metamorphic
Slate or shale fragment
Slate; predominantly clay minerals, mica, and quartz (low-grade metamorphosed shale)
AI-generated identification · may be incorrectDark gray to black, dull to slightly silky, fine-grained, with strong planar cleavage and thin platy fracture; hardness about 2.5–4 Mohs, generally low to moderate specific gravity. The surrounding rounded pebbles are mostly weathered river stones, but the central specimen is the clearest target.
Identified More metamorphic →
Explore Slate or shale fragment in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, dull to slightly silky, fine-grained, with strong planar cleavage and thin platy fracture; hardness about 2.5–4 Mohs, generally low to moderate specific gravity. The surrounding rounded pebbles are mostly weathered river stones, but the central specimen is the clearest target.
Formation & geological history
Slate forms when shale or mudstone is compressed and weakly metamorphosed during mountain-building, commonly from Paleozoic to younger sedimentary protoliths. It typically occurs in folded metamorphic belts and is released as angular fragments by weathering.
Uses & applications
Used for roofing, floor and wall tiles, paving, blackboards, landscaping, and occasionally lapidary work; this beach fragment has little commercial value.
Geological facts
Slate’s defining feature is slaty cleavage, produced by aligned microscopic mica and clay minerals rather than original bedding. It can split into relatively flat sheets, unlike most massive mudstones.
Field identification & locations
Identify it by its charcoal color, very fine texture, and repeated splitting along flat planes; a steel nail may scratch it. Common sources include Wales, Vermont, Spain, Portugal, and metamorphic coastal or river gravels.
More like this
