metamorphic
Dark metamorphic rock, likely biotite schist or gneiss
Quartz–feldspar–biotite metamorphic rock; exact identification requires a fresh surface and testing
AI-generated identification · may be incorrectDark gray-black, fine- to medium-grained, with rusty orange weathering and subtle streaky foliation. Likely hardness 6–7 Mohs, vitreous to dull luster, weak-to-moderate planar fabric, and no obvious cleavage; density commonly 2.7–2.9 g/cm³.
Identified More metamorphic →
Explore Dark metamorphic rock, likely biotite schist or gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-black, fine- to medium-grained, with rusty orange weathering and subtle streaky foliation. Likely hardness 6–7 Mohs, vitreous to dull luster, weak-to-moderate planar fabric, and no obvious cleavage; density commonly 2.7–2.9 g/cm³.
Formation & geological history
Formed when clay-rich sedimentary or igneous rock was buried and subjected to elevated temperature and pressure, recrystallizing quartz, feldspar, and mica during regional metamorphism. Its precise geological age cannot be determined from the photograph.
Uses & applications
Used locally as crushed stone, riprap, landscaping material, and occasionally building stone; attractive foliated pieces are collected but generally have limited gem value.
Geological facts
The orange areas are likely iron-oxide staining from weathering. Fine foliation and mica sheen would support schist or gneiss over basalt, but the image lacks enough detail for a firm distinction.
Field identification & locations
Common in metamorphic belts worldwide, including the Appalachians, Canadian Shield, and Precambrian terrains. Look for aligned mica flakes, banding, and a non-vesicular texture; a streak test, fresh fracture, and hand lens would improve identification.
More like this
