Between the borders of Egypt and Libya is the Great Sand Sea, an enormous sandy desert that stretches about 650 km from north to south and 300 km from east to west, covering an area the size of Ireland. Prevailing winds have organized this great sand mass into huge longitudinal crested dunes rising 100 meters high at places and stretching uninterrupted for hundreds of kilometers, separated by flat corridors about a kilometer or two wide. In these long narrow gaps are areas where the underlying bedrock is exposed. In these exposed surfaces a curious natural glass is found.
The so called Libyan Desert Glass is the purest natural silica glass ever found on earth. The glass is generally yellow in color. It can be very clear or it can be a milky, and even contain tiny bubbles, white wisps, and inky black swirls. Over a thousand tons of these glass are strewn across hundreds of kilometers of bleak desert. Most of these are the size of pebbles polished smooth by the abrasive action of the blowing sand. Others are chunks of considerable size and weight. The biggest piece ever found weighed around 26 kg.