RocksdayAmphibolite vs Gneiss
How to tell them apart
A dark metamorphic rock made mostly of hornblende and plagioclase.
Photo: Karelj, CC BY-SA 3.0
A high-grade metamorphic rock with bold light and dark bands, formed under intense heat and pressure.
Photo: No machine-readable author provided. Siim assumed (based on copyright claims)., CC BY-SA 3.0
Key differences
- Gneiss has light and dark banding.
Side by side
| Property | Amphibolite | Gneiss |
|---|---|---|
| Type | Metamorphic rock | Metamorphic rock |
| Mohs hardness | 5–6 | 6–7 |
| Luster | Vitreous to dull | Granular |
| Colors | Black, Green, White | Gray, White, Black, Pink |
| Crystal system / structure | Medium-grained, often lineated | Coarse, banded |
| Specific gravity | 2.9–3.1 | 2.6–2.9 |
| Found in | Adirondack Mountains, New York; Scottish Highlands | Acasta River, Canada; Outer Hebrides, Scotland |
Properties that are the same for both are grayed out.
How to identify amphibolite
- Black to dark green, sparkly with hornblende.
- Elongated crystals often aligned.
- Heavy.
Structure: Medium-grained, often lineated
Full Amphibolite guide →How to identify gneiss
- Alternating light and dark bands, often wavy.
- Coarse, visible grains.
- Hard; doesn't split into sheets.
- Bands may be folded.
Structure: Coarse, banded
Full Gneiss guide →More comparisons
Could you tell them apart from a blurry close-up?
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