Comparison · Igneous Rocks
Pumice vs Scoria
Pumice and Scoria are easy to confuse because both are igneous rocks. Both sit near Mohs 5–6, 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 Pumice and Scoria
- Both sit near Mohs 5–6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Scoria feels noticeably heavier for its size (specific gravity 1.5–2.6 versus 0.25–0.9 for Pumice).
- Hold a thin edge to the light: Pumice is Opaque, translucent in thin shards, Scoria is Opaque.
- They overlap in brown, but Pumice also comes in white, gray, and yellow and Scoria also comes in red and black.
Pumice vs Scoria properties
| Property | Pumice | Scoria |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 5–6 | 5–6 |
| Luster | Dull to glassy | Dull, glassy |
| Transparency | Opaque, translucent in thin shards | Opaque |
| Specific gravity | 0.25–0.9 | 1.5–2.6 |
| Crystal system | Amorphous | — |
| Common colors | White, Light gray, Tan, Pale yellow | Dark red, Black, Brown, Reddish brown |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Pumice and Scoria trade in a similar range, around $10.
About Pumice
Pumice is a light-colored, extrusive volcanic rock so full of trapped gas bubbles, or vesicles, that it can float on water. It forms when gas-rich, silica-rich magma is violently depressurized during an explosive eruption, freezing the expanding bubbles in place as volcanic glass. Its extremely low density and rough, abrasive texture have made it useful to people for thousands of years.
About Scoria
Scoria is a dark, highly vesicular volcanic rock of basaltic to andesitic composition, riddled with gas bubbles trapped as the lava cooled and depressurized rapidly. It is denser and darker than pumice, containing thicker vesicle walls and less silica, which is why scoria typically sinks in water while pumice floats. Its red color, when present, comes from oxidized iron in the rock.
Pumice vs Scoria FAQ
Is Pumice the same as Scoria?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 5–6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Pumice from Scoria?
Both sit near Mohs 5–6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Scoria feels noticeably heavier for its size (specific gravity 1.5–2.6 versus 0.25–0.9 for Pumice). Hold a thin edge to the light: Pumice is Opaque, translucent in thin shards, Scoria is Opaque.
Which is harder, Pumice or Scoria?
They are about equally hard, both near Mohs 5–6.
Which is more valuable, Pumice or Scoria?
Typical specimens of Pumice and Scoria trade in a similar range, around $10.
