RocksdayBasalt vs Scoria
How to tell them apart
The most common volcanic rock on Earth. Dark, fine-grained lava that forms the ocean floor and vast lava plains.
Photo: James St. John, CC BY 2.0
Dark, bubble-filled lava that piles up as cinder cones. Larger holes and heavier than pumice.
Photo: ScoriaPumice, CC0
Quick tests
- Heft: Basalt feels noticeably heavier for its size (specific gravity 2.9–3.1 vs 1–2).
Key differences
- Scoria is mostly holes and much lighter.
- Basalt is mostly solid with only some holes.
Side by side
| Property | Basalt | Scoria |
|---|---|---|
| Type | Igneous rock | Igneous rock |
| Mohs hardness | 6 | 5.5–6 |
| Luster | Dull | Dull |
| Colors | Black, Gray | Black, Red, Brown |
| Crystal system / structure | Fine-grained (aphanitic) | Vesicular (bubbly) |
| Specific gravity | 2.9–3.1 | 1–2 |
| Found in | Hawaii; Iceland | Sunset Crater, Arizona; Mauna Kea, Hawaii |
Properties that are the same for both are grayed out.
How to identify basalt
- Dark gray to black and heavy.
- Grains too small to see.
- Often has gas bubbles (vesicles).
- May show six-sided columns in outcrops.
Structure: Fine-grained (aphanitic)
Full Basalt guide →How to identify scoria
- Black to rusty red.
- Full of large, rounded holes.
- Light for its size but sinks in water.
- Rough, crunchy texture.
Structure: Vesicular (bubbly)
Full Scoria guide →More comparisons
Could you tell them apart from a blurry close-up?
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