igneous
Granite Glacial Cobble
Granite
Hardness 6-7 on Mohs scale. Colors range from grey to pinkish and white due to potassium feldspar, plagioclase feldspar, and quartz composition. Luster is dull to vitreous, with a coarse phaneritic texture.
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Physical properties
Hardness 6-7 on Mohs scale. Colors range from grey to pinkish and white due to potassium feldspar, plagioclase feldspar, and quartz composition. Luster is dull to vitreous, with a coarse phaneritic texture.
Formation & geological history
Formed from the slow cooling and crystallization of felsic magma deep beneath the Earth's surface. These specific rounded boulders were shaped and transported by glacial activity during the Pleistocene epoch.
Uses & applications
Commonly used for landscaping, retainment, rock gardens, decorative garden borders, and general construction aggregate.
Geological facts
Glacial erratics and cobbles can travel hundreds of miles from their original bedrock source via movement within ice sheets.
Field identification & locations
Look for a salt-and-pepper appearance with visible interlocking crystals of quartz, feldspar, and dark minerals like mica or amphibole. Extensively available in glaciated regions of North America and Europe.
