The Twannberg meteorite is a

hexahedrite Hexahedrites are a structural class of iron meteorite. They are composed almost exclusively of the nickel–iron alloy kamacite and are lower in nickel content than the octahedrites. The nickel concentration in hexahedrites is always below 5.8% and ...

iron meteorite Iron meteorites, also known as siderites, or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most i ...

. It is the only meteorite of the IIG group found in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...

and the largest meteorite ever found in Switzerland.

Discovery and naming

The first fragment () was found on 9 May 1984 in a barley field near

Twann Twann (french: Douanne ) was a municipality in the district of Nidau in the canton of Bern in Switzerland. On 1 January 2010 the municipalities of Tüscherz-Alfermée and Twann merged into the municipality of Twann-Tüscherz. History Twann ...

, after it had been ploughed (Twannberg I). Two additional fragments were found in an unnatural setting. One fragment (II) was found in 2000 in an attic in

and another (III) in 2005 in the Naturhistorisches Museum Bern, in a collection received from the Museum Schwab in Biel where it had been labeled as hematite around 1930. Twannberg IV, V and VI were found in the creek Twannbach. The meteorite is named after Twannberg (from German: Twann mountain), a mountain that lies north of

The find location is a glacial till deposit. This paired with minerals found in the oxidized surface of the meteorite are an indicator that the meteorite fell on the Rhone glacier and was transported by it to

during the

Würm ice age The Würm is a river in Bavaria, Germany, right tributary of the Amper. The length of the river is , or including the ''Steinbach'', the main feed of Lake Starnberg. It drains the overflow from Lake Starnberg and flows swiftly through the villag ...

and then deposited there.

Mineralogy

The meteorite is composed of

meteoric iron Meteoric iron, sometimes meteoritic iron, is a native metal and early-universe protoplanetary-disk remnant found in meteorites and made from the elements iron and nickel, mainly in the form of the mineral phases kamacite and taenite. Meteoric i ...

and

schreibersite Schreibersite is generally a rare iron nickel phosphide mineral, , though common in iron-nickel meteorites. It has been found on Disko Island in Greenland and Illinois. Another name used for the mineral is rhabdite. It forms tetragonal crystals w ...

. The meteoric iron has 5.1%

Nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...

, and is all in the form of

kamacite Kamacite is an alloy of iron and nickel, which is found on Earth only in meteorites. According to the International Mineralogical Association (IMA) it is considered a proper nickel-rich variety of the mineral native iron. The proportion iron:ni ...

. The preatmospheric mass was estimated to be at least . The surface of the meteorite is covered in an oxidation layer.

Classification

The meteorite is classified as a member of group IIG.

References

{{Meteorites by name Meteorites found in Switzerland

Discovery and naming

Mineralogy

Classification

See also

References