metamorphic
Raw dark metamorphic rock, likely schist or slate
Mica schist or phyllite; commonly quartz–mica–chlorite aggregate
AI-generated identification · may be incorrectDark gray to brown, fine-grained and foliated with layered surfaces and a dull to slightly silky luster. Typical hardness is about 2–4 Mohs, with visible cleavage or splitting along foliation; exact identification requires testing and a fresh surface.
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Physical properties
Dark gray to brown, fine-grained and foliated with layered surfaces and a dull to slightly silky luster. Typical hardness is about 2–4 Mohs, with visible cleavage or splitting along foliation; exact identification requires testing and a fresh surface.
Formation & geological history
Formed when shale or mudstone was subjected to regional heat and pressure during mountain building, generally from Paleozoic to Precambrian terrains. The specimen appears naturally weathered and may contain iron-oxide staining.
Uses & applications
Used locally as dimension stone, roofing or landscaping material; attractive pieces may be kept as geological specimens, but this small rough fragment has little gem value.
Geological facts
The layered texture reflects alignment of microscopic clay minerals and mica. Phyllite has a satin sheen, while schist shows larger visible mica flakes; the image is not sufficiently diagnostic to separate them confidently.
Field identification & locations
Look for persistent planar layers, a platy break, and a streak or flakes of mica; it is unlike a crystal or meteorite because of its strong foliation. Common worldwide in metamorphic mountain belts.
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