igneous
Red Scoria
Scoria (Vesicular Basalt)
Hardness: 5-6 Mohs. Color: Reddish-brown to dark red (oxidized). Luster: Dull/Earthy. Structure: Highly vesicular (porous/bubbly), volcanic glass and crystals. Specific gravity: Low (often floats briefly/lightweight).
- Hardness
- 5-6 Mohs
- Color
- Reddish-brown to dark red (oxidized)
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish-brown to dark red (oxidized). Luster: Dull/Earthy. Structure: Highly vesicular (porous/bubbly), volcanic glass and crystals. Specific gravity: Low (often floats briefly/lightweight).
Formation & geological history
Formed during explosive volcanic eruptions when magma containing dissolved gases is ejected. The gases expand into bubbles (vesicles) as the pressure drops, which are then frozen into the cooling rock. Red color is due to the oxidation of iron within the basaltic lava.
Uses & applications
Landscaping, gas grill lava rocks, drainage, lightweight concrete aggregate, high-temperature insulation, and road traction in snowy conditions.
Geological facts
Scoria is often confused with pumice, but it is denser and has larger vesicles with thicker walls. The red color suggests it formed in an environment with high oxygen availability during the cooling process.
Field identification & locations
Identify by its rough, sharp texture and noticeable air holes (pores). It is relatively light for its size but heavier than most pumice. Found in volcanic regions like the American Southwest, Hawaii, and Iceland.
