Rock and slag insulations, sometimes referred to as mineral wool, have been produced naturally for centuries. During volcanic eruptions, when a strong wind passes over a stream of molten lava, the lava is blown into fine silky threads that look like wool. From this natural inspiration sprang one of the most innovative and versatile insulation products on the market today. Today’s rock and slag wool insulations are high-tech versions of their predecessors, produced from plentiful basalt and industrial slag.