igneous
Granite (Water-worn Pebble/Cobble)
Granite (Plutonic felsic intrusive rock)
AI-generated identification · may be incorrectHardness 6-7 on Mohs scale; color is mottled pink, white, grey, and black; phaneritic (coarse-grained) texture with visible interlocked crystals; vitreous to pearly luster on mineral faces; specific gravity approximately 2.65-2.75 g/cm³.
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Physical properties
Hardness 6-7 on Mohs scale; color is mottled pink, white, grey, and black; phaneritic (coarse-grained) texture with visible interlocked crystals; vitreous to pearly luster on mineral faces; specific gravity approximately 2.65-2.75 g/cm³.
Formation & geological history
Formed deep within the Earth's crust by the slow cooling and crystallization of silica-rich felsic magma. This specific specimen has been subsequentely weathered, rounded, and smoothed by glacial, fluvial, or wave action into a cobble.
Uses & applications
Widely quarried for building stones, countertops, curbing, paving, and crushed aggregate for roads and rail ballast. Rounded pebbles are also used for landscaping and garden decoration.
Geological facts
Granite makes up a major portion of Earth's continental crust. Its pinkish hue typically comes from potassium feldspar (orthoclase or microcline), white to grey from plagioclase feldspar and quartz, and dark flecks from biotite mica or hornblende.
Field identification & locations
Easily identified by its granular texture containing interlocking crystals of quartz (glassy, grey/clear), feldspar (pink and opaque white), and dark mica or amphibole flakes. Common worldwide in riverbeds, beaches, and glacial till deposits.
