metamorphic

Granite-like gneiss

Foliated granitic gneiss, composed mainly of quartz, feldspar, and mica

AI-generated identification · may be incorrect

Medium- to coarse-grained, gray-green, with subtle foliation and scattered pale feldspar/quartz grains; vitreous quartz, pearly mica, hardness about 6–7 Mohs, no obvious cleavage as a whole, and specific gravity roughly 2.6–2.8.

Identified September 17, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when granitic or sedimentary protolith was subjected to high temperature and pressure, producing recrystallization and weak banding; commonly Precambrian to younger in age.

Uses & applications

Used as dimension stone, facing slabs, aggregate, landscaping rock, and building material; attractive pieces may be polished for architectural use, but this specimen has modest gem-collector value.

Geological facts

Gneiss is identified by mineral segregation or foliation rather than by a strongly layered sedimentary texture; the pictured piece may also be a foliated granite or granitic metamorphic rock.

Field identification & locations

Look for interlocking quartz and feldspar, dark mica/hornblende, and compositional streaking; common in ancient continental shields and metamorphic mountain belts worldwide. A fresh surface and hand lens help distinguish it from granite.