Comparison · Igneous Rocks
Andesite vs Scoria
Andesite 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 Andesite and Scoria
- Both sit near Mohs 5–6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Andesite feels noticeably heavier for its size (specific gravity 2.5–2.8 versus 1.5–2.6 for Scoria).
- They overlap in brown and black, but Andesite also comes in gray and green and Scoria also comes in red.
Andesite vs Scoria properties
| Property | Andesite | Scoria |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 5–6 | 5–6 |
| Luster | Dull groundmass with vitreous phenocrysts | Dull, glassy |
| Transparency | Opaque | Opaque |
| Specific gravity | 2.5–2.8 | 1.5–2.6 |
| Common colors | Gray, Dark gray, Greenish gray, Brown, Black | Dark red, Black, Brown, Reddish brown |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Andesite and Scoria trade in a similar range, around $10.
About Andesite
Andesite is a fine-grained, intermediate volcanic rock formed from lava with a silica content between basalt and rhyolite, typically 57 to 63 percent. It is named for the Andes Mountains, where it makes up much of the volcanic arc, and its groundmass is usually too fine to identify individual minerals without magnification. Andesite forms at convergent plate boundaries where oceanic crust melts beneath continental or island arcs.
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.
Andesite vs Scoria FAQ
Is Andesite 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 Andesite from Scoria?
Both sit near Mohs 5–6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Andesite feels noticeably heavier for its size (specific gravity 2.5–2.8 versus 1.5–2.6 for Scoria). They overlap in brown and black, but Andesite also comes in gray and green and Scoria also comes in red.
Which is harder, Andesite or Scoria?
They are about equally hard, both near Mohs 5–6.
Which is more valuable, Andesite or Scoria?
Typical specimens of Andesite and Scoria trade in a similar range, around $10.
