Desert Glass / Lechatelierite / Libyanite Info

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General and History

Tutankhamun Pendant *
Lechatelierite (also called Libyan Desert Glass, Libyanite or simply LDG) is an amorphous silica glass. It is no true mineral because it has no crystal structure although its formula (SiO2) is the same as quartz.

Stone Age Blade *
Since ancient times nomads collected lechatelierite in the Sahara desert in Africa. Because of its rarity lechatelierite was even mounted (as a cutted scarabaeus) in the famous pendant of Tutankhamun (1341 BC 1323 BC). The Italian mineralogist Vincenzo de Michele found out (in 1998) that this scarabaeus consists of lechatelierite instead of (formerly assumed) chalcedony.
Lechatelierite was even used as tools since prehistoric times (middle paleolithic, neolithic), recognizable on the chipped edges of such tools, e.g. arrowheads and blades. Some thousand years ago, the Libyan desert was a savannah with a lot of different huntable animals!


1934 Expedition *
On 29 December 1932, lechatelierite was newly discovered by Patrick Andrew Clayton during an Egyptian survey expedition * which made the first successfull east - west crossing of the "Great Sand Sea".
In December 1934, P.A. Clayton organized a special expedition to the lechatelierite area * at the Egyptian part of the Libyan desert, at 2530'E 2530'N, north of the Gilf Kebir plateau. He was joined by L.J. Spencer (Keeper of Minerals at the British Museum) and other mineralogists. They discovered that lechatelierite was spread over an area of appr. 6,500 km2.

* Photo: © www.egyptarchive.co.uk, Jon Bodsworth.
* Photo: © www.topgeo.de, Dr. Petr Zajicek.
* Photos: © www.fjexpeditions.com, Fliegel Jezerniczky Expeditions. Original source: Peter Clayton: "Desert Explorer" (1998)

Fulgurite *
Trinitite *
Lechatelierite was probably formed by the impact of a meteorite (appr. 28 - 30 million years ago) near the Gilf Kebir plateau in southwest Egypt, similar to the formation of moldavite in Europe.
It may be the result of high pressure shock metamorphism of the quartz sand during the impact, having ejected melted, glassy material called tektites, composed of almost pure SiO2. The "fission track" dating method [Storzer & Wagner (1977)] shows an age of appr. 29 million years.
Lechatelierite can also be formed by the high temperature melting of quartz sand grains during a lightning strike, resulting in a tube of melted sand, silica glass. This is called fulgurite.

Last but not least lechatelierite can develop from nuclear bomb explosions over a sandy ground: The artificial material "trinitite" was "produced" in course of the first nuclear bomb test explosion at "Trinity Flats" in New Mexico on 16 July 1945.

* Photo: © António Manuel Ináçio Martins.
* Photo: © www.uraniumminerals.com, Paul Schumacher.

Resources

Today we know that lechatelierite is concentrated in two areas of the Libyan desert: an oval-shaped (130 x 50 km, major axis: NNW - SSE) and a circular one (appr. 50 km in diameter). Probably two meteorites in tandem hit the earth.
Lechatelierite can be found in sand-free corridors between the dunes. It lies on the surface or is partly embedded. All lechatelierites have been pitted or smoothed by sand-blast.

Color and Transparency

Lechatelierite is transparent to translucent. It occurs in different colors: colorless, white, grey, light green or yellowish. It can contain bubbles, light or dark brown beads or small cristobalite crystals.
The size of the found lechatelierite varies from less than 50 g to more than 25 kg.

More informations: © www.cs.sandia.gov, Mark Boslough.