metamorphic
Weathered gray metamorphic rock, likely phyllite or slate
Micaceous quartz–phyllosilicate rock; commonly quartz + muscovite/illite ± chlorite
AI-generated identification · may be incorrectTypically gray to tan, fine-grained, with silky to dull luster and weakly developed foliation or cleavage; hardness about 3–6 Mohs depending on mica content. The image shows weathered, foliated material, but exact identification requires a fresh surface and tests.
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Physical properties
Typically gray to tan, fine-grained, with silky to dull luster and weakly developed foliation or cleavage; hardness about 3–6 Mohs depending on mica content. The image shows weathered, foliated material, but exact identification requires a fresh surface and tests.
Formation & geological history
Formed when shale or mudstone underwent low-grade regional metamorphism during mountain building; age depends on locality and may range from Paleozoic to Precambrian. Weathering has produced the tan-brown surface staining.
Uses & applications
Used locally as flagstone, roofing or landscaping stone, and aggregate; attractive pieces may be collected, but it is generally not a jewelry material.
Geological facts
Phyllite lies texturally between slate and schist and commonly displays a characteristic silky sheen from aligned mica. Rust-colored patches are likely iron-oxide weathering.
Field identification & locations
Look for planar splitting, aligned mica sheen, and a fine-grained texture; slate splits more cleanly, while schist has visibly larger mica crystals. Common in metamorphic belts worldwide, including the Appalachians and New England.
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