Scoria
Image: “Jonathan Zander (<a href="//commons.wikimedia.org/wiki/User:Digon3" title="User:Digon3">Digon3</a>)" (CC BY-SA 3.0)
Mineral NameScoria
Chemical FormulaVariable, typically basaltic or andesitic composition (mafic volcanic rock)
Mohs HardnessVariable, generally 5-7 (for constituent minerals)
Streak ColorGrey to brownish-black
CleavageNone (rock, not a single mineral)
FractureUneven to irregular (due to vesicles)
Specific Gravity1.0-2.0 (variable due to porosity, can float)
Colorsdark grey, black, reddish-brown
TransparencyOpaque
Type LocalityWorldwide in volcanic regions (e.g., Hawaii, Canary Islands, Italy)
Mineral GroupIgneous rock (extrusive volcanic rock)
Useslandscaping, construction aggregate, BBQ briquettes, lightweight concrete
Associated Mineralsolivine, pyroxene, plagioclase
Raritycommon
Description
A dark, highly vesicular volcanic rock, typically reddish-brown to black, characterized by numerous gas bubbles (vesicles) that give it a spongy appearance.
Geological Context
Scoria forms during explosive volcanic eruptions when gas-rich magma is ejected into the air and cools rapidly, trapping gas bubbles within the solidifying rock.
