Granite (Pebble)

Hardness 6-7 on Mohs scale. Mottled pink, gray, white, and black coloration with a vitreous to dull dull-subvitreous luster. Coarse-grained phaneritic texture composed primarily of potassium feldspar, quartz, and minor plagioclase, biotite, or amphibole. Formed from intrusive magmatic cooling and subsequent stream/glacial erosion rounding.

Formed beneath the Earth's surface through the slow cooling and crystallization of felsic magma. Many stream-rounded or beach-rounded pebbles originate from eroded Precambrian granite shields or mountain ranges.

Widely used as coarse aggregate in construction, landscaping, road base, and dimension stone for countertops and monuments. Smooth stream pebbles are collected for decorative aquariums, crafts, and rock tumbling.

Granite makes up a large portion of Earth's continental crust. The pink hue seen in this specimen is caused by orthoclase (potassium-rich feldspar), while the translucent grayish areas are quartz grains.

Identify by looking for intergrown grains of pink/white feldspar, glassy quartz, and dark mica or hornblende crystals in a water-worn, smooth pebble shape. Extremely common along riverbeds, lakeshores, and glacial till.