Pallasite
Encyclopedia
A pallasite is a type of stony–iron meteorite.
crystals of peridot
quality in an iron-nickel
matrix
. Coarser metal areas develop Widmanstätten pattern
s upon etching. Minor constituents are schreibersite
, troilite
, chromite, pyroxenes, and phosphates (whitlockite, stanfieldite, farringtonite, and merrillite).
s that were subsequently shattered through impacts. An alternative recent hypothesis is that they are impact-generated mixtures of core and mantle materials.
A common error is to associate their name with the asteroid 2 Pallas
but their actual name is after the German naturalist Peter Pallas
(1741–1811), who studied in 1772 a specimen found earlier near Krasnoyarsk
in the mountains of Siberia
that had a mass of 680 kg. The Krasnoyarsk mass described by Pallas in 1776 was one of the examples used by E.F.F. Chladni in the 1790s to demonstrate the reality of meteorite falls on the Earth, which were at his time considered by most scientists as fairytales. This rock mass was dissimilar to all rocks or ores found in this area (and the large piece could not have been accidentally transported to the find site), but its content of native metal was similar to other finds known from completely different areas.
Structure and composition
It consists of cm-sized olivineOlivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
crystals of peridot
Peridot
-Chemistry:The chemical composition of peridot is 2SiO4, with Mg in greater quantities than Fe.-Etymology:The origin of the name "peridot" is uncertain...
quality in an iron-nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
matrix
Matrix (geology)
The matrix or groundmass of rock is the finer grained mass of material in which larger grains, crystals or clasts are embedded.The matrix of an igneous rock consists of finer grained, often microscopic, crystals in which larger crystals are embedded. This porphyritic texture is indicative of...
. Coarser metal areas develop Widmanstätten pattern
Widmanstätten pattern
Widmanstätten patterns, also called Thomson structures, are unique figures of long nickel-iron crystals, found in the octahedrite iron meteorites and some pallasites. They consist of a fine interleaving of kamacite and taenite bands or ribbons called lamellæ...
s upon etching. Minor constituents are schreibersite
Schreibersite
Schreibersite is generally a rare iron nickel phosphide mineral, 3P, though common in iron-nickel meteorites. It is rarely reported from Earth . Another name used for the mineral is rhabdite. It forms tetragonal crystals with perfect 001 cleavage. Its color ranges from bronze to brass yellow to...
, troilite
Troilite
Troilite is a rare iron sulfide mineral with the simple formula of FeS. It is the iron rich endmember of the pyrrhotite group. Pyrrhotite has the formula FeS which is iron deficient...
, chromite, pyroxenes, and phosphates (whitlockite, stanfieldite, farringtonite, and merrillite).
Classification and subgroups
Using the oxygen isotopic composition, pallasites are divided into 3 subgroups.- Main group (MG): almost all pallasites
- Eagle Station group (ES): counts only Eagle Station, Cold Bay and Itzawisis pallasites. Olivine is rich in iron and the metal matrix is rich in nickelNickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
. They are related to IIF irons. - Pyroxene group (PX): counts only Vermillion and Yamato 8451. Take its name from the high orthopyroxene content (about 5%). Metal matrix shows a fine octahedrite Widmanstätten pattern.
Origin
Pallasites were once thought to originate at the core-mantle boundary of differentiated asteroidAsteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
s that were subsequently shattered through impacts. An alternative recent hypothesis is that they are impact-generated mixtures of core and mantle materials.
History
2 Pallas
Pallas, formally designated 2 Pallas, is the second asteroid to have been discovered , and one of the largest. It is estimated to constitute 7% of the mass of the asteroid belt, and its diameter of 530–565 km is comparable to, or slightly larger than, that of 4 Vesta. It is however 20%...
but their actual name is after the German naturalist Peter Pallas
Peter Simon Pallas
Peter Simon Pallas was a German zoologist and botanist who worked in Russia.- Life and work :Pallas was born in Berlin, the son of Professor of Surgery Simon Pallas. He studied with private tutors and took an interest in natural history, later attending the University of Halle and the University...
(1741–1811), who studied in 1772 a specimen found earlier near Krasnoyarsk
Krasnoyarsk
Krasnoyarsk is a city and the administrative center of Krasnoyarsk Krai, Russia, located on the Yenisei River. It is the third largest city in Siberia, with the population of 973,891. Krasnoyarsk is an important junction of the Trans-Siberian Railway and one of Russia's largest producers of...
in the mountains of Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
that had a mass of 680 kg. The Krasnoyarsk mass described by Pallas in 1776 was one of the examples used by E.F.F. Chladni in the 1790s to demonstrate the reality of meteorite falls on the Earth, which were at his time considered by most scientists as fairytales. This rock mass was dissimilar to all rocks or ores found in this area (and the large piece could not have been accidentally transported to the find site), but its content of native metal was similar to other finds known from completely different areas.
Pallasite falls
Pallasites are a rare type of meteorite. Only 61 are known to date, including 10 from Antarctica, with four being observed falls. The following four falls are in chronological order:- MineoMineo (meteorite)There are only 4 witnessed fall pallasite meteorites in the world and Mineo is one of them. It was also the first pallasite meteorite from Italy.-History:...
, SicilySicilySicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
, ItalyItalyItaly , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
. A luminous meteor was observed and an object seen to fall with a loud roar in May 1826. Only 46 g are preserved in collections. - Zaisho, JapanJapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. 330 g were found on February 1, 1898, after the appearance of a fireball. - Marjalahti, KareliaKareliaKarelia , the land of the Karelian peoples, is an area in Northern Europe of historical significance for Finland, Russia, and Sweden...
, RussiaRussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. After the appearance of a bright meteor and detonations, a large mass was seen to fall and 45 kg were recovered in June 1902. At this date the fall site belonged to FinlandFinlandFinland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
, and the main mass of Marjalahti is now at the Geological Museum of the University of HelsinkiHelsinkiHelsinki is the capital and largest city in Finland. It is in the region of Uusimaa, located in southern Finland, on the shore of the Gulf of Finland, an arm of the Baltic Sea. The population of the city of Helsinki is , making it by far the most populous municipality in Finland. Helsinki is...
. - OmolonOmolon (meteorite)Omolon is a meteorite fallen in 1981 near Omolon , Magadan . It is a pallasite.-History:On May 16, 1981 at 5:10 there was a report from a meteorological station of a bright fireball....
, Magadan Region, RussiaRussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. A reindeer-breeder observed the fall on May 16, 1981, and found the 250 kg meteorite two years later. The fall was confirmed by a meteorological station that had observed a fireball on the same date.
Notable pallasite finds
Although pallasites are a rare meteorite type, enough pallasite material is found in museums and meteorite collections and is available for research. This is due to large finds, some of which yielded more than a metric ton. The following are the largest finds:- BrenhamBrenham (meteorite)Brenham is a pallasite meteorite found near Haviland, a small town between Wichita and Dodge City in Kansas. Pallasites are a type of stony–iron meteorite that when cut and polished show beautiful yellowish olivine crystals.-History:...
, KansasKansasKansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
, USA. In 1890 the find of about 20 masses with a total weight of 1000 kg around the shallow Haviland CraterHaviland CraterThe Haviland Crater, also called the Brenham Crater, is a meteorite crater in Kiowa County, Kansas.The oval-shaped crater is 50 feet in diameter, making it one of the smallest impact craters in the world. Its age is estimated to be less than 1000 years...
were reported. More masses were found later, including one of 454 kilograms (1,000.9 lb) from a depth of 5 feet (1.5 m), the total amounting to about 4.3 tonnes (4.2 LT). A piece of 487 kg is in the Field Museum of Natural HistoryField Museum of Natural HistoryThe Field Museum of Natural History is located in Chicago, Illinois, USA. It sits on Lake Shore Drive next to Lake Michigan, part of a scenic complex known as the Museum Campus Chicago...
, Chicago. In 2005, Steve Arnold of Arkansas, USA, and Phil Mani of Texas, USA, unearthed a large mass of 650 kg and in 2006 several new large masses - HuckittaHuckittaHuckitta is a pallasite meteorite recovered in 1937 from Huckitta Cattle Station, Northern Territory, Australia.-History:In 1924 a meteoritic mass of 1084 grams was found by Herbert Basedow on Burt Plain , about 17 km north of Alice Springs. This mass was called Alice Springs...
, Northern TerritoryNorthern TerritoryThe Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. A mass of 1400 kg was found in 1937 on a cattle station north-east of Alice Springs. Earlier, in 1924, a transported piece of about 1 kg had been found on Burt Plain north of Alice Springs. - Fukang, Xinjiang Province, ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. A mass of 1003 kg was recovered in 2000. - ImilacImilacImilac is the name given to a pallasite meteorite found in the Atacama Desert of Northern Chile in 1822.- Classification :Imilac is classified as a stony–iron pallasite. Imilac specimens are highly prized by meteorite collectors due to its high concentration of beautiful olivine grains.- Strewn...
, Atacama DesertAtacama DesertThe Atacama Desert is a plateau in South America, covering a strip of land on the Pacific coast, west of the Andes mountains. It is, according to NASA, National Geographic and many other publications, the driest desert in the world...
, ChileChileChile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
; known since 1822. Numerous masses up to 200 kg were found, the total weight is about 920 kg. - BrahinBrahin (meteorite)Brahin is a meteorite pallasite found in 1807.This is the second meteorite ever found in Russia.Sometimes it is also called Bragin or Bragim.It is quite common among collectors due the affordable price of small partial slices.-History:...
, Gomel Region, BelarusBelarusBelarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...
, known since 1810. Many masses were found in a strewnfield, with a total weight of about 820 kg. An additional mass of 227 kg was found at a depth of 10 feet (3 m) in 2002. - EsquelEsquel (meteorite)Esquel is a pallasite meteorite found near Esquel, a patagonian town in the northwest part of the province of Chubut . Pallasites are a type of stony–iron meteorite that when cut and polished show beautiful yellowish olivine crystals....
, ChubutChubut ProvinceChubut a province in the southern part of Argentina situated between the 42nd parallel south and the 46th parallel south , the Andes range separating Argentina from Chile, and the Atlantic ocean...
, ArgentinaArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. A large mass of 755 kg was found embedded in soil before 1951. - PallasovkaPallasovka (meteorite)Pallasovka is a pallasite meteorite found in 1990 near the town of Pallasovka, Russia.-History:One single mass of 198 kg was found 27.5 km from the town of Pallasovka by N. F. Kharitonov on a dike on the edge of an artificial water reservoir...
, PallasovkaPallasovkaPallasovka is a town and the administrative center of Pallasovsky District of Volgograd Oblast, Russia, located on the Torgun River , northeast of Volgograd. Population: -History:...
, RussiaRussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. A single mass of 198 kg was found near Pallasovka, Russia in 1990. Coincidentally, both the town of Pallasovka and pallasite meteorites were named after the naturalist, Peter Pallas. - KrasnojarskKrasnojarsk (meteorite)-History:A mass of about 700 kg was detected in 1749 about 145 miles south of Krasnoyarsk. It was seen by P.S. Pallas in 1772 and then on his orders transported to Saint Petersburg....
, Yeniseisk, RussiaRussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. A mass of about 700 kg was detected in 1749 about 145 miles (233.4 km) south of Krasnojarsk. It was seen by P. S. PallasPeter Simon PallasPeter Simon Pallas was a German zoologist and botanist who worked in Russia.- Life and work :Pallas was born in Berlin, the son of Professor of Surgery Simon Pallas. He studied with private tutors and took an interest in natural history, later attending the University of Halle and the University...
in 1772 and transported to Krasnojarsk (see above) The main mass of 515 kg is now in Moscow at the Academy of Sciences. Pallasites are named after Peter Pallas for his study of this meteorite. - Conception Junction, MissouriConception Junction, MissouriConception Junction is a city in Nodaway County, Missouri, United States, near the Platte River. The population was 202 at the 2000 census, at which time it was a town.-Geography:...
, USA, a 17-kilogram pallasite meteorite found by a farmer; an "unusually heavy stone" buried deep in a hillside in 2006.
External links
- Pallasite images from Meteorites Australia - Meteorites.com.au
- (AP) "Unusual meteorite found in wheat field" October 17, 2006
- Legend of Glorieta Mountain Discovery of a large pallasite in New Mexico