metamorphic
Weathered schist or phyllite
Mica schist/phyllite, likely quartz–mica-rich metamorphic rock
AI-generated identification · may be incorrectFine to medium grained, gray-brown and rusty from surface oxidation, with visible planar foliation and platy cleavage. Typical hardness is about 2–3 for mica surfaces and 6–7 for quartz; luster ranges dull to silky or micaceous, with specific gravity around 2.6–2.8.
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Physical properties
Fine to medium grained, gray-brown and rusty from surface oxidation, with visible planar foliation and platy cleavage. Typical hardness is about 2–3 for mica surfaces and 6–7 for quartz; luster ranges dull to silky or micaceous, with specific gravity around 2.6–2.8.
Formation & geological history
Formed when shale or mudstone underwent low- to medium-grade regional metamorphism, recrystallizing clay minerals into mica and aligning them under pressure. Its exact geological age cannot be determined from the photograph; such rocks occur in ancient mountain belts worldwide.
Uses & applications
Used locally as building stone, landscaping rock, riprap, and occasionally wall or roofing slate when cleavage is strong. Ordinary weathered specimens generally have little commercial or collector value.
Geological facts
The rusty orange patches are likely iron-oxide weathering, while the layered texture reflects metamorphic foliation rather than sedimentary bedding.
Field identification & locations
Identify it by its planar layers, tendency to split along foliation, sparkly mica flakes, and lack of vesicles or rounded grains; a fresh broken surface and acid, streak, or hardness tests would improve identification. Common in metamorphic terrains such as the Appalachians, New England, Scotland, and many mountain belts.
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