RocksdayVolcanic Bomb
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.
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.
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.
Often confused with
Where it's found
- Hawaii
- Iceland
- Auvergne, France
- Arizona
Uses
Teaching specimens.
Rock tumbling
Can be tumbled with care.
Did you know?
Breadcrust bombs crack because the outside chills into a skin while the inside is still expanding.
Volcanic Bomb FAQ
What is volcanic bomb?
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. 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.
How do you 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.
How hard is volcanic bomb?
Volcanic Bomb has a Mohs hardness of about 5–6. Its hardness varies from 5 to 6, so scratch tests depend on the piece.
Where is volcanic bomb found?
Notable localities include Hawaii; Iceland; Auvergne, France; and Arizona.
What is volcanic bomb used for?
Teaching specimens.
Can you tumble volcanic bomb?
Yes, with care.
What is volcanic bomb often confused with?
Volcanic Bomb is most often confused with Scoria, Pumice and Concretion. Scoria is bubbly cinder without a streamlined or breadcrust shape. Pumice is pale and light enough to float. Concretions grew in sediment and are not volcanic glass or lava.
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