Amygdaloidal texture  

The oval feature in this photomicrograph is an amygdule: a formerly open vesicle which has been filled with a secondary mineral(s) precipitated from low-T ground waters which have penetrated into the rock. In this case, the amygdule is probably filled with a zeolite mineral.

UNC sample

H-64

Rock type

amygdaloidal basalt

Locality

unknown