Twannberg - Fer, IIG - Suisse

TW96, a 257.8g complete individual of Twannberg, still carrying its original field label. It was found by Sergey Vasiliev on 27th June 2014 at 47° 07.370'N, 7° 10.565'E, one of the first meteorites recovered during the systematic search of the strewn field, and its find details are published in the Hofmann, Jost and Koppelt book documenting the Twannberg search. By our count, only 27 of the first 570 numbered finds listed there are larger. It has been kept in its original as-found condition, with only loose soil removed, and has remained stable since recovery. On request, we can transfer it into the new owner's name in the Meteorite Studies Collection Database.

Twannberg is a IIG Iron meteorite from the Swiss Jura Mountains, a few kilometres west of Biel in the Canton of Bern. The first mass, weighing 15.9kg, was a chance find in 1984, and since 2000 searchers have recovered more than 2,000 further pieces from a strewn field of around 10 square kilometres. Measurements of cosmogenic isotopes place the fall at roughly 176,000 years ago, during the penultimate glacial period.

IIG irons are among the rarest of the iron meteorite groups. They are hexahedrites with the lowest nickel content of any iron meteorites, around 4.5% in the metal, and Twannberg is the only well-documented IIG strewn field on Earth. Having lain for so long in glacial sediments and soils, Twannberg specimens typically show weathered, rust-brown exteriors with sculpted hollows and patches of dark oxide, while the metal within remains sound.

For collectors, Twannberg combines a rare iron group with exceptional documentation. Many finds from the systematic search carry their original field numbers, and their recovery points have been recorded and published, so individual specimens can be traced back to the exact spot where they were found. Each piece is a genuine fragment of a IIG iron that fell on the Swiss Jura long before the last Ice Age.