igneous
Granite (Pebble)
Intrusive Felsic Igneous Rock
Hardness 6-7 Mohs, mottled reddish-brown/tan and black color, dull to vitreous luster, phaneritic texture composed of intergrown quartz, feldspar, and mafic minerals such as biotite or hornblende. Specific gravity approx 2.65-2.75.
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Physical properties
Hardness 6-7 Mohs, mottled reddish-brown/tan and black color, dull to vitreous luster, phaneritic texture composed of intergrown quartz, feldspar, and mafic minerals such as biotite or hornblende. Specific gravity approx 2.65-2.75.
Formation & geological history
Formed by the slow crystallization of felsic magma beneath the Earth's surface over millions of years. This specimen is a stream- or beach-rounded pebble shaped through erosion and transport.
Uses & applications
Used extensively as dimension stone, architectural facings, counter tops, crushed stone for aggregate, and as a popular subject for lapidary tumbling and rock collecting.
Geological facts
Granite makes up a large portion of Earth's continental crust. The distinct speckled texture ('salt-and-pepper' or pink/black pattern) comes from individual mineral grains cooling slowly deep underground.
Field identification & locations
Identified in the field by its coarse-grained interlocking mineral texture, hardness (scratches steel), and characteristic mix of pink/tan feldspar and dark amphibole/biotite. Found globally in continental plutonic settings, riverbeds, and gravel deposits.
