American Fire Glass LAVA-S-10 1/8"-1/2" Small Black Lava Rock 10 lbs. 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. Lava rock is also economical, you will see it is the best choice as the base filler for your fire feature to camouflage gas piping and tubes. If ceramic logs are your style choice of gas fireplace accessory, consider adding some of the lava rock around the area to create a very rustic and outdoorsy feel. Because of it being a natural material, please remember your lava rock will differ in shades of brown to black. Of course, lava rock is a beautiful and unique natural mineral, and will stand alone with any home or outdoor décor. American Fire Glass sifts, sorts and packs all of our lava rock by hand. This way we can guarantee that they are top quality, can be used in a firepit and have no left-over gas pockets that could burst.