Lechatelierite
Encyclopedia
Lechatelierite is silica glass, amorphous SiO2. One common way in which lechatelierite forms naturally is by very high temperature melting of quartz
sand during a lightning
strike. The result is an irregular, branching, often foamy hollow tube of silica glass called a fulgurite
.
Lechatelierite also forms as the result of high pressure shock metamorphism
during meteorite
impact cratering
and is a common component of a type of glassy ejecta
called tektite
s. Most tektites are blobs of impure glassy material, but tektites from the Sahara Desert
in Libya
and Egypt
, known as Libyan desert glass
, are composed of almost pure silica, that is almost pure lechatelierite. High pressure experiments have shown that shock pressures of 85 GPa
are needed to produce lechatelierite in quartz grains embedded in granite
.
Lechatelierite was formed during the impact of a meteorite
into a layer of Coconino Sandstone
at Meteor Crater
in Arizona
. It was puffed up to more than twice its size by steam and can now float on water.
Lechatelierite may also form artificially, a unique example being the trinitite
produced by melting of quartz sand at the first nuclear bomb explosion at Trinity Flats, White Sands, New Mexico
.
Lechatelierite is a mineraloid
as it does not have a crystal structure
. Although not a true mineral, it is often classified in the quartz mineral group.
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
sand during a lightning
Lightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
strike. The result is an irregular, branching, often foamy hollow tube of silica glass called a fulgurite
Fulgurite
Fulgurites are natural hollow glass tubes formed in quartzose sand, or silica, or soil by lightning strikes. They are formed when lightning with a temperature of at least instantaneously melts silica on a conductive surface and fuses grains together; the fulgurite tube is the cooled product...
.
Lechatelierite also forms as the result of high pressure shock metamorphism
Shock metamorphism
Shock metamorphism or impact metamorphism describes the effects of shock-wave related deformation and heating during impact events. The formation of similar features during explosive volcanism is generally discounted due to the lack of metamorphic effects unequivocally associated with explosions...
during meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
impact cratering
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
and is a common component of a type of glassy ejecta
Ejecta
Ejecta can mean:*In volcanology, particles that came out of a volcanic vent, traveled through the air or under water, and fell back on the ground surface or on the ocean floor...
called tektite
Tektite
Tektites are natural glass rocks up to a few centimeters in size, which most scientists argue were formed by the impact of large meteorites on Earth's surface. Tektites are typically black or olive-green, and their shape varies from rounded to irregular.Tektites are among the "driest" rocks, with...
s. Most tektites are blobs of impure glassy material, but tektites from the Sahara Desert
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...
in Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
and Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, known as Libyan desert glass
Libyan desert glass
Libyan desert glass , or great sand sea glass is a substance found in areas in the Libyan Desert. Fragments of desert glass can be found over large areas, up to tens of kilometers.- Geologic origin :...
, are composed of almost pure silica, that is almost pure lechatelierite. High pressure experiments have shown that shock pressures of 85 GPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
are needed to produce lechatelierite in quartz grains embedded in granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
.
Lechatelierite was formed during the impact of a meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
into a layer of Coconino Sandstone
Coconino Sandstone
Coconino Sandstone is a geologic formation named after its exposure in Coconino County, Arizona. This formation spreads across the Colorado Plateau province of the United States, including northern Arizona, northwest Colorado, Nevada, and Utah....
at Meteor Crater
Meteor Crater
Meteor Crater is a meteorite impact crater located approximately east of Flagstaff, near Winslow in the northern Arizona desert of the United States. Because the US Department of the Interior Division of Names commonly recognizes names of natural features derived from the nearest post office, the...
in Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
. It was puffed up to more than twice its size by steam and can now float on water.
Lechatelierite may also form artificially, a unique example being the trinitite
Trinitite
Trinitite, also known as Atomsite or Alamogordo Glass, is the name given to the glassy residue left on the desert floor after the plutonium-based Trinity nuclear bomb test on July 16, 1945, near Alamogordo, New Mexico...
produced by melting of quartz sand at the first nuclear bomb explosion at Trinity Flats, White Sands, New Mexico
White Sands, New Mexico
White Sands is a census-designated place in Doña Ana County, New Mexico, United States. The population was 1,323 at the 2000 census. It is part of the Las Cruces Metropolitan Statistical Area...
.
Lechatelierite is a mineraloid
Mineraloid
A mineraloid is a mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an amorphous glass and not a crystal. Jet is derived from decaying wood under...
as it does not have a crystal structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
. Although not a true mineral, it is often classified in the quartz mineral group.