Libyan Desert Glass

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...
The Libyan desert glass has been dated as having formed about 26 million years ago, which made scientists assume that the glass here was formed when a meteorite struck earth around this time, but the absence of an impact crater pose problems for this theory...
Local inhabitants in the Neolithic period made tools out of the glass, and later the Egyptians used it as jewel. A large piece of carved stone on the breastplate of the famous Egyptian pharaoh Tutankhamun was identified as none other than Libyan Desert Glass.. More info and photos at Amusing Planet.