metamorphic
Slate
Slate, a fine-grained metamorphic rock composed mainly of mica-group minerals and quartz
AI-generated identification · may be incorrectTypically gray, fine-grained, dull to silky, and splits into thin sheets along slaty cleavage; hardness is roughly 3–5 Mohs. The pictured surface appears consistent with slate, though mineral composition cannot be confirmed from the image alone.
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Physical properties
Typically gray, fine-grained, dull to silky, and splits into thin sheets along slaty cleavage; hardness is roughly 3–5 Mohs. The pictured surface appears consistent with slate, though mineral composition cannot be confirmed from the image alone.
Formation & geological history
Forms when shale or mudstone is subjected to low-grade metamorphism, producing aligned microscopic minerals. Slate occurs in metamorphic belts of varied geological ages.
Uses & applications
Used for roofing, paving, flooring, blackboards, and decorative stone.
Geological facts
Its planar cleavage allows it to be split into durable, relatively flat slabs.
Field identification & locations
Look for fine grain and smooth, parallel splitting surfaces; common sources include Wales, Vermont, Spain, and parts of China. Typical small specimens or offcuts cost about $5–$30; value depends on size, quality, and provenance.
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