Libyan Desert Glass

The glass lies as centimetre- to decimetre-sized, strongly wind-eroded pieces on the floor of corridors between sand dunes in the southwestern Great Sand Sea of western Egypt, near the Libyan border. Melting nearly pure silica requires temperatures above 1,600 °C. Its origin has long been debated between a meteorite impact and the heat of a large airburst. Evidence for an impact includes lechatelierite, baddeleyite and zirconia formed from zircon, a meteoritic component in some samples, traces of former reidite in zircon (Cavosie and colleagues, 2019), shocked quartz in local bedrock (Koeberl and Ferrière, 2019) and a high-pressure zirconia phase (Kovaleva and colleagues, 2024). The source crater has not been found; it may have been almost completely eroded.

Libyan Desert Glass is distinguished from other natural glasses by its very high silica content (about 98%, compared with about 68–82% in most tektites), its low density of about 2.2 g/cm³ and its pale yellow colour. Inside, it can show bubbles, colour bands linked to differences in bubble content, schlieren, and inclusions such as cristobalite and partly digested minerals including lechatelierite and baddeleyite. Rough pieces are irregular, wind-polished lumps rather than the splash shapes typical of many tektites.

The carved yellow scarab at the centre of a pectoral (breastplate) from the tomb of Tutankhamun, now in the Egyptian Museum in Cairo, is made of Libyan Desert Glass; Italian researcher Vincenzo de Michele noticed the resemblance in 1996, and a simple optical measurement confirmed the match in 1998. British explorers first reached the glass field in the early 1930s, and the glass was scientifically described by P. A. Clayton and L. J. Spencer in 1934. The Tutankhamun link later prompted the documentary "Tutankhamun's Fireball".