igneous
Rounded granite (glacial cobble)
Granite; chiefly quartz, alkali feldspar, plagioclase, and mica/amphibole
AI-generated identification · may be incorrectCoarse-grained, speckled gray-pink rock with a granular texture and low-glassy luster; individual minerals are interlocking and lack cleavage as a whole. Typical hardness is about 6–7 Mohs and specific gravity 2.6–2.7.
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Physical properties
Coarse-grained, speckled gray-pink rock with a granular texture and low-glassy luster; individual minerals are interlocking and lack cleavage as a whole. Typical hardness is about 6–7 Mohs and specific gravity 2.6–2.7.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic mountain-building. Its smooth, elongated shape likely resulted from glacial transport and abrasion or stream rolling.
Uses & applications
Used as building stone, paving, countertops, monuments, aggregate, and landscape stone; this rounded specimen has mainly educational or decorative value.
Geological facts
The pink grains are potassium feldspar, gray translucent grains are quartz, and dark flakes or patches are biotite, hornblende, or other mafic minerals. Granite’s visible crystals indicate slow underground cooling.
Field identification & locations
Identify it by visible interlocking quartz and feldspar grains, pink-gray color, and lack of layering or foliation; common in continental shield regions and glacial deposits. Approximate value: $2–$15 as a common cobble, or $20–$75 if unusually attractive and sold as a display specimen.
