Any amazing gas fire feature begins with a proper and solid base. You can use fire glass or fire stones in your fireplace alone, but for deep set fire pits it is best to lay down a lava rock base. Not only is it lighter weight by mass (a ten-pound bag of lava rock will fill as much area as twenty pounds of fire glass) but is more cost effective for your fire pit project. 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.