metamorphic
Dark metamorphic rock, likely schist or amphibolite
Biotite–quartz schist / amphibolite (tentative; image alone is insufficient for exact identification)
AI-generated identification · may be incorrectGray-black, coarse and strongly foliated, with mica-like reflective surfaces and possible quartz or feldspar patches; likely Mohs hardness 5–6, vitreous to pearly luster, and weak-to-moderate cleavage along foliation. Specific gravity is approximately 2.7–3.2.
Identified More metamorphic →
Explore Dark metamorphic rock, likely schist or amphibolite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Gray-black, coarse and strongly foliated, with mica-like reflective surfaces and possible quartz or feldspar patches; likely Mohs hardness 5–6, vitreous to pearly luster, and weak-to-moderate cleavage along foliation. Specific gravity is approximately 2.7–3.2.
Formation & geological history
Formed when shale or basaltic protoliths were subjected to elevated temperature and pressure during regional metamorphism, commonly in Precambrian to Paleozoic mountain belts. The irregular texture suggests deformation and recrystallization.
Uses & applications
Used locally as crushed stone, riprap, or landscaping material; attractive polished pieces may be collected, though this specimen appears more valued as a field sample than as a gemstone.
Geological facts
Strong foliation and sparkling mica distinguish it from ordinary basalt; rusty patches may represent oxidation of iron-bearing minerals such as biotite or pyrite.
Field identification & locations
Common in metamorphic terranes worldwide, including the Appalachian, Canadian Shield, and European mountain belts. Check for aligned mica layers, streaky banding, and whether a steel knife scratches lighter grains; a fresh broken surface and hand lens would improve identification.
More like this
