Maskelynite
Encyclopedia
Maskelynite is a glass
y phase
found in some meteorite
s and meteorite impact crater
s. Typical samples are similar in composition to plagioclase
feldspar
, and revert to that mineral when melted and recrystallized. It was named after British
geologist
M.H.N. Story-Maskelyne
.
The Dhofar 378 meteorite is 47% maskelynite by volume.
by G. Tschermak
(1872) as an isotropic glass of an unknown origin with
near labradorite
composition. Similar phases were found in chondrites and Martian (SNC) meteorite
s. In 1963, D. J. Milton and P. S. de Carli produced a maskelynite-like glass by subjecting gabbro
to an explosive shock wave
. In 1967, T. E. Bunch and others identified maskelynite in the Clearwater West
and Manicouagan crater
s.
(250 to 300 kilobars) and low-temperature (350 °C
), as in Milton and de Carli's experiment. Since 1997 this hypothesis has been challenged, and now it is believed that the glass is formed by the quenching of dense mineral melts produced by higher-pressure shock waves.
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
y phase
Phase (matter)
In the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, and chemical composition...
found in some 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...
s and meteorite impact crater
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...
s. Typical samples are similar in composition to plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
feldspar
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
, and revert to that mineral when melted and recrystallized. It was named after British
British people
The British are citizens of the United Kingdom, of the Isle of Man, any of the Channel Islands, or of any of the British overseas territories, and their descendants...
geologist
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
M.H.N. Story-Maskelyne
Nevil Story Maskelyne
Mervyn Herbert Nevil Story Maskelyne was an English geologist and politician.-Scientific career:Educated at Wadham College, Oxford, Maskelyne taught mineralogy and chemistry at Oxford from 1851, before becoming a professor of mineralogy, 1856-95. He was Keeper of Minerals at the British Museum...
.
The Dhofar 378 meteorite is 47% maskelynite by volume.
History
The phase was first identified in the Shergotty meteoriteShergotty meteorite
The Shergotty meteorite is the first example of the shergottite Mars meteorite family. It was a Martian meteorite which fell to Earth at Shergotty , in the Gaya district, Bihar, India on 25 August 1865, and was retrieved by witnesses almost immediately...
by G. Tschermak
Gustav Tschermak von Seysenegg
Gustav Tschermak von Seysenegg was an Austrian mineralogist.-Biography:He was born 19 April 1836 in Littau, Olomouc District, Moravia and studied at the University of Vienna where he obtained a teaching degree. He studied mineralogy at Heidelberg and Tübingen and obtained a PhD...
(1872) as an isotropic glass of an unknown origin with
near labradorite
Labradorite
Labradorite , a feldspar mineral, is an intermediate to calcic member of the plagioclase series. It is usually defined as having "%An" between 50 and 70. The specific gravity ranges from 2.68 to 2.72. The streak is white, like most silicates. The refractive index ranges from 1.559 to 1.573....
composition. Similar phases were found in chondrites and Martian (SNC) meteorite
Mars meteorite
A martian meteorite is a rock that formed on the planet Mars, was ejected from Mars by the impact of an asteroid or comet, and landed on the Earth. Of over 53000 meteorites that have been found on Earth, 99 are martian...
s. In 1963, D. J. Milton and P. S. de Carli produced a maskelynite-like glass by subjecting gabbro
Gabbro
Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....
to an explosive shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
. In 1967, T. E. Bunch and others identified maskelynite in the Clearwater West
Clearwater Lakes
The Lac à l'Eau Claire , also called the Clearwater Lakes in English, Wiyasakami in Cree and Allait Qasigialingat by the Inuit, are a pair of circular lakes on the Canadian Shield in Quebec, Canada, near Hudson Bay.The lakes are actually a single body of water with a sprinkling of islands forming a...
and Manicouagan crater
Manicouagan crater
The Manicouagan Crater is one of the oldest known impact craters and is located primarily in Manicouagan Regional County Municipality in the Côte-Nord region of Québec, Canada, about north of the city of Baie-Comeau. Its northernmost part is located in Caniapiscau Regional County Municipality...
s.
Origin
At first, maskelynite was believed to result from solid-state transformation of plagioclase into diaplectic glass by a relatively low-pressure shock waveShock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
(250 to 300 kilobars) and low-temperature (350 °C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
), as in Milton and de Carli's experiment. Since 1997 this hypothesis has been challenged, and now it is believed that the glass is formed by the quenching of dense mineral melts produced by higher-pressure shock waves.