igneous
Diorite
Diorite
Phaneritic (coarse-grained) texture; Mohs hardness of 6 to 7; salt-and-pepper black and white color; vitreous to dull luster; specific gravity of 2.8 to 3.0. Composed mainly of plagioclase feldspar, hornblende, and biotite.
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Physical properties
Phaneritic (coarse-grained) texture; Mohs hardness of 6 to 7; salt-and-pepper black and white color; vitreous to dull luster; specific gravity of 2.8 to 3.0. Composed mainly of plagioclase feldspar, hornblende, and biotite.
Formation & geological history
Formed by the slow cooling and crystallization of intermediate magma deep within the Earth's crust, typically in subduction zone environments above convergent plate boundaries.
Uses & applications
Used in construction as crushed stone or dimension stone, for paving, statues, and architectural features. Historically used for ancient carvings due to its durability.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia to carve hard sculptures and inscriptions, including the famous Code of Hammurabi stele.
Field identification & locations
Identified by its distinctive coarse-grained, black-and-white 'salt-and-pepper' speckled appearance containing roughly equal amounts of light plagioclase and dark mafic minerals. Found widely in volcanic arcs and mountain roots.
