Small lava rock may be the perfect size material for your gas fire pit. These half and quarter-inch sized pieces provide a great coverage as a base material in addition to your fire pit products, such as 1/2-inch fire glass or even fire beads. A ten-pound bag of lava rock will fill as much area as twenty pounds of fire glass. You will discover that lava rock is an efficient and inexpensive fill material for your fire pit. 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. Because of it being a natural material, please remember your lava rock will differ in shades of brown to black. Includes 10 pounds of lava rocks.