Muonionalusta Iron Meteorite End Cut, IVA Fine Octahedrite, 53.41g, Etched Widmanstatten Pattern

A polished and etched end cut from an asteroid core

This 53.41g end cut of Muonionalusta has been polished and etched on its cut face to bring out the Widmanstatten pattern, the interlocking kamacite and taenite bands that grew as the nickel-iron core of a differentiated asteroid cooled. Muonionalusta is classified in the Meteoritical Bulletin as Iron, IVA, and was first recorded in the Bulletin as an iron of fine octahedrite structure.

The end cut has been fully stabilized and finished with a light protective coating. It carries no epoxy. An end cut carries one cut face, with the rest of the piece formed by the exterior of the original mass, so it shows both the internal crystal structure and the outside of the meteorite in a single specimen.

Structure and features

The Widmanstatten pattern is a three dimensional intergrowth of two nickel-iron alloys. Kamacite, which is low in nickel, formed as plates along the octahedral planes of the parent taenite crystal as the metal cooled. Etching with dilute acid attacks the two phases at different rates, so the bands stand out against each other on a polished face.

In a fine octahedrite the kamacite bands are narrow, which gives a tight, closely spaced pattern rather than the broad bands of coarser irons. The angle at which a cut crosses the original crystal determines how the bands appear on any given face, so the geometry varies from piece to piece even within the same mass.

The protective coating is applied to slow oxidation of the etched metal. Iron meteorites react with moisture, and stabilization and a sealing coat are the standard ways to protect an etched surface over time.

Discovery and provenance

Muonionalusta comes from Norrbotten in northern Sweden, where the first mass was found in 1906. The Meteoritical Bulletin records the find year as 1906, the country as Sweden, and a mass of 230 kg. That figure reflects the early finds; systematic searching in the decades since has recovered a great deal more material, so it should not be read as the total that exists today. The Bulletin itself cautions that its recorded masses are not authoritative.

This specimen was acquired by Treasure Coast Meteorite Co.

Scientific context

IVA irons are thought to come from the metallic core of a parent body that melted and separated into metal and rock early in the history of the solar system. Slow cooling of that core over a very long time allowed the kamacite and taenite to separate into the coarse crystal intergrowth that etching reveals. Later collisions broke the parent body apart and exposed core material that eventually reached Earth.

As of October 2026, the Meteoritical Bulletin lists this as 1 of 88 approved meteorites classified as Iron, IVA. That is a count of database entries; some entries may later be shown to be paired.

The story

The first piece of Muonionalusta was found in 1906 in the forests of Swedish Lapland, north of the Arctic Circle. According to the locality record, it was found by a 10 year old boy tending cattle in the forest southwest of the village of Kitkiojarvi. The meteorite takes its name from Muonionalusta, a place on the Muonio River along the border between Sweden and Finland.

The Bulletin records two of the early recoveries in its own pages. Meteoritical Bulletin 20 reports a second mass of about 15 kg, found on 15 August 1946 during earthwork at a building site roughly 8 km east southeast of the 1906 find. Meteoritical Bulletin 28 reports a third, a single 6.20 kg mass found on 7 June 1963 by Carl Henriksson in excavated material used to build a causeway, about 3.5 km east northeast of the village. That mass went to the Swedish Museum of Natural History in Stockholm.

Finds stayed slow for most of the twentieth century. Searching with metal detectors since the late 1980s has recovered many more masses from the glacial till of the region, some from several meters down. They sit in till because they have been on Earth a very long time: Holtstam and colleagues cite a terrestrial age of more than 800,000 years from cosmogenic beryllium-10 and chlorine-36, long enough for the masses to have lived through several major glaciations.

Sources: Meteoritical Bulletin 20 (1961) and 28 (1963), as reproduced in the Meteoritical Bulletin Database entry; Holtstam et al. (2003), cited below; Mindat locality record for Muonionalusta; The Muonionalusta iron meteorites from Lapland, Sweden: New finds and findings.

What the research reports

The Meteoritical Bulletin classifies Muonionalusta as Iron, IVA. Its classification history begins as Iron-fine octahedrite in Meteoritical Bulletin 20 (1961), with the IVA group assigned in the Natural History Museum Catalogue of Meteorites (2000) and in MetBase (2006). The database records iron meteorites by chemical group only, which is why the current recommended classification does not include the structural term. Fine octahedrite is used on this listing because the Bulletin's own 1961 record uses it, and because the entry links Buchwald's Handbook of Iron Meteorites (1975, volume 3, page 865) for the structural description. The studies below come from the authors' own samples and methods, and are given here as the studies state them.

Holtstam et al. (2003): stishovite in an iron meteorite

D. Holtstam, C. Broman, J. Soderhielm and A. Zetterqvist published First discovery of stishovite in an iron meteorite (Meteoritics and Planetary Science, volume 38, pages 1579 to 1583, 2003). Stishovite is a very high pressure form of silica, and Muonionalusta was the first iron meteorite in which it had been found.

Blichert-Toft et al. (2010): an early age for the IVA core

J. Blichert-Toft, F. Moynier, C.-T. A. Lee, P. Telouk and F. Albarede published The early formation of the IVA iron meteorite parent body (Earth and Planetary Science Letters, volume 296, pages 469 to 480, 2010). Lead isotopes in the troilite inclusions of Muonionalusta gave an age of 4,565.3 plus or minus 0.1 million years, placing the solidification of the IVA core within a few million years of the first solids in the solar system. The authors describe the meteorite as "heavily shocked," possibly during the breakup of the parent body about 400 million years ago.

Brennecka et al. (2018): a caveat on that age

A later study led by G. A. Brennecka, Uranium isotope ratios of Muonionalusta troilite and complications for the absolute age of the IVA iron meteorite core (Earth and Planetary Science Letters, 2018), measured the uranium isotope ratio in Muonionalusta troilite directly. The 2010 age relied on an assumed uranium isotope ratio, and the new measurements complicate the absolute age, so the 4,565.3 million year figure is best read with that caveat.

Frequently asked questions

What is the official classification?
The Meteoritical Bulletin classifies Muonionalusta as Iron, IVA. It was first recorded in Meteoritical Bulletin 20 (1961) as an iron of fine octahedrite structure. The full entry is linked at the end of this listing.

Is this specimen coated?
Yes. It has a light protective coating to help preserve the etched surface. There is no epoxy on this specimen.

Has it been stabilized?
Yes. The end cut has been fully stabilized before finishing. Stabilization reduces the risk of rust developing from within the metal, which is the main long term concern with iron meteorites.

How should I care for it?
Store it in a dry place and handle it by the edges. Skin oils and humidity are the main causes of spotting on etched iron. Avoid cleaning it with water or household cleaners.

What makes the Widmanstatten pattern visible?
Etching. The pattern is present throughout the metal, but on a cut and polished face it is not visible until a dilute acid etch attacks the kamacite and taenite at different rates and creates contrast between the bands.

What is an end cut?
An end cut is the piece taken from the end of a mass when it is sliced. It has one flat cut face, here polished and etched, and the remaining surface is the exterior of the original mass.

Is a display stand included?
No. Only the specimen is included unless otherwise stated.

Who is the seller?
Treasure Coast Meteorite Co. is an IMCA member, #3323, based in Hobe Sound, Florida.

Collector significance

Muonionalusta combines a long and well documented find history, a classification that runs back to the Bulletin's records of 1961, and a published research record that includes the first stishovite found in an iron meteorite and one of the oldest ages measured for an iron meteorite core. A 53.41g etched end cut puts all of that in a piece small enough to hold in one hand, with the cut face and the exterior of the mass side by side.

See more specimens of this meteorite in the Muonionalusta collection and other irons in the Iron Meteorites collection. For background on how the pattern forms, see the Widmanstatten pattern explained.

Meteoritical Bulletin entry: Muonionalusta. Classification: Iron, IVA. Find, Sweden, 1906. Treasure Coast Meteorite Co., IMCA #3323.