Comparison · Metamorphic Rocks
Amphibolite vs Hornfels
Amphibolite and Hornfels are easy to confuse because both are metamorphic rocks. 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 Hornfels
- Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Amphibolite leaves a variable; usually pale gray to white streak on unglazed porcelain, Hornfels leaves variable; usually pale gray.
- They overlap in black, green, gray, white, and red, but Hornfels also comes in brown.
Amphibolite vs Hornfels properties
| Property | Amphibolite | Hornfels |
|---|---|---|
| Type | Metamorphic Rocks | Metamorphic Rocks |
| Mohs hardness | 5.5 | 6 |
| Luster | dull | dull |
| Streak | Variable; usually pale gray to white | Variable; usually pale gray |
| Transparency | opaque | opaque |
| Specific gravity | 3 | 2.7 |
| Crystal system | varies | varies |
| Common colors | Black, Dark green, Gray, White, Red | Gray, Black, Brown, Green, Red, White |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Amphibolite and Hornfels 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 Hornfels
Hornfels is a hard, dense, fine-grained contact metamorphic rock. It often looks dark, tough, and baked, with little visible layering.
Amphibolite vs Hornfels FAQ
Is Amphibolite the same as Hornfels?
No. Both are metamorphic rocks, but they are distinct rock types with different hardness, streak or luster. 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 Hornfels?
Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Amphibolite leaves a variable; usually pale gray to white streak on unglazed porcelain, Hornfels leaves variable; usually pale gray. They overlap in black, green, gray, white, and red, but Hornfels also comes in brown.
Which is harder, Amphibolite or Hornfels?
Hornfels is harder: Mohs 6 against Mohs 5.5 for Amphibolite.
Which is more valuable, Amphibolite or Hornfels?
Typical specimens of Amphibolite and Hornfels trade in a similar range, around $10.
