1. A PROCESS OF PRODUCING A LIGHT WEIGHT AGGREGATE WHICH COMPRISES FORMING A MIXTURE CONSISTING ESSENTIALLY OF PARTICLES OF WATER GRANULATED SLAG AND PARTICLES OF REFRACTORY MATERIAL HAVING A SOFTENING POINT OF ABOVE 2300* F., THE PARTICLES OF THE REFRACTORY MATERIAL HAVING A MESH SIZE BELOW APPROXIMATELY 20 MESH AND BEING PRESENT IN AMOUNT FROM APPROXIMATELY 20 PERCENT TO 60 PERCENT BY WEIGHT OF THE COMPOSITION, AND HEATING THE MIXTURE IN MOTION AT A TEMPERATURE AT WHICH THE SLAG BECOMES PLASTIC AND THE ENTRAPPED GASES FROM THE WATER GRANULATED SLAG BLOAT THE PARTICLES INTO GLOBULES