igneous
Weathered granite boulder
Granite; chiefly quartz, plagioclase and potassium feldspar, with minor biotite/hornblende
AI-generated identification · may be incorrectTypically coarse-grained, gray and speckled, with a granular texture and glassy-to-dull luster; Mohs hardness about 6–7, massive with no regular cleavage as a rock, and specific gravity about 2.63–2.75. The image shows a rounded, weathered surface, though individual grains are not clearly resolvable.
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Physical properties
Typically coarse-grained, gray and speckled, with a granular texture and glassy-to-dull luster; Mohs hardness about 6–7, massive with no regular cleavage as a rock, and specific gravity about 2.63–2.75. The image shows a rounded, weathered surface, though individual grains are not clearly resolvable.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic mountain-building events; this boulder was likely exposed by erosion or glacial transport. Surface rounding and discoloration reflect weathering.
Uses & applications
Used extensively as dimension stone, monuments, countertops, curbs, building aggregate and landscaping rock; attractive polished varieties are also used decoratively.
Geological facts
Granite’s visible interlocking crystals record slow underground cooling. It commonly weathers into rounded “corestones” through spheroidal weathering along fractures.
Field identification & locations
Identify it by coarse interlocking light and dark grains, quartz’s glassy appearance, feldspar’s pale blocky grains, and resistance to scratching by steel. Common worldwide, especially in continental shields and mountain belts; the exact locality cannot be determined from the image.
