Olivine Basalt (Pumice or Scoria)

Hardness of 5-6 on the Mohs scale, dark green to greyish-black color, dull luster, aphanitic texture with prominent vesicular holes (gas cavities), specific gravity around 2.7-3.0.

Formed from gas-rich mafic lava cooling rapidly on or near the Earth's surface, trapping gas bubbles which create the vesicular texture. Commonly found in volcanic regions worldwide.

Used in lightweight aggregate, landscaping, abrasives, and sometimes tumbled into decorative beach stones.

The distinctive greenish tint is often due to the weathering or presence of olivine crystals within the basaltic matrix. Vesicular basalts can sometimes float on water if they are very porous like pumice, though scoria is typically heavier and sinks.

Easily identified by its dark color, vesicular (holey) texture, and occurrence in volcanic areas or beaches near former volcanic activity.