metamorphic
Dark slate fragment
Slate, a fine-grained metamorphic rock composed chiefly of quartz, mica, and chlorite
AI-generated identification · may be incorrectDark gray to black, dull to slightly silky; very fine-grained with slaty cleavage. Hardness is typically about 3–4 on Mohs; crystal structure is too fine to distinguish by eye.
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Physical properties
Dark gray to black, dull to slightly silky; very fine-grained with slaty cleavage. Hardness is typically about 3–4 on Mohs; crystal structure is too fine to distinguish by eye.
Formation & geological history
Forms when shale or mudstone is compressed and mildly metamorphosed, developing flat cleavage; commonly dates from Paleozoic or younger regional metamorphism.
Uses & applications
Slate is used for roofing, flooring, paving, and writing tablets; this small rough fragment has little commercial value.
Geological facts
Its characteristic tendency to split into thin, flat sheets reflects aligned microscopic minerals.
Field identification & locations
Look for a fine, uniform texture and flat splitting surfaces; slate occurs in metamorphic belts worldwide, including Wales, Spain, and the northeastern United States.
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