metamorphic
Greenish-gray slate fragment
Slate; fine-grained metamorphosed mudstone, commonly mica- and chlorite-bearing
AI-generated identification · may be incorrectTypically very fine grained, dull to subtly silky, gray-green, and splits along closely spaced slaty cleavage into thin flat pieces. Hardness is about 3–4 Mohs; crystals are microscopic and specific gravity is roughly 2.7–2.8.
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Physical properties
Typically very fine grained, dull to subtly silky, gray-green, and splits along closely spaced slaty cleavage into thin flat pieces. Hardness is about 3–4 Mohs; crystals are microscopic and specific gravity is roughly 2.7–2.8.
Formation & geological history
Formed when shale or mudstone was subjected to low-grade regional metamorphism, commonly during mountain building. Its exact geological age cannot be determined from the photograph; slate occurs in rocks ranging from Precambrian to recent geologic settings.
Uses & applications
Used for roofing, floor and wall tiles, paving, writing boards, and decorative stone; small fragments have modest collecting value.
Geological facts
The triangular shape appears to be a natural or broken cleavage fragment rather than a diagnostic crystal form. Green coloration commonly reflects chlorite or other low-grade metamorphic minerals.
Field identification & locations
Identify it by its uniform fine texture, planar cleavage, and ability to split into sheets without visible sand grains or large crystals; common localities include Wales, Vermont, Pennsylvania, Spain, and Brazil.
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