Rock Topics

Texture (Part 2)

• Other textural terms are used to describe igneous rocks.

Porphyritic rocks contain mineral crystals of various sizes.  Some grains are distinctly larger than others.

PorphyryPorphyritic Texture (Photograph by Stan Johnson)

Porphyritic rocks, like this one, have mineral grains of very different sizes. 

Vesicular texture refers to volcanic rocks that contain holes called vesicles that were formed by gas bubbles in lava.

ScoriaScoria with vesicular texture (Photograph by Parvinder Sethi)

This igneous rock is called scoria.  It has vesicular texture.  The vesicles form from escaping gas bubbles in cooling lava.