igneous
Granite
Granite (Intrusive Igneous Rock)
Hardness of 6 on the Mohs scale, typically gray, pink, or white in color depending on its feldspar content, vitreous to dull luster, phaneritic (coarse-grained) crystal structure, specific gravity around 2.65 to 2.75.
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Physical properties
Hardness of 6 on the Mohs scale, typically gray, pink, or white in color depending on its feldspar content, vitreous to dull luster, phaneritic (coarse-grained) crystal structure, specific gravity around 2.65 to 2.75.
Formation & geological history
Formed from the slow cooling of magma rich in silica and alkali metal oxides beneath the Earth's surface. The Harney Peak granite of Mount Rushmore is approximately 1.7 billion years old (Paleoproterozoic era).
Uses & applications
Used extensively in monumental architecture, construction, countertops, flooring, and landscaping.
Geological facts
Mount Rushmore features the faces of U.S. presidents carved directly into the Harney Peak granite formation of the Black Hills in South Dakota.
Field identification & locations
Easily identified by its interlocking visible mineral grains of quartz, alkali feldspar, and plagioclase. Found extensively in continental shields and mountain ranges worldwide.
