metamorphic

Mica-rich metamorphic rock, probably phyllite or schist

Quartz–mica phyllite/schist, dominated by muscovite or biotite mica and quartz

AI-generated identification · may be incorrect

Gray to silvery-purple, sparkly micaceous surface with fine foliation and irregular cleavage; quartz grains are harder than glass (Mohs 7), while mica is Mohs 2–3. Specific gravity is typically about 2.6–2.8; luster ranges from pearly on mica to vitreous on quartz.

Identified September 2, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or mudstone underwent low- to medium-grade regional metamorphism, causing clay minerals to recrystallize into aligned mica and quartz. Such rocks commonly formed during ancient mountain-building events, though the specimen’s age cannot be determined from the photo.

Uses & applications

Used locally as decorative stone, landscaping material, aggregate, and occasionally architectural facing; attractive polished pieces may be collected, but it is generally not a gemstone.

Geological facts

The glitter comes from reflective mica flakes rather than metallic minerals. Foliation and the tendency to split along planar surfaces distinguish phyllite or schist from ordinary granite.

Field identification & locations

Look for silky or glittery aligned flakes, thin foliation, and a gray-purple weathered color; a knife may scratch mica-rich areas but not quartz grains. Common worldwide in metamorphic belts, including the Appalachians, Rockies, Alps, and Scottish Highlands.