igneous
Granite cobble
Granite; primarily quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, speckled gray-white rock with black mica or amphibole; crystalline texture, vitreous to dull luster, no prominent cleavage as a whole, Mohs hardness about 6–7, specific gravity 2.63–2.75.
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Physical properties
Coarse-grained, speckled gray-white rock with black mica or amphibole; crystalline texture, vitreous to dull luster, no prominent cleavage as a whole, Mohs hardness about 6–7, specific gravity 2.63–2.75.
Formation & geological history
Intrusive igneous rock formed by slow cooling of silica-rich magma deep in Earth’s crust, commonly during Precambrian to Phanerozoic plutonic events. The rounded shape indicates later erosion and transport, or human shaping.
Uses & applications
Widely used for building stone, monuments, countertops, paving, aggregate, and landscaping; this small specimen has modest educational or decorative value.
Geological facts
Individual crystals are interlocking and visible without magnification, distinguishing granite from fine-grained volcanic rocks. Exact composition may vary toward granodiorite.
Field identification & locations
Identify it by its visible quartz and feldspar grains, granular texture, and gray/pink/white coloration; it is common in continental crust and glacial or river gravels worldwide. A streak test is usually unhelpful.
