Our lava rock is a unique product that weighs less than half of other landscaping aggregates. Less weight means more coverage per ton. You can expect to get almost three times more coverage with lava rock over other decorative rock. The reason lava rock is so much lighter is its natural porosity. Lava rock insulates the ground from heat and cold. Studies show that lava rock is more effective in retaining moisture and reducing evaporation of moisture in topsoil, than wood mulch products. It keeps moisture in the ground but will not rot, decay or be subject to color fade like other wood mulches. Lava rock is a permanent mulch replacement.