A method of manufacturing a building material includes the steps of directing molten volcanic magma from an underwater volcanic magna vent to a level above seal level via a tube formed from the magma, directing the molten volcanic magma into a mold located on a floating barge or located on land, and cooling the magma in the mold to form a building material. As an alternative to obtaining the magma from an underwater vent, the molten volcanic magma can be obtained from a vent on land, a lava pool or stream, tapping a lava tube, or the like. The molten volcanic magma can be cast, molded, formed, extruded, flossed, stranded, foamed and used as a heat source to produce harbor works, floors, walls, roofs, pipe, flotation, barges, vessels, insulation, fiber reinforcing and electricity.