RocksdayScoria vs Volcanic Bomb
The quickest way to tell Scoria from Volcanic Bomb: Volcanic Bomb feels noticeably heavier for its size (specific gravity 2.2–3 vs 1–2).
Dark, bubble-filled lava that piles up as cinder cones. Larger holes and heavier than pumice.
Photo: ScoriaPumice, CC0
A lump of lava larger than 64 mm that was still molten when it was thrown out, so it froze in a streamlined or cracked shape.
Photo: National Park Service/Ed Shiinoki, Public domain
Quick tests
- Heft: Volcanic Bomb feels noticeably heavier for its size (specific gravity 2.2–3 vs 1–2).
Key differences
- Scoria is bubbly cinder without a streamlined or breadcrust shape.
Side by side
| Property | Scoria | Volcanic Bomb |
|---|---|---|
| Type | Igneous rock | Igneous rock |
| Mohs hardness | 5.5–6 | 5–6 |
| Luster | Dull | Dull to glassy |
| Colors | Black, Red, Brown | Black, Brown, Red, Gray |
| Crystal system / structure | Vesicular (bubbly) | Aerodynamic pyroclast |
| Specific gravity | 1–2 | 2.2–3 |
| Found in | Sunset Crater, Arizona; Mauna Kea, Hawaii | Hawaii; Iceland |
Properties that are the same for both are grayed out.
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 →How to identify volcanic bomb
- Almond, spindle or ribbon shape, or a round lump with a cracked crust.
- Often a dense core and a bubbly or breadcrust outside.
- Basaltic ones are black to reddish brown.
Structure: Aerodynamic pyroclast
Full Volcanic Bomb guide →More comparisons
Frequently asked questions
What is the difference between scoria and volcanic bomb?
Scoria is an igneous rock with a Mohs hardness of about 5.5–6 and a dull luster, usually black, red or brown. Volcanic Bomb is an igneous rock with a Mohs hardness of about 5–6 and a dull to glassy luster, usually black, brown, red or gray.
How can you tell scoria from volcanic bomb?
Volcanic Bomb feels noticeably heavier for its size (specific gravity 2.2–3 vs 1–2). Scoria is bubbly cinder without a streamlined or breadcrust shape.
Could you tell them apart from a blurry close-up?
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