The last active volcanoes in Germany became extinct 11,000 to 12,500 years ago in the Eifel area. The lava emitted during the gas-rich eruptions became frothed up by water vapor and carbon dioxide that built-up in large quantities in the upper layers.

Directly below the surface of these former volcanoes is an air-pore-rich gravel shaped mineral made from purely siliceous raw materials - the Naturally expanded silicate.

ROTEC^® extracts and refines this ecologically perfected raw material into innovative lightweight aggregates and ecologically valuable substrates.