Libyan desert glass is a naturally occurring silica glass found scattered across an area of the Great Sand Sea in the Egyptian Western Desert, near the modern Egyptian-Libyan border. The material is unusual among natural glasses for its very high silica content, generally above 96 per cent SiO2, and for its pale yellow to greenish-yellow colour and high transparency. Pieces range from small fragments to specimens weighing several kilograms.

Origin

The current consensus, supported by laboratory evidence including the presence of high-pressure mineral phases such as reidite, places the formation of the glass at approximately 29 million years ago through an impact-related event. Whether the glass formed in a direct impact crater excavation or by an airburst-induced melting of surface sand has been debated; geochemical evidence is consistent with extraterrestrial contamination at low levels. The 2019 confirmation of reidite in Libyan desert glass effectively ruled out a non-impact origin in favour of an impact or airburst event.

The Tutankhamun connection

The most cited cultural reference for Libyan desert glass is the central scarab carving on a pectoral ornament recovered from the tomb of Tutankhamun. The carving was identified as Libyan desert glass in the 1990s, establishing that the material had been collected and worked by Egyptian craftsmen over three thousand years ago, well before any modern survey of the source area.

The trade today

The material is faceted and carved by lapidaries who appreciate its colour and natural curiosity value. It is hard enough at 6 to 6.5 on the Mohs scale for general jewellery use with sensible care, and refractive index measurements cluster around 1.46. Egyptian export controls on desert glass have tightened since the early 2000s, and pieces in trade circulation are most often older holdings from before those controls; this has supported a steady price level. There is no recognised synthetic counterpart in the gemstone market.