; foliation would indicate later metamorphism into granitic gneiss. Surface weathering produces the rounded form and brown staining.
Uses & applications
Widely used as crushed aggregate, road stone, building stone, monuments, countertops, and landscaping rock; this ordinary specimen has little jewelry value.
Geological facts
Granite’s visible texture records slow cooling, allowing large crystals to grow. Brown coloration commonly reflects oxidation of iron-bearing biotite or weathering of feldspar.
Field identification & locations
Identify it by its speckled interlocking crystals and hardness: it should scratch glass and resist a steel knife. Common worldwide in continental shields and mountain belts; a fresh broken surface would distinguish granite from finer-grained basalt or strongly banded gneiss.
