igneous
Vesicular Basalt (Scoria)
Basalt with vesicular texture
Hardness: 5-6 Mohs. Color: Dark gray to black. Luster: Dull/Earthy. Structure: Aphanitic (fine-grained) with high vesicularity (small holes/voids). Heavy but feels lighter than solid basalt due to air pockets.
- Hardness
- 5-6 Mohs
- Color
- Dark gray to black
- Luster
- Dull/Earthy
Identified More igneous →
Explore Vesicular Basalt (Scoria) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 Mohs. Color: Dark gray to black. Luster: Dull/Earthy. Structure: Aphanitic (fine-grained) with high vesicularity (small holes/voids). Heavy but feels lighter than solid basalt due to air pockets.
Formation & geological history
Formed from the rapid cooling of mafic lava rich in dissolved gases. As the lava erupts onto the surface, the drop in pressure causes gases to bubble out, which are then trapped as the lava solidifies into rock. Common in volcanic fields and shield volcanoes.
Uses & applications
Used in landscaping, high-temperature insulation (mineral wool), gas grill lava rocks, and construction aggregates. Highly porous varieties are used in drainage systems and biological filters.
Geological facts
The holes in this rock are called vesicles. When these holes are later filled by other minerals like quartz or calcite, the rock is called an amygdaloidal basalt. Basalt is the most common rock type in the Earth's crust and makes up the entirety of the ocean floor.
Field identification & locations
Identify by its dark color, fine-grained texture, and numerous small, sponge-like holes. Found in volcanic regions like Hawaii, Iceland, and the Pacific Northwest. Watch for its rough, abrasive surface which can be sharp.
