metamorphic

Weathered metamorphic rock, likely mica schist or gneiss

Quartz–feldspar–mica schist/gneiss; exact identification is uncertain from the photograph

AI-generated identification · may be incorrect

Gray to tan, coarse-grained, foliated texture with shiny dark mica-rich patches and pale quartz/feldspar. Typical hardness is about 2–7 depending on mineral tested; mica has perfect cleavage, while quartz and feldspar are harder with vitreous to dull luster.

Identified September 6, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when preexisting sedimentary or igneous rock was buried and subjected to elevated heat and pressure, producing foliation and mineral recrystallization. Its age cannot be determined visually and may range from Precambrian to much younger depending on locality.

Uses & applications

Used locally as dimension stone, wall stone, landscaping material, and aggregate; attractive pieces may be cut or polished, though this specimen appears mainly a field or teaching sample.

Geological facts

The glittering surfaces likely reflect mica, while pale irregular grains are probably quartz and feldspar. Strong planar layering or easy splitting would favor schist; more massive, banded texture would favor gneiss.

Field identification & locations

Look for aligned mica flakes, foliation, and a lack of vesicles or fossils; a streak test, hardness tests, and thin-section examination would refine identification. Common in regional metamorphic belts worldwide.