igneous
Vesicular Basalt (or Scoria)
Vesicular Basalt
Hardness: 5-6 (Mohs), Color: Grey to dark grey with reddish-brown oxidation in pores, Luster: Dull/Earthy, Crystal structure: Aphanitic (fine-grained), Cleavage: None, Specific Gravity: 2.8-3.0
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs), Color: Grey to dark grey with reddish-brown oxidation in pores, Luster: Dull/Earthy, Crystal structure: Aphanitic (fine-grained), Cleavage: None, Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava. The holes (vesicles) are created by gas bubbles trapped in the cooling magma as it reaches the surface. This specimen appears to be water-worn on a beach.
Uses & applications
Used in landscaping, road construction, as an abrasive (lava rock), and for heat retention in grills or saunas.
Geological facts
The vesicles in these rocks can sometimes fill with secondary minerals like quartz or calcite over millions of years, forming amygdaloidal basalt (and eventually geodes).
Field identification & locations
Look for a lightweight, 'holey' texture similar to a sponge but made of hard stone. Commonly found near volcanic sites or in glacial drift and riverbeds far from their origin.
