igneous
Scoria
Scoria (Vesicular Basaltic Rock)
Hardness: 5-6 (Mohs). Color: Dark brown, black, or reddish-brown. Luster: Dull. Texture: Highly vesicular (pitted with holes). Crystal structure: Aphanitic (fine-grained). Specific gravity: Low (often floats briefly)
- Hardness
- 5-6 (Mohs)
- Color
- Dark brown, black, or reddish-brown
- Luster
- Dull
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Physical properties
Hardness: 5-6 (Mohs). Color: Dark brown, black, or reddish-brown. Luster: Dull. Texture: Highly vesicular (pitted with holes). Crystal structure: Aphanitic (fine-grained). Specific gravity: Low (often floats briefly)
Formation & geological history
Formed from the rapid cooling of gas-rich basaltic lava. The numerous holes (vesicles) are created by gas bubbles trapped in the molten material during solidification. It is of volcanic origin, generally from the Holocene or Pleistocene epochs in many active volcanic regions.
Uses & applications
Used extensively in landscaping, gas grill lava rocks, lightweight concrete aggregate, high-temperature insulation, and as a drainage material in horticulture.
Geological facts
Unlike pumice, scoria has larger vesicles and thicker cell walls, causing it to sink in water once submerged. It is often what people are referring to when they say 'lava rock' for their outdoor fire pits.
Field identification & locations
Identify by its lightweight feel, dark color, and sponge-like appearance with many visible holes. It is commonly found near volcanic cones like cinder cones. Small fragments are often used in commercial gravel.
