igneous
Weathered coarse-grained igneous rock, likely diorite or gabbro
Diorite–gabbro compositional range; chiefly plagioclase feldspar, amphibole/pyroxene, and minor biotite or quartz
AI-generated identification · may be incorrectDark gray-brown, mottled, granular texture with subhedral interlocking crystals and dull to slightly vitreous luster; individual mineral hardness is generally Mohs 5–7, with no obvious cleavage on the weathered surface. Specific gravity is approximately 2.7–3.1.
Identified More igneous →
Explore Weathered coarse-grained igneous rock, likely diorite or gabbro in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-brown, mottled, granular texture with subhedral interlocking crystals and dull to slightly vitreous luster; individual mineral hardness is generally Mohs 5–7, with no obvious cleavage on the weathered surface. Specific gravity is approximately 2.7–3.1.
Formation & geological history
Likely a slowly cooled intrusive igneous rock formed when magma crystallized underground during ancient geologic time, then became exposed and rounded by weathering and transport. Exact age and locality cannot be determined from the photograph.
Uses & applications
Used as crushed aggregate, road stone, riprap, dimension stone, and occasionally polished architectural stone; generally has little gemstone value.
Geological facts
The specimen’s rounded shape and iron-brown surface staining indicate prolonged weathering or stream/beach transport. A fresh broken surface would better distinguish diorite from gabbro, granite, or metamorphic alternatives.
Field identification & locations
Look for visible interlocking crystals, a salt-and-pepper appearance, and a lack of layering or foliation; a streak test is unhelpful, while a fresh surface and hand lens are useful. Common worldwide in exposed intrusive complexes and gravel deposits.
