metamorphic
Dark gray crystalline rock, possibly mica-rich schist or graphite-bearing gneiss
Indeterminate; likely quartz–feldspar–mica metamorphic rock
AI-generated identification · may be incorrectCoarse, irregular fragment with dark gray to black color and reflective cleavage-like surfaces, suggesting abundant mica or graphite. Likely Mohs hardness 2–7 depending on dominant minerals; exact identification requires a close-up, streak, and hardness tests.
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Physical properties
Coarse, irregular fragment with dark gray to black color and reflective cleavage-like surfaces, suggesting abundant mica or graphite. Likely Mohs hardness 2–7 depending on dominant minerals; exact identification requires a close-up, streak, and hardness tests.
Formation & geological history
Probably formed when preexisting shale or felsic rock was subjected to elevated heat and pressure during regional metamorphism, commonly hundreds of millions to billions of years ago.
Uses & applications
Comparable rocks are used as decorative stone, aggregate, roofing material, or landscaping rock; attractive mica-rich pieces may be collected, but this fragment has no evident gemstone value.
Geological facts
Mica produces shiny, platy reflections and splits into thin sheets, while graphite produces a very dark streak and feels unusually greasy. These features can distinguish the specimen from ordinary basalt.
Field identification & locations
Common in metamorphic belts worldwide, including the Appalachians, New England, Canada, Scandinavia, and India. The image is insufficient for a reliable species-level identification; inspect fresh surfaces for layering, test streak, and examine with a hand lens.
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