igneous
Scoria
Vesicular Mafic Extrusive Igneous Rock
Hardness: 5-6 on the Mohs scale; Color: Dark brown, black, reddish-brown; Luster: Dull; Crystal structure: Aphanitic (fine-grained) with abundant vesicles (air bubbles); Cleavage: None; Specific gravity: Varies, often floats briefly in water due to high porosity.
- Hardness
- 5-6 on the Mohs scale
- Color
- Dark brown, black, reddish-brown
- Luster
- Dull
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Physical properties
Hardness: 5-6 on the Mohs scale; Color: Dark brown, black, reddish-brown; Luster: Dull; Crystal structure: Aphanitic (fine-grained) with abundant vesicles (air bubbles); Cleavage: None; Specific gravity: Varies, often floats briefly in water due to high porosity.
Formation & geological history
Formed from gas-rich mafic or intermediate lava (such as basalt) that rapidly cools, trapping escaping gas bubbles as vesicles within the solidifying rock.
Uses & applications
Used in landscaping, lightweight aggregate in concrete, gas barbecue grills, and as an abrasive in foot care products.
Geological facts
Because of its high porosity and low density, some pieces of scoria are light enough to float on water until they become waterlogged.
Field identification & locations
Easily identified by its dark color and numerous small, rounded holes (vesicles). Commonly found near volcanic cones and basaltic lava flows worldwide.
