View source for Chemistry:Libyan desert glass

{{short description|Desert glass found in Libya and Egypt}}
[[Image:Libyan Desert Glass.jpg|thumb|right|Libyan desert glass]]
'''Libyan desert glass''' or '''Great Sand Sea glass''' is an [[Earth:Impactite|impactite]], made mostly of [[Chemistry:Lechatelierite|lechatelierite]],<ref name="Mindat">{{cite web | url=https://www.mindat.org/min-39796.html | title=Libyan Desert Glass | publisher=mindat.org | access-date=12 July 2020}}</ref> found in areas in the eastern Sahara, in the deserts of eastern Libya and western Egypt. Fragments of desert glass can be found over areas of tens of square kilometers.

== Geologic origin ==
[[File:GJ34-503-Seite3.gif|thumb|Partial distribution of Silica-glass in the Libyan Desert.  1934 map.]]
The origin of desert glass is uncertain. Meteoritic origins have long been considered possible, and recent research links the [[Chemistry:Glass|glass]] to impact features, such as [[Chemistry:Zircon|zircon]] breakdown, vaporized [[Chemistry:Quartz|quartz]] and meteoritic metals, and to an [[Astronomy:Impact crater|impact crater]].<ref>{{cite web|url=http://www.wits.ac.za/newsroom/newsitems/201310/21649/news_item_21649.html |title=First ever evidence of a comet striking Earth |publisher=Wits University |author1=Jan Kramers |author2=David Block |author3=Marco Andreoli |year=2013 |url-status=dead |archive-url=https://web.archive.org/web/20131010235550/http://www.wits.ac.za/newsroom/newsitems/201310/21649/news_item_21649.html |archive-date=2013-10-10 }}</ref><ref>Kramers, J.D et al (2013): Unique chemistry of a diamond-bearing pebble from the Libyan Desert Glass strewnfield, SW Egypt: Evidence for a shocked comet fragment. Earth and Planetary Science Letters 382, 21-31 {{doi|10.1016/j.epsl.2013.09.003}}</ref><ref>B. Kleinmann (1968): The breakdown of zircon observed in the Libyan desert glass as evidence of its impact origin. Earth and Planetary Science Letters 5, 497-501. {{doi|10.1016/S0012-821X(68)80085-8}}</ref><ref>Weeks, R. (1984): Libyan Desert glass: A review. Journal of Non-Crystalline Solids, 67, 593-619. {{doi|10.1016/0022-3093(84)90177-7}}</ref><ref>Seebaugh, W. R. & Strauss, A. M. (1984): Libyan Desert Glass: Remnants of an Impact Melt Sheet. LUNAR AND PLANETARY SCIENCE XV, 744-745. [Abstract.] {{bibcode|1984LPI....15..744S}}</ref><ref>Barbara Kleinmann, Peter Horn and Falko Langenhorst (2001): Evidence for shock metamorphism in sandstones from the Libyan Desert Glass strewn field. Meteoritics & Planetary Science 36, 1277-1282 {{doi|10.1111/j.1945-5100.2001.tb01960.x}}</ref><ref>Giovanni Pratesi, Cecilia Viti, Curzio Cipriani and Marcello Mellini (2002): Silicate-silicate liquid immiscibility and graphite ribbons in Libyan desert glass. Geochimica et Cosmochimica Acta 66, 903-911.{{doi|10.1016/S0016-7037(01)00820-1}}</ref> Some geologists<ref>{{Cite journal | doi=10.1111/j.1945-5100.2010.01283.x|title = Brownish inclusions and dark streaks in Libyan Desert Glass: Evidence for high-temperature melting of the target rock| journal=Meteoritics & Planetary Science| volume=45| issue=6| pages=973–989|year = 2010|last1 = Greshake|first1 = Ansgar| last2=Koeberl| first2=Christian| last3=Fritz| first3=Jörg| last4=Reimold| first4=W. Uwe| s2cid=128920720 }}</ref> associate the glass with [[Physics:Thermal radiation|radiative melting]] from meteoric large aerial bursts, making it analogous to [[Physics:Trinitite|trinitite]] created from sand exposed to the [[Physics:Thermal radiation|thermal radiation]] of a [[Physics:Effects of nuclear explosions|nuclear explosion]]. Libyan Desert glass has been dated as having formed about 29 million years ago.<ref name="Cavoisie">{{cite journal |last1=Cavosie |first1=Aaron J. |last2=Koeberl |first2=Christian |title=Overestimation of threat from 100 Mt–class airbursts? High-pressure evidence from zircon in Libyan Desert Glass |journal=Geology |date=1 July 2019 |volume=47 |issue=7 |pages=609–612 |doi=10.1130/G45974.1|bibcode=2019Geo....47..609C |s2cid=155125330 }}</ref> Like [[Chemistry:Obsidian|obsidian]], it was [[Chemistry:Knapping|knapped]] and used to make tools during the [[Earth:Pleistocene|Pleistocene]].<ref>{{cite web|url=http://archive.aramcoworld.com/issue/197905/desert.glass-an.enigma.htm|title=Desert Glass: An Enigma|website=Saudi Aramco World}}</ref>

The glass is nearly pure silica which requires temperatures above 1,600 °C to form – hotter than any igneous rock on Earth. However, few mineral relics survived from whatever caused the melting, including a form of quartz called [[Chemistry:Cristobalite|cristobalite]], a rarely occurring high-temperature mineral; and grains of the mineral [[Chemistry:Zircon|zircon]], although most have reacted to form a higher-temperature mineral called zirconia. Ideas about how the glass formed include melting during meteorite impact, or melting caused by an airburst from an asteroid or other object burning up high in Earth's atmosphere.<ref>{{Cite web|title=Libyan desert glass mystery solved|url=https://cosmosmagazine.com/history/archaeology/mystery-of-libyan-desert-glass-solved-at-last/|access-date=2021-10-21|website=cosmosmagazine.com|date=23 May 2019 |language=en-AU}}</ref>

==See also==

* {{annotated link|Chemistry:Atacama desert glass}}
* {{annotated link|Chemistry:Darwin glass}}
* {{annotated link|Astronomy:Hypatia (stone)}}
* {{annotated link|Earth:Kebira Crater}}
* {{annotated link|Chemistry:Tektite}}
* {{annotated link|Physics:Tunguska event}}

== References ==
[[File:Tutankhamun pendant with Wadjet.jpg|thumb|Tutankhamun's pectoral features a scarab carved from desert glass.<ref name="BBC">[http://news.bbc.co.uk/2/hi/science/nature/5196362.stm Tut's gem hints at space impact], BBC News, July 19, 2006.</ref>]]<references/>

== Literature ==
* V. de Michele (ed.): ''Proceedings of the Silica '96 Meeting on Libyan Desert Glass and related desert events'', Bologna, 1997 [https://web.archive.org/web/20090205004521/http://www.df.unibo.it/ricerca/proceed.htm Contents]
* P.A. Clayton / L.J. Spencer: ''Silica Glass from the Libyan Desert'', Vortrag vom 09.11.1933 [http://www.tlc-exped.net/Clayton-GJ1934-Seite1.html online]

== External links ==
*[https://scholar.google.com/scholar?q=%22desert+glass%22 Google Scholar: "Desert Glass"]
*[http://www.cmog.org/article/glass-nature Glass in Nature from The Corning Museum of Glass]

[[Category:Impact event minerals]]

{{Sourceattribution|Libyan desert glass}}