igneous
Diorite
Diorite, a coarse-grained intermediate intrusive igneous rock composed mainly of plagioclase feldspar and hornblende, with minor biotite, pyroxene, and quartz.
AI-generated identification · may be incorrectTypically dark gray-green with a salt-and-pepper texture, granular luster, and interlocking crystals; Mohs hardness is about 6–7, with no prominent cleavage as a rock and specific gravity around 2.7–2.9.
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Physical properties
Typically dark gray-green with a salt-and-pepper texture, granular luster, and interlocking crystals; Mohs hardness is about 6–7, with no prominent cleavage as a rock and specific gravity around 2.7–2.9.
Formation & geological history
Forms when intermediate-composition magma cools slowly underground, producing visible crystals; specimens may range from Precambrian to much younger ages. The image is consistent with diorite, though precise identification requires fresh surface and mineral testing.
Uses & applications
Used as crushed aggregate, road stone, dimension stone, paving, and occasionally countertops or monuments; it has limited gemstone value.
Geological facts
Diorite lies compositionally between granite and gabbro and commonly displays a distinctive black-and-white or greenish salt-and-pepper appearance.
Field identification & locations
Common in continental plutons, volcanic-arc batholiths, and mountain belts worldwide. Identify it by its coarse interlocking grains, abundant pale plagioclase, and dark amphibole/biotite; unlike granite, it has little visible quartz or pink feldspar.
