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The most mysterious material – Libyan desert glass
Text: Jaak Kikas, UT Institute of Physics
Photos: Jaak Kikas and Wikimedia
A piece of Libyan desert glass. Due to the high purity of the material light is strongly transmitted through it.
The year 1932. The desert survey expedition led by Patrick A. Claytoni discovers something extraordinary in western Egypt, in a desert bordering to Libya. In a rather limited area chunks of very pure (about 98 %) natural quartz glass were found; the largest weighed nearly twenty kilos. This finding-place has remained unique in the world. The area is an oval measuring 130 x 50 km (Google Maps). From tracks of the natural radioactive decay in the glass it has been established that the event – of whatever kind – that was the origin of the glass occurred 28 million years ago.
What can it have been? Natural quartz glass may have several origins. Firstly volcanic glass or obsidian. This however contains much additional matter which colours it nearly black. And no volcanoes – active or dormant – are known near the Libyan desert glass find area. Quite pure quartz glass may also be produced as a result of lightning hitting quartz sand. But such artefacts – fulgurites – have a characteristic, easily recognisable shape and are smaller than the large lumps of desert glass.
A small piece of moldavite.
One more possibility remains for the origin: meteoritic. Locations for finds of such naturally created quartz glass – tektite – are known from nearly all continents on the globe. The best known tektites in Europe are the moldavites which have been used for decorative purposes because of their beautiful greenish colour.
The origin of moldavite is thought to be the fall of a giant meteorite some 14,3 – 14,5 million years ago on to the territory of present-day Bavaria (the Nördlinger Ries circular depression). The molten sand that was thrown up when it collided with the ground fell down on the areas of today’s Bohemia and Moravia (Czech Republic) through which the Vltava (German Moldau) river flows. The problem with the Libyan desert glass is (was) however the fact that no meteoritic crater that could be tied to the formation of the glass had been identified in the surrounding area. Because of this the most divergent possibilities for the formation of the desert glass have been offered – starting with some low-temperature chemical (sol-gel) process, to a nuclear war between ancient civilisations (the reference above to the method for determining the age of the desert glass should not be read as confirmation of this view!) or to a collision between Earth and a celestial body with an extraordinary composition.
The Kebira crater. Is this the origin of the Libyan desert glass?
Lately however a formation has been identified in the area in question which has been tied to the genesis of the Libya desert glass. It is a partly visible ring structure with a diameter of 31 km which the discoverers - Farouk El-Baz and Eman Ghoneim from Boston University – named the Kebira crater (Google Maps). Incidentally Farouk El Baz served with NASA as selector of landing sites in the one-time Apollo Moon Mission projects. Whether there really is a meteoritic crater in Kebira and whether the origin of this also could be the origin of the Libyan desert glass – these are questions which cannot be answered without on-site investigations. Up to now the answers are still lacking.
The sacred scarab on Tutankhamun’s breast plate is carved from Libyan desert glass.
Why talk of the Libyan desert glass as a material, that is, a substance that is used for making something? When Howard Carter discovered the tomb of Egyptian pharaoh Tutankhamun, untouched by robbers, in 1922, there was among the innumerable treasures of the tomb also the breastplate of the Pharaoh where the image of Egypt’s sacred beetle – the scarab – was carved out of an unknown stone material. Only much later (1998) the Italian mineralogist Vincenzo de Michele established that this material was Libyan desert glass. But the use of this material goes much further back in history – evidence has been found that shows that the material was used by the local inhabitants in the Neolithic period and even earlier. Similar to obsidian the Libyan desert glass yields very sharp-edged shards on shattering and is exceptionally well suited for making different “stone” working or hunting tools and weapons.
Stone-Age high tech – knife made of obsidian.
Oh, no! we might protest – how can such a unique material be used for such everyday purposes? But how were the Stone Age inhabitants of this area to know that these things – which were just lying about in their “backyard” – were so extremely rare elsewhere in the world? Or the other way round – maybe we can learn something from this, and consider that certain things may turn out to be rarities in the future - although today they are everywhere.
See also Materjalimaailm: Libyan desert glass / Obsidian.
