metamorphic

Banded gneiss (likely weathered orthogneiss)

Gneiss; predominantly quartz–feldspar–mica, with possible iron-oxide staining

AI-generated identification · may be incorrect

Hardness about 6–7 Mohs; tan, gray, and rusty-brown bands; generally dull to slightly sparkly. Coarse-grained, foliated texture with compositional banding and no prominent cleavage; specific gravity roughly 2.6–2.8.

Identified September 2, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when granite or other crustal rock underwent intense heat and pressure, segregating minerals into light and dark bands. Typical ages range from hundreds of millions to several billion years, depending on its source terrane.

Uses & applications

Used locally as dimension stone, landscaping rock, aggregate, and decorative slabs; attractive pieces are collected but are usually low-value.

Geological facts

The sweeping layers reflect metamorphic foliation rather than sedimentary bedding. Rusty colors commonly result from oxidation of iron-bearing minerals such as biotite or sulfides.

Field identification & locations

Identify it by its hard, interlocking quartz-feldspar grains and alternating light/dark mineral bands; it should resist scratching by a steel knife. Common in ancient continental shields and metamorphic mountain belts, including the Appalachians, Canadian Shield, Scandinavia, and India.