metamorphic

Likely mica-rich schist or pegmatitic quartz-mica rock

Quartz–feldspar–mica aggregate, possibly biotite schist

AI-generated identification · may be incorrect

Hardness is approximately 2.5–7 depending on the visible minerals; it has a dark brown to gray color, glassy quartz and pearly mica luster, and irregular fracture with possible foliation. The pale reflective flakes are likely mica, while darker grains may be biotite, hornblende, or iron oxides.

Identified September 1, 2026More metamorphic →

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Physical properties

Formation & geological history

Probably formed by regional metamorphism of a clay-rich sediment, though a weathered pegmatite is also possible; its geological age cannot be determined from the photograph. Such rocks commonly form in continental mountain belts and Precambrian basement terrains.

Uses & applications

Small pieces are mainly collected as teaching or decorative specimens; schist may be used locally as fill or dimension stone, but this specimen has no evident gem value.

Geological facts

The contrasting sparkly flakes and dark matrix are characteristic of mica-bearing metamorphic rocks. A fresh broken surface, hand lens, and streak or hardness tests would substantially improve identification.

Field identification & locations

Commonly found in metamorphic mountain regions, including the Appalachians, New England, Scandinavia, and parts of the western United States. Test whether flakes split into elastic sheets and whether clear grains scratch glass; avoid assuming a precise species from the image alone.