Mesosiderite
Encyclopedia
Mesosiderites are a class of stony–iron meteorites consisting of about equal parts of metallic nickel-iron and silicate
. They are breccia
s with an irregular texture; silicates and metal occur often in lumps or pebbles as well as in fine-grained intergrowths. The silicate part contains olivine
, pyroxenes, and Ca-rich feldspar
and is similar in composition to eucrite
s and diogenite
s.
They are a rare type of meteorite; as of June 2011 only 167 are known (of which 51 come from Antarctica) and only 7 of these are observed falls. On the other hand, some mesosiderites are among the largest meteorites known.
At Vaca Muerta in the Atacama Desert
in Chile
, many fragments with a total mass of 3.8 tons were found in a large strewnfield. They were first discovered in the 19th century by ore prospector
s who mistook the shiny metal inclusions for silver
and thought they had found an outcrop of a silver ore deposit. Later when an analysis was made and nickel-iron was found, the true nature as a meteorite was established. The meteorite was called Vaca Muerta. The picture at right shows a cut and polished piece of Vaca Muerta.
The most recent fall of a mesosiderite occurred at Dong Ujimqin Qi in China, on September 7, 1995, where three large pieces with a total mass of 129 kg fell. The fall of the Estherville mesosiderite in Iowa, USA occurred on May 10, 1879. After a brilliant fireball had been seen, a shower of several large masses and many small fragments fell, totaling 320 kg. The fall at Lowicz in Poland on March 12, 1935 yielded many (more than 50) fragments with a total weight of 59 kg. The other observed mesosiderite falls occurred in 1842 at Barea (Spain), in 1880 at Varamin (Iran), in 1933 at Dyarrl Island (Papua New Guinea), and at Patwar (India) in 1935.
The legendary Chinguetti meteorite
is also supposed to be a mesosiderite.
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
. They are breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
s with an irregular texture; silicates and metal occur often in lumps or pebbles as well as in fine-grained intergrowths. The silicate part contains olivine
Olivine
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....
, pyroxenes, and Ca-rich feldspar
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
and is similar in composition to eucrite
Eucrite
Eucrites are achondritic stony meteorites, many of which originate from the surface of the asteroid 4 Vesta and as such are part of the HED meteorite group. They are the most common achondrite group with well over 100 distinct finds at present....
s and diogenite
Diogenite
Diogenites are a subgroup of the HED meteorite group, a type of achondritic stony meteorites.-Origin and composition:Diogenites originates from deep within the crust of the asteroid 4 Vesta, and as such are part of the HED meteorite group...
s.
They are a rare type of meteorite; as of June 2011 only 167 are known (of which 51 come from Antarctica) and only 7 of these are observed falls. On the other hand, some mesosiderites are among the largest meteorites known.
At Vaca Muerta in the Atacama Desert
Atacama Desert
The 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...
in Chile
Chile
Chile ,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...
, many fragments with a total mass of 3.8 tons were found in a large strewnfield. They were first discovered in the 19th century by ore prospector
Prospecting
Prospecting is the physical search for minerals, fossils, precious metals or mineral specimens, and is also known as fossicking.Prospecting is a small-scale form of mineral exploration which is an organised, large scale effort undertaken by mineral resource companies to find commercially viable ore...
s who mistook the shiny metal inclusions for silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
and thought they had found an outcrop of a silver ore deposit. Later when an analysis was made and nickel-iron was found, the true nature as a meteorite was established. The meteorite was called Vaca Muerta. The picture at right shows a cut and polished piece of Vaca Muerta.
The most recent fall of a mesosiderite occurred at Dong Ujimqin Qi in China, on September 7, 1995, where three large pieces with a total mass of 129 kg fell. The fall of the Estherville mesosiderite in Iowa, USA occurred on May 10, 1879. After a brilliant fireball had been seen, a shower of several large masses and many small fragments fell, totaling 320 kg. The fall at Lowicz in Poland on March 12, 1935 yielded many (more than 50) fragments with a total weight of 59 kg. The other observed mesosiderite falls occurred in 1842 at Barea (Spain), in 1880 at Varamin (Iran), in 1933 at Dyarrl Island (Papua New Guinea), and at Patwar (India) in 1935.
The legendary Chinguetti meteorite
Chinguetti meteorite
The Chinguetti meteorite is a find reputed to come from a large unconfirmed 'iron mountain' in Africa.The existence of a huge stony-iron mesosiderite approximately 45 kilometers from the Saharan city Chinguetti, Mauritania, has been a mystery since 1916, when Captain Gaston Ripert, a French...
is also supposed to be a mesosiderite.
External links
- Mesosiderite images from Northern Arizona University
- Mesosiderite images from Meteorites Australia