A deep-colored alternative to harder stone, lava rock is so porous that it's lightweight, providing more coverage per ton. Use leftovers to line the bottom of a gas grill and distribute heat more evenly, or to filter water in areas.
1. Red flowerrock, from Lang Stone, $215 per ton (about 33 to 50 cu. ft.). 2. Lava rock, 3/8-in., from Palmer Coking Coal Co., $48 per ton (180-240 cubic feet).