igneous
Diorite (likely a diorite hand specimen)
Diorite, an intrusive intermediate igneous rock composed mainly of plagioclase feldspar and hornblende, with possible biotite or pyroxene
AI-generated identification · may be incorrectCoarse-grained, black-and-white “salt-and-pepper” appearance; typically Mohs hardness about 6–7, vitreous to dull mineral luster, and interlocking crystals without cleavage at the whole-rock scale. The photo shows a specimen on a screen, so its texture and composition cannot be confirmed directly.
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Physical properties
Coarse-grained, black-and-white “salt-and-pepper” appearance; typically Mohs hardness about 6–7, vitreous to dull mineral luster, and interlocking crystals without cleavage at the whole-rock scale. The photo shows a specimen on a screen, so its texture and composition cannot be confirmed directly.
Formation & geological history
Forms when intermediate-composition magma cools slowly underground, allowing visible crystals to grow. Diorite occurs in ancient and geologically young plutons and is not tied to one specific age.
Uses & applications
Used as crushed stone, aggregate, paving material, and dimension stone; polished pieces are sometimes used decoratively.
Geological facts
Its contrasting light feldspar and dark amphibole or biotite grains give it the classic salt-and-pepper look.
Field identification & locations
Look for coarse, interlocking black and white crystals; distinguish it from granite, which usually contains conspicuous quartz, and gabbro, which is darker overall. Found in intrusive bodies worldwide.
