metamorphic

Banded amphibolite (hornblende-rich metamorphic rock)

Amphibolite; predominantly hornblende ± plagioclase, with possible biotite and quartz

AI-generated identification · may be incorrect

Dark greenish-black, fine- to medium-grained, weakly foliated and elongated, with a dull to subtly vitreous luster; typical hardness is about 5–6 Mohs and specific gravity roughly 3.0–3.4. The apparent pinkish vein or band may be feldspar, quartz, or alteration material.

Identified September 10, 2026More metamorphic →

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At a glance

Common name: Banded amphibolite (hornblende-rich metamorphic rock)
Scientific name: Amphibolite; predominantly hornblende ± plagioclase, with possible biotite and quartz
Category: metamorphic
Identified: September 10, 2026
Method: Standard

AI Estimated Value

About $5–$25 for a common tumbled or hand specimen; $25–$75 for an unusually attractive polished or strongly banded piece.

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

Forms when basaltic or gabbroic protoliths undergo medium- to high-grade regional metamorphism, commonly during mountain building; specimens may range from Precambrian to younger Paleozoic–Mesozoic ages. The rounded shape indicates natural wear or deliberate polishing/tumbling.

Uses & applications

Used as crushed stone, aggregate, riprap, dimension stone, and occasionally decorative material; attractive pieces are collected but rarely used as gemstones.

Geological facts

Amphibolite commonly preserves metamorphic foliation and elongated hornblende crystals, distinguishing it from uniformly dark basalt. Exact identification requires a fresh surface, hardness testing, and ideally thin-section or mineralogical analysis.

Field identification & locations

Look for dense dark rock with aligned amphibole grains, weak layering, and little vesicularity; common in metamorphic belts worldwide. Avoid identifying solely by color because dark gneiss, basalt, serpentinite, and schist can look similar.