Mesosiderite

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Mesosiderite
Mesosiderite

Mesosiderites are a class of stony-iron meteorites consisting of about equal parts of metallic nickeliron and silicate. They are breccias 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 eucrites and diogenites.

They are a rare type of meteorites, until now (February 2006) only 86 are known, 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 were found in a large strewnfield, with a total mass of 3.8 tons. They were first discovered in the 19th century by ore prospectors. They mistook the shiny metal inclusions for silver and thought they had found the outcrop of a silver ore. Only later an analysis was made and nickeliron found, and the true nature as a meteorite was established. 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, totalling 320 kg. Also 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 Veramin (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.

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