IMCA Insights – August 2007
Our Favorite Iron Meteorites, Part 2
by the IMCA Board of Directors

This is the second part of Our Favorite Iron Meteorites, introducing you to some more great samples that have a very special place in the hearts and in the collections of the IMCA Board Members. Enjoy!

Christian Anger:

Silicated irons are very beautiful and amazing when watched under the microscope. The silicated iron meteorite Udei Station has, IMHO, the most beautiful silicate inclusions of all silicated irons. Especially the wonderful green chromian-diopside crystals are marvellous.

Chromian-diopside Crystals in the Udei Station, IAB Iron Meteorite

Udei Station is a witnessed iron meteorite fall, so it is a very fresh meteorite. A 103 kg mass fell in spring 1927 near the Benue River in Nigeria. It is a IAB medium octahedrite and represents the so called "Udei Station grouplet" in the IAB complex. The silicate sizes range from single grains up to 8 cm. Udei Station contains oxidized as well as reduced phases of Cr and P (i.e. chromian-diopside, chromite-daubreelite, and phosphate-phosphides) in addition to a most oxidized silicate mineralogy. The clasts in which these minerals occur are particularly interesting since they are depleted in high-Ca pyroxene and plagioclase and are probably an olivine-rich residue formed at relatively high temperature. Chromite is scattered throughout the inclusions. Phosphates can be found completely within the inclusions, but they also occur on the edges of the inclusions, in contact with the metallic matrix.

A 239g Full Slice of the Udei Station, IAB Iron Meteorite,
Coll. Christian Anger

My collection piece is an etched 239 g slice containing some green chromian-diopside crystals and the big silicate inclusion in the middle of the slice measures 65x35mm.

Norbert Classen:

I usually don't collect iron meteorites, but I have my favorite, anyway: the anomalous, silicate-rich IVA iron Steinbach. This historic German find consists of nearly equal parts of a IVA nickel-iron matrix and reddish silicates. These silicates are a mixture of pyroxenes and the rare mineral tridymite. It is still heavily debated whether this beautiful silicated iron represents a IVA analog to the pallasites, those true stony-iron meteorites that formed at the core/mantle boundary of their parent body, or if Steinbach is just a secondary product, formed during the reaccretion of the IVA parent body following a disrupting impact.

A Slice of the Steinbach Iron; former Norbert Classen Coll. Sample

Recent research suggests that the IVA irons formed in the core of a small, differentiated asteroid that was disrupted by a major impact shortly after its formation. After the asteroid was reaccreted, it was again disrupted about 450 million years ago. What an exciting history!

Andrzej S. Pilski:

Every iron is my favourite except those totally weathered ones. However, I am allowed to pick one only. So my best choice is the only iron I could find myself in the field. The iron I could cut and etch so many specimens of. The iron in which I could see tiny green crystals of cosmochlore, the Na-Cr silicate. The Morasko IAB-MG iron.
Morasko is a coarse octahedrite, which was first classified as IAB, then - surprisingly to me - it was reclassified to IIICD. All the time I was sure it was a misunderstanding. However it made Morasko more interesting for collectors as IIICD irons were not so common as IAB irons. Finally, to my satisfaction, Morasko was reclassified back to IAB, more recently.
There are no doubts that Morasko was a large iron shower as hundreds specimens of it were found, from tiny, completely weathered, weighing a few grams ones up to the largest one, 164 kg, found last year. There are no doubts, that Morasko was a crater forming fall, as many finds are schrapnels like those found at Meteor Crater, at the Henbury craters or at Sikhote-Alin. However, there are doubts if the craters existing at the town of Morasko were created by meteorites as they are situated on a terminal morraine and many geologists believe that they were created by glaciers.
Larger specimens of Morasko iron are full of inclusions. In smaller specimens, which are mostly available for collectors, inclusions are scarce, as the inclusions were weak parts of the Morasko meteoroid, and the falling mass of iron broke apart along inclusions. This is also the case with Canyon Diabolo, and other irons as well.

A Full Slice of Morasko from a 28kg Find, Coll. Andrzej S. Pilski

The photo above shows a full slice of Morasko, cut from a 28 kg find. Notice a large inclusion of troilite (lower right), with a rim of graphite (black), schreibersite and cohenite.
The most abundant inclusions in Morasko are cohenite inclusions, which often follow the Widmanstätten pattern. However in many specimens cohenite is lacking, and those specimens look like Campos after etching. In larger pieces there are many inclusions of graphite and troilite, rimmed with schreibersite and cohenite. Some graphite-troilite inclusions are larger than 5cm (see photo). Schreibersite also appears in the form of abundant rhabdite crystals. Silicate inclusions in Morasko are hard to find. I could see only one larger (about 8mm) inclusion, which unfortunately was destroyed during cutting. In most cases silicates appear in form of tiny grains in troilite-graphite inclusions. Recent finds of larger specimens of Morasko are currently examined by Polish researchers, and I hope we will soon hear many interesting news about the Morasko iron.

Adam C. Hupé:

My favorite iron meteorite is Sikhote Alin, an Octahedrite type iron meteorite that fell February 12th, 1947 in the Maritime Territory, Russia, specifically the variety with thumb-printing (regmaglypts). To me, Sikhote Alin represents what one would expect a meteorite to look like. I find it interesting that the larger the individual, the larger the regmaglypts. Conversely, I have observed near microscopic regmaglypts in very small individuals. The thin black magnetite coating (crust) and features like flow-lines make almost every individual Sikhote Alin a wonder to observe with or without magnification.
When I give a meteorite as a gift, it is usually a Sikhote Alin. The first meteorite that I received as a gift was a Sikhote Alin from my brother, Greg, who also caught the meteorite bug sometime after me. I feel Sikhote Alin is a great investment with many things going for it like coming from a fall, being fresh, numerous in quantity and very inexpensive. No two are alike so you can collect as many as you wish. A collector could build an impressive collection with this one fall alone as there are so many ways to put one together. Among the collectable attributes are things like Sculptural, Oriented, Shrapnel, Holed, Cratered, Zoomorphic, Letter-like or you may want the variety that can be used to remove a bottle-cap, there are no rules restricting how one can build a collection. Here are some examples:
Great example of a Sculptural Sikhote with the additional feature of being holed, a rare and desirable characteristic of ablation - click the links for more photos!

A Really Neat Sculptural Sikhote with Hole, Coll. Adam Hupé

Oriented, note the flow-lines that encircle the leading edge. This is the best example of an X-Y oriented individual that I have seen meaning that it not only stabilized during flight but rotated as well:

A Sikhote with Circular Flow-Lines, Coll. Adam Hupé

Excellent example of a crater formed when another meteoroid struck it during its brief flight through the atmosphere. Note the raised rim:

A Sikhote with an Impact Crater, Coll. Adam Hupé

Pierre-Marie Pelé:

Let me tell you the story of my favorite iron meteorite, Mont-Dieu: Late June 1994, during the Sainte-Marie-aux-Mines mineral show, Alain Carion had a stand as usual. On the last day of the Show, a young couple stopped by at Carion’s table and got a black metal piece from a plastic bag, measuring about 4 cm, relatively light and very oxydized. They explained that they got this piece from a man who had found a 40kg specimen with a metal detector, underground.
Sure to have an iron meteorite in his hands Alain Carion decided to make an analysis. Four days later, the MNHN in Paris confirmed that it was an iron meteorite. Mr. Carion was then able to meet the finder, Mr. C., next Saturday, who's house was near the Meuse river. They went to his garage where the meteorite was stored. It was very oxydized. Alain Carion bought the piece. This way, he became the owner of the 68th French meteorite.
Back to Paris, the meteorite was cleaned, photographed, weighed, measured, sliced and treated with acid to reveal its Widmanstätten pattern. The next day, Alain Carion went to the Paris Museum to show this great find to Paul Pellas. He was sure it was a multiple fall and that more masses were to be found.

Slice of the IIE Mont-Dieu Iron, Photo Courtesy Eric Twelker

Ten days later, Mr. C. called Alain Carion: “I went back to the strewnfield with a friend, we searched day and night and found more fragments, a total of 140kg. The biggest weighs 95kg. I can sell them to you for the same price as the first piece. You have a week to think about it or I'll sell to someone else.”
Wishing to be the only owner of the meteorite, Alain Carion contacted several friends to get the money. “After your last visit, we bought a better metal detector and we found again 200kg of fragments, between 5 and 15kg each; this time, we searched the whole area and drawn the ellipse.”, said Mr. C.. A total of 51 fragments were found, from 400g to 95kg. The strewnfield measures 110x20 meters.
During his summer vacation, Mr. Carion got occasionally news from Mr. C., but in September, he studied the map sent by Mr. C. and realized that the area, in a forest, is owned by French government. All fragments he owned had to be given to a museum.
Nobody knows when Mont-Dieu fell. Some believe that it fell during the 1870 war between France and Germany as the noise of the meteorite fall would have been covered by the noise of canons. But recent studies indicate that the meteorite fell many centuries ago.
But that’s not the end of the story. In August 2005, the IRSCNB (Royal Institute of Natural Sciences, Bruxelles) was contacted by a man who had found a mass of iron in its garden during excavations, several years before. After some studies, it was recognized as the 435kg main mass of Mont-Dieu, found a few kilometers from the French-Belgian border, several kilometers from the known Mont-Dieu strewnfield.
The total mass of Mont-Dieu is now 795kg, making it the biggest European meteorite fall. It's classified as an IIE iron. I'm sure that some more pieces will be found in that area.

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