Comparison · Metamorphic Rocks
Amphibolite vs Slate
Amphibolite and Slate are easy to confuse because both are metamorphic rocks. Amphibolite is harder (Mohs 5.5) than Slate (Mohs 3.5), so Amphibolite will scratch Slate and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Amphibolite and Slate
- Amphibolite is harder (Mohs 5.5) than Slate (Mohs 3.5), so Amphibolite will scratch Slate and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
- Streak color differs: Amphibolite leaves a variable; usually pale gray to white streak on unglazed porcelain, Slate leaves variable; test individual minerals.
- They overlap in black, green, gray, and red, but Amphibolite also comes in white and Slate also comes in purple.
Amphibolite vs Slate properties
| Property | Amphibolite | Slate |
|---|---|---|
| Type | Metamorphic Rocks | Metamorphic Rocks |
| Mohs hardness | 5.5 | 3.5 |
| Luster | dull | dull |
| Streak | Variable; usually pale gray to white | Variable; test individual minerals |
| Transparency | opaque | opaque |
| Specific gravity | 3 | 2.8 |
| Crystal system | varies | varies |
| Common colors | Black, Dark green, Gray, White, Red | Gray, Black, Green, Purple, Red |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$100+ |
Which is more valuable?
Typical specimens of Amphibolite and Slate 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 Slate
Slate is a fine-grained metamorphic rock that splits easily into flat sheets. Its durability and water resistance make it ideal for roofing and flooring.
Amphibolite vs Slate FAQ
Is Amphibolite the same as Slate?
No. Both are metamorphic rocks, but they are distinct rock types with different hardness, streak or luster. Amphibolite is harder (Mohs 5.5) than Slate (Mohs 3.5), so Amphibolite will scratch Slate and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
How can you tell Amphibolite from Slate?
Amphibolite is harder (Mohs 5.5) than Slate (Mohs 3.5), so Amphibolite will scratch Slate and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Streak color differs: Amphibolite leaves a variable; usually pale gray to white streak on unglazed porcelain, Slate leaves variable; test individual minerals. They overlap in black, green, gray, and red, but Amphibolite also comes in white and Slate also comes in purple.
Which is harder, Amphibolite or Slate?
Amphibolite is harder: Mohs 5.5 against Mohs 3.5 for Slate.
Which is more valuable, Amphibolite or Slate?
Typical specimens of Amphibolite and Slate trade in a similar range, around $10.
