igneous
Scoria
Vesicular Basalt / Scoriaceous Basalt
Hardness: 5-6 (Mohs scale); Color: Black, dark gray, or reddish-brown; Luster: Dull/Sub-metallic; Crystal Structure: Aphanitic (fine-grained matrix); Cleavage: None; Specific Gravity: 1.0 - 2.0 (porous and lightweight).
- Hardness
- 5-6 (Mohs scale)
- Color
- Black, dark gray, or reddish-brown
- Luster
- Dull/Sub-metallic
Identified More igneous →
Explore Scoria in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs scale); Color: Black, dark gray, or reddish-brown; Luster: Dull/Sub-metallic; Crystal Structure: Aphanitic (fine-grained matrix); Cleavage: None; Specific Gravity: 1.0 - 2.0 (porous and lightweight).
Formation & geological history
Formed from extrusive volcanic eruptions where magma containing trapped gases is expelled into the air or flows on the surface. Rapid cooling and gas expansion create the vesicular (pitted) texture. Found in volcanic regions like Hawaii, Iceland, and the Andes.
Uses & applications
Commonly used in landscaping (lava rocks), high-temperature insulation, lightweight concrete aggregate, drainage systems, and as an abrasive in 'stone-washed' jeans.
Geological facts
Scoria is often mistaken for pumice, but scoria is more dense and darker in color. Unlike some pumice, scoria is usually too heavy to float in water because of its basaltic composition and larger vesicle walls.
Field identification & locations
Identify by its 'Swiss cheese' appearance, dark color, and rough, sharp edges. Commonly found on the slopes of cinder cone volcanoes. Collectors look for pieces with iridescent coatings or large, unbroken air pockets.
