Lava Rocks instantly transform your outdated fire pit into a timeless classic. Naturally occurring, these lava rocks are formed as volcanic magma rises to the surface, cools and releases gases which gives these rocks their coarse surface. Because they are volcanic, they can withstand extremely high temperatures without sustaining any damage or crumbling. Lava Rocks can be used on their own as a focal point of your fire pit, or as a base layer underneath fire glass to keep the costs of your fire pit project down. The choice is yours! Lava Rock can withstand high temperatures in any fire feature because of the natural process magma goes through when cooling. As the magma cools, the rocks release gas bubbles that form a coarse, rough surface around the rock. Size: medium. Material: Lava stone.