igneous
Dark gray crystalline rock, likely diorite or gabbro
Coarse-grained mafic/intermediate intrusive rock; commonly plagioclase feldspar + amphibole/pyroxene, with possible biotite
AI-generated identification · may be incorrectHardness about 6–7 Mohs; dark gray, granular texture, subvitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock. The photograph cannot reliably distinguish diorite from gabbro or amphibolite.
Identified More igneous →
Explore Dark gray crystalline rock, likely diorite or gabbro in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 6–7 Mohs; dark gray, granular texture, subvitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock. The photograph cannot reliably distinguish diorite from gabbro or amphibolite.
Formation & geological history
Formed when magma slowly cooled beneath Earth’s surface, producing visible crystals; typically Paleozoic to Precambrian in exposed terrains, though intrusive bodies occur throughout geologic time.
Uses & applications
Used as crushed aggregate, road base, riprap, building stone, and occasionally countertops or decorative stone; ordinary hand specimens have little commercial value.
Geological facts
Diorite is intermediate in composition, whereas darker gabbro is compositionally equivalent to basalt but coarse-grained. Surface weathering and lighting can make either appear nearly black.
Field identification & locations
Look for interlocking light plagioclase and dark amphibole/pyroxene grains; a fresh broken surface is more diagnostic than the weathered exterior. Common worldwide in plutons and continental mountain belts.
