igneous
Diorite
Intermediate intrusive igneous rock
Hardness of 6-7 on the Mohs scale, color ranges from dark gray to black and white speckled ('salt and pepper' appearance), sub-to-euhedral crystal structure, vitreous to dull luster, specific gravity of 2.8-3.0.
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Physical properties
Hardness of 6-7 on the Mohs scale, color ranges from dark gray to black and white speckled ('salt and pepper' appearance), sub-to-euhedral crystal structure, vitreous to dull luster, specific gravity of 2.8-3.0.
Formation & geological history
Forms from the slow cooling of magma beneath the Earth's surface, possessing an intermediate composition between basalt and granite. Often associated with convergent plate boundaries and subduction zones.
Uses & applications
Commonly used in construction as crushed stone for road base, aggregate, and building stone. Also used as dimension stone in architecture and sometimes as a polishing stone.
Geological facts
Historically, ancient civilizations such as the Egyptians and Mesopotamians used diorite for statues and vessels due to its extreme toughness and resistance to weathering.
Field identification & locations
Easily identified in the field by its distinct speckled black and white texture caused by a mix of plagioclase feldspar and dark minerals like hornblende and biotite.
