metamorphic

Pyrite-rich schist or phyllite

Quartz–mica schist/phyllite with disseminated pyrite (FeS₂)

AI-generated identification · may be incorrect

Fine-grained, foliated, gray-brown specimen with abundant brassy metallic flakes; likely quartz, mica, and pyrite. Pyrite hardness is 6–6.5 Mohs, cubic crystal structure, metallic luster, and poor cleavage; matrix hardness is variable.

Identified September 17, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or mudstone underwent low- to medium-grade regional metamorphism, recrystallizing clay minerals into mica and concentrating sulfides. Such rocks commonly formed during ancient mountain-building events, but the exact age cannot be determined from the image.

Uses & applications

Primarily a collector specimen or indicator of sulfide mineralization; it has little construction value at this size. Pyrite may be recovered for sulfur or mineral collecting, while schist can occasionally be used as decorative stone.

Geological facts

The brassy grains are probably pyrite, often called “fool’s gold,” rather than gold. Pyrite produces a dark greenish-black streak, whereas gold leaves a yellow streak and is much softer.

Field identification & locations

Look for foliation, sparkly mica-like surfaces, and hard, brassy grains that resist scratching; a streak test, hardness test, and acid test would improve identification. Common in metamorphic belts worldwide, including the Appalachians, Andes, Alps, and Precambrian terrains.