IMCA Insights – June 2007
Our Favorite Iron Meteorites, Part 1
by the IMCA Board of Directors

In the previous issues of IMCA Insights 2007 we introduced you to Our Favorite Chondrites and to Our Favorite Achondrites. This overview wouldn't be complete without mentioning Our Favorite Iron Meteorites of the IMCA Board Members, something we would like to start in this issue. As in the past issues you will notice that our preferences are rather distinct, but nonetheless interesting. Enjoy!

Peter Marmet:

In 1984 a farmer from the Twannberg region (near Bern, Switzerland) called Mr. Rolf Buehler (Swiss Meteorite Lab) and told him that he had found a rather weird and very heavy „stone“ in a barley field while ploughing. Mr. Buehler checked the stone and found out that it was an iron meteorite of 15,915 kg. It was classified an ungrouped iron until the year 2000 when Guanaco was found in the Atacama desert in Chile. Guanaco was the fifth member of a compositional grouplet formerly known as the Bellsbank Quartet: Bellsbank, La Primitiva, Tombigbee River and Twannberg. Guanaco provided the missing part to establish a new iron chemical group, and Dr. John T. Wasson proposed, that this new iron group be given the designation IIG.

Twannberg I, 29.80g with original NMBE label

From the Twannberg I mass, 29.80g with original NMBE label,
Coll. Peter Marmet

In 2000 Marc Jost was in the attic of a friend‘s house in Twann. Before he left the attic, he noticed a strange rusty iron piece of about 2 kilos on top of a wall. The owner of the house told Marc to keep it. So he kept it for some time and he even took it with him when he went to the nearby pub for a beer. Marc showed the iron to his colleagues and told them that he had found a meteorite and everybody had a good laugh. One day Marc decided to call the Natural History Museum in Bern (NMBE). Dr. Beda Hofmann, head of the Earth Sciences Department, answered the phone. Marc Jost told his story and Dr. Hofmann was quite sure to hear another story of a meteorwrong. At the end of the short conversation Mr. Hofmann said: By the way, where are you calling from? Marc answered: From Twann! Mr. Hofmann asked quickly for Marc‘s address and less than an hour later the doorbell rang and Mr. Hofmann stood in front of Marc‘s house. Marc‘s iron was indeed the Twannberg II mass of 2246 grams!
Mass III (2533 g) was identified in September 2005 in a rock and mineral collection deposited at NMBE as a permanent loan from the Museum Schwab, Biel, Switzerland, where the sample was originally labelled as “hematite,” many years ago. Both secondary find places are in the vicinity (3.5 and 5 km distance) of the original find locality. The majority of the original mass (10,536 of 15,915 g) and both newly recovered masses are located at NMBE. The total known mass of Twannberg now is 20,694 g.

Peter Marmet at Twannberg

From here it's only a few hundred meters to the place where the
Twannberg I mass was found

Today, Marc Jost is a passionate meteorite aficionado and the proud owner of a great meteorite collection. He is convinced to find the Twannberg IV mass one day. Good luck, Marc!

Jeff Kuyken:

The Youndegin iron meteorite was originally discovered during 1884 in the form of four pieces with weights of 2.7kg, 7.9kg, 10.9kg and 11.7kg. They were found 1.2km Northwest of Penkarring Rock and 112km East of York. In 1891 another mass of 173.5kg, and in 1892 a still larger mass of 927kg were also found. Another huge meteorite of 2625.3kg was found Southwest of Quairading, in the vicinity of Wamensking Well, and is now assigned to this fall. A further mass of about 92kg was located 40km Southeast of Mount Stirling and is also assigned to this fall. A mass of 1.6kg was found in about 1893, 97km East of York plus two further masses of 820g and 742g. These three were referred to the Mooranoppin fall, which is now considered to be synonymous with Youndegin. It was actually named Youndegin after a police station which was the last outpost of civilisation at the time.
Despite the exceptional amount of material discovered, virtually nothing has ever made it into private collections. Because this meteorite was discovered a considerable time ago over such a vast area, many of the pieces were initially named under their own fall. The common synonyms for Youndegin include Quairading, Penkarring Rock, Mount Stirling and Mooranoppin. The Total Known Weight of all the Youndegin pieces is in excess of 3850kg.
Youndegin is an IAB iron meteorite and has been classified twice somewhat similarly as a Coarse (Og) and Coarsest (Ogg) Octahedrite with a Nickel content of 6.8%. The main constituent is the nickel alloy kamacite, in regular well defined plates arranged parallel to the faces of a regular octahedron. The widths of the plates vary from 1.5mm to 5mm but the average Widmanstätten Bandwidth has been determined to be approximately 2.3mm. Simpson (1938) examined Youndegin and observed Cohenite was “irregularly distributed as rather thick tablets and ragged grains”. Schreibersite was fairly evenly distributed over the etched surface as small irregular plates.

A 76.1g Full Slice of Youndegin, IAB Iron

A 76.1g Full Slice of Youndegin, IAB Iron Meteorite

This specimen is a 76.1g Complete Slice which has been professionally restored/prepared and is part of the Meteorites Australia Collection (MA.05.0035).

Mark Bostick:

The Seymchan meteorite was discovered in the Magadan district of Russia during 1967 (62° 54' N., 152° 26' E.) by an expedition of Russian scientists, headed by E. L. Krinov. A 272.3 kg stone was originally discovered and a 50 kg stone was found shortly after, but further searching was stopped by snow as winter started early. Seymchan was classified as a coarse octahedrite (IIE) iron meteorite and for almost 40 years the classification would go unchallenged.
During 2004 a new expedition spent several weeks camped in the region and a number of new Seymchan meteorites were found. Some several kilos, and others just a few ounces. It was then discovered that the meteorite was part iron and part stone, a pallasite. Not unlike the Brenham pallasite, which you can also find in complete iron specimens. Since these finds Seymchan has been officially reclassified as an ungrouped iron.

A 520g Full Slice of Seymchan - Iron or Pallasite?

A 520g Full Slice of Seymchan, Mark Bostick Collection

What makes the siderite specimens of Seymchan so interesting to me is the unusual pattern slices have. It almost appears as though someone picked up the iron right before it cooled and twisted it ... several times.
IMCA Director Andrzej S. Pilski compared content of Ni, Ge, Ga, Ir in Seymchan with data for pallasites and found they match well. "It nicely resembles pattern of Glorieta. That's why I suspected Seymchan can be pallasite even before I could see slices with olivine. I did ask Dr. Wasson and he confirmed, that indeed Seymchan is main group pallasite."
IIE’s often contain numerous inclusions of different iron rich silicates and Seymchan is full of them. Some slices of Seymchan are so rich with silicates they remind me of a mesosiderite. Perhaps this is why Seymchan has been giving an ungrouped iron tag, rather than a pallasite? Whatever scientists eventually decide Seymchan is, it is one of the more interesting and best priced meteorites on the market.

Ron Hartman:

Lake Murray (Coarsest Octahedrite, IIB, TKW: 2401 g) is one of my favorite irons. Not only because of its unique history, age, and unique structure, but also because I have had the opportunity to have several slices pass through my hands, residing either temporarily as semi-permanent members of my personal collection, or as pieces commissioned from collectors to my son, Jim, and I, for repair and restoration. The Lake Murrays we have had were all initially unstable and "rather oozy". Given patience, though, we were able to "tame" all of them and those that we have kept tabs on over a period of 6-7 years, including two large slices we now own, have continued to remain in stable condition, with no deterioration.
Lake Murray was found in 1933 in Oklahoma, weathering out of Cretaceous sandstone with a 120 million year terrestrial age, making it the oldest iron meteorite found on Earth. Several good historical accounts appear in the literature.

A 2401 gram Lake Murray Iron Full Slice

A 2401 gram Lake Murray Iron, R. N. Hartman Collection

Our specimens, including the one you see in the picture here, were deep etched with our modified Ferric Chloride process. Widmanstatten bands are large, and vary considerably in both width and shape. Large troilite nodules, commonly more than an inch across are common and swirls of schreibersite crystals, bordered with bands of kamacite are abundant. Graphite nodules are present, sometimes peppered with tiny specks of metal.

Anne Black:

My favorite iron is Burns. Two to three years ago, I received an email. As in so many other emails, the writer was telling me about a brand-new meteorite. This time the writer was a woman, working for a college in southern Colorado, and the supposed meteorite had been found high in the Rockies. That was unusual enough that I looked at the picture attached to the email.

The new Burns iron meteorite in as found condition

The New Burns Iron Meteorite in as found condition

The picture was not encouraging, a large ugly mass on a concrete driveway with a tape measure. It looked burned, rusty. Probably some slag from some mining operation. Still, being polite, I pointed her to the website of the Northern Arizona University and suggested that she wrote to Dr. Ted Bunch. The picture stayed on my hard-drive, but frankly I forgot all about it quickly. There were other emails, and other new "discoveries".
Then in early December 2006, I received another email from the same writer, thanking me for my help, and happy to tell me that it was indeed a meteorite, a fine octahedrite. I will admit that it took me a while to figure out who the writer was and what meteorite we were talking about. Then she informed me that her family had decided to sell the meteorite, that they would be in Denver in a few days, and could I possibly help them. Of course, less than 2 weeks later, they were in my living room.
I was glad to meet them and hear all about the circumstances of the discovery; we agreed on a price quickly and easily and they left me with a heavy rusty mass wrapped in a pink bath towel. The next day I carried it, still in the towel to a meeting of the COMETS (COlorado METeorite Society) where we all examined it, under all angles until someone tried to stand it on end. And it did stand nicely and then we noticed that there was almost a face there, in profile. At the end of the meeting, Fred Hall was kind enough to volunteer to take it home and cleaned it up.

The Face of "Mr. Burns"

The Face of "Mr. Burns" - do you see it?

A few days later it was returned to me, still wrapped in its pink towel, but the caliche was gone, it do longer dripped rust and shale. And the face was clearly visible, a long nose, deep-set eye, a curl of hair on a low forehead. It had developed a personality, and acquired a nickname, Mister Burns.

In the August issue of IMCA Insights we will present you with Our Favorite Irons, Part 2 - the July issue is reserved for our special Ensisheim Meteorite Show 2007 Report. Stay tuned, and thanks for your interest!

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