igneous
Lava Rock (Scoria)
Scoria (Mafic volcanic rock)
Hardness: 5-6 Mohs (can vary due to porosity); Color: Dark brown, black, or reddish-brown; Luster: Dull, earthy; Crystal structure: Aphanitic (fine-grained) with a highly vesicular (holed) texture; Specific Gravity: Low (often floats briefly before saturation).
- Hardness
- 5-6 Mohs (can vary due to porosity)
- Color
- Dark brown, black, or reddish-brown
- Luster
- Dull, earthy
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Physical properties
Hardness: 5-6 Mohs (can vary due to porosity); Color: Dark brown, black, or reddish-brown; Luster: Dull, earthy; Crystal structure: Aphanitic (fine-grained) with a highly vesicular (holed) texture; Specific Gravity: Low (often floats briefly before saturation).
Formation & geological history
Formed from the rapid cooling of mafic lava (high in iron and magnesium) that is rich in dissolved gases. The gas bubbles are trapped as the lava solidifies, creating the characteristic holes (vesicles). Found in volcanic regions worldwide.
Uses & applications
Commonly used in landscaping (lava rock), as a high-temperature insulation material, in gas grills for heat distribution, in road construction, and for drainage in horticulture.
Geological facts
Scoria is different from pumice because it is denser and has larger vesicles; while pumice is felsic (light-colored and silica-rich), scoria is mafic (dark-colored). The holes are called vesicles and represent trapped gas bubbles from the volcanic eruption.
Field identification & locations
Identify by its light weight relative to its size and its swiss-cheese-like appearance. It is commonly found near volcanic vents or in cinder cones. Collectors look for unique shapes or specific color variations.
