vesicular

The erythematous and vesicular varieties are the most favorable.

Vesicular: More or less covered with minute vesicles due to gas formation; more minute than bullate.

When it becomes vesicular, it passes gradually into the highly porous rock called pumice.

Occasionally we meet with igneous rocks which are more or less vesicular and amygdaloidal throughout their entire mass.

As a rule, those lavas which are of inferior specific gravity are much more vesicular than the denser and heavier varieties.