metamorphic
Dark gray metamorphic pebble, likely slate or phyllite
Slate/phyllite; chiefly fine-grained quartz, mica, and clay-derived minerals
AI-generated identification · may be incorrectSmooth, dark gray, weakly silky surface with possible foliation and thin pale veins; hardness about 3–6 Mohs depending on composition, opaque, fine-grained, and commonly splits along planar cleavage.
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Physical properties
Smooth, dark gray, weakly silky surface with possible foliation and thin pale veins; hardness about 3–6 Mohs depending on composition, opaque, fine-grained, and commonly splits along planar cleavage.
Formation & geological history
Formed when shale or mudstone underwent low-grade regional metamorphism, typically during mountain building; age depends on source terrain and cannot be determined from the image.
Uses & applications
Commonly used for roofing, floor and wall tiles, paving, and landscaping; attractive polished pieces may be sold as inexpensive decor or collecting specimens.
Geological facts
Slate is the lower-grade equivalent, while phyllite has a more lustrous, wavy foliation from stronger metamorphism. Pale streaks may be quartz or calcite veins.
Field identification & locations
Look for planar layering, a dull-to-silky sheen, and splitting into thin slabs; a streak test and close inspection of cleavage distinguish it from basalt or chert. Common worldwide in metamorphic belts.
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