metamorphic

Feldspathic gneiss (likely augen gneiss)

Quartz–feldspar–mica gneiss; commonly dominated by quartz, K-feldspar/plagioclase, and biotite

AI-generated identification · may be incorrect

Coarse-grained, strongly foliated rock with pale pink feldspar, gray quartz, and dark mica/amphibole bands; vitreous quartz luster and feldspar cleavage. Typical hardness is about 6–7 Mohs, with no single crystal structure because it is a polymineralic rock.

Identified September 15, 2026More metamorphic →

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At a glance

Common name: Feldspathic gneiss (likely augen gneiss)
Scientific name: Quartz–feldspar–mica gneiss; commonly dominated by quartz, K-feldspar/plagioclase, and biotite
Category: metamorphic
Identified: September 15, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a hand-sized common specimen; $30–$150+ for unusually attractive, polished, or provenance-documented pieces.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Formed when granitic or volcanic protoliths underwent high-grade regional metamorphism, producing compositional banding and stretched feldspar “eyes.” Such rocks commonly formed during Precambrian to Paleozoic mountain-building events.

Uses & applications

Used as crushed stone, dimension stone, landscaping rock, and occasionally as decorative slabs; attractive pieces are collected but generally have modest value.

Geological facts

The irregular light-colored patches and streaks are characteristic of gneissic segregation and deformation, distinguishing it from uniformly crystalline granite.

Field identification & locations

Identify it by alternating light and dark mineral bands, coarse grains, and a fractured rather than uniformly granular texture; common in ancient continental shields and mountain belts worldwide. The photograph alone cannot confirm exact subtype.