Comparison · Igneous Rocks vs Metamorphic Rocks
Basalt vs Hornfels
Basalt and Hornfels are easy to confuse. Both sit near Mohs 6, 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 Basalt and Hornfels
- Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Basalt leaves a variable; test individual minerals streak on unglazed porcelain, Hornfels leaves variable; usually pale gray.
- They overlap in black, gray, and green, but Hornfels also comes in brown, red, and white.
Basalt vs Hornfels properties
| Property | Basalt | Hornfels |
|---|---|---|
| Type | Igneous Rocks | Metamorphic Rocks |
| Mohs hardness | 6 | 6 |
| Luster | dull | dull |
| Streak | Variable; test individual minerals | Variable; usually pale gray |
| Transparency | opaque | opaque |
| Specific gravity | 3 | 2.7 |
| Crystal system | varies | varies |
| Common colors | Black, Dark Gray, Dark Green | Gray, Black, Brown, Green, Red, White |
| Rarity | common | common |
| Typical specimen value | $1–$30+ | $1–$75+ |
Which is more valuable?
Hornfels is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Basalt, and premium Hornfels can reach $75 or more.
About Basalt
Basalt is a dark, fine-grained volcanic rock that makes up most of the ocean floor and Hawaiian Islands. It often forms distinctive columnar jointing.
About Hornfels
Hornfels is a hard, dense, fine-grained contact metamorphic rock. It often looks dark, tough, and baked, with little visible layering.
Basalt vs Hornfels FAQ
Is Basalt the same as Hornfels?
No. Basalt is a igneous rock while Hornfels is a metamorphic rock. Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Basalt from Hornfels?
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Basalt leaves a variable; test individual minerals streak on unglazed porcelain, Hornfels leaves variable; usually pale gray. They overlap in black, gray, and green, but Hornfels also comes in brown, red, and white.
Which is harder, Basalt or Hornfels?
They are about equally hard, both near Mohs 6.
Which is more valuable, Basalt or Hornfels?
Hornfels is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Basalt, and premium Hornfels can reach $75 or more.
