Comparison · Metamorphic Rocks vs Igneous Rocks
Amphibolite vs Gabbro
Amphibolite and Gabbro are easy to confuse. Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Amphibolite and Gabbro
- Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Luster is different: Amphibolite is dull while Gabbro is dull to vitreous (in crystals).
- Hold a thin edge to the light: Amphibolite is opaque, Gabbro is Opaque.
- They overlap in black, green, gray, and white, but Amphibolite also comes in red and Gabbro also comes in multicolored.
Amphibolite vs Gabbro properties
| Property | Amphibolite | Gabbro |
|---|---|---|
| Type | Metamorphic Rocks | Igneous Rocks |
| Mohs hardness | 5.5 | 5–6.5 |
| Luster | dull | Dull to vitreous (in crystals) |
| Streak | Variable; usually pale gray to white | — |
| Transparency | opaque | Opaque |
| Specific gravity | 3 | 2.9–3.1 |
| Crystal system | varies | — |
| Common colors | Black, Dark green, Gray, White, Red | Dark gray, Black, Greenish black, Speckled black and white |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Amphibolite and Gabbro trade in a similar range, around $10.
About Amphibolite
Amphibolite is a dark, tough metamorphic rock made mostly of amphibole and plagioclase. It often appears black to dark green and may contain red garnets.
About Gabbro
Gabbro is a coarse-grained, dark-colored intrusive igneous rock composed mainly of calcium-rich plagioclase feldspar and pyroxene, with the plutonic equivalent of basalt. It forms deep underground where mafic magma cools slowly enough for its mineral grains to grow large and interlock visibly. Its dense, speckled black-and-white texture makes it a popular dimension stone sold commercially as black granite.
Amphibolite vs Gabbro FAQ
Is Amphibolite the same as Gabbro?
No. Amphibolite is a metamorphic rock while Gabbro is a igneous rock. Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Amphibolite from Gabbro?
Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Luster is different: Amphibolite is dull while Gabbro is dull to vitreous (in crystals). Hold a thin edge to the light: Amphibolite is opaque, Gabbro is Opaque.
Which is harder, Amphibolite or Gabbro?
They are about equally hard, both near Mohs 5.5.
Which is more valuable, Amphibolite or Gabbro?
Typical specimens of Amphibolite and Gabbro trade in a similar range, around $10.
