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Sikhote Alin's crust

Ever since I bought my first non-shrapnel Sikhote Alin in 1993, I have been wondering what crusted pieces had looked like, when they fell in February 1947, into the snow of the Russian Taiga.

From Dr. Krinov's book "Giant meteorites" (English edition 1966), Dr. Krinov's article "Neue Untersuchungen des Niedergangs und Sammlung von Teilen des Eisenmeteoritenregens von Sichote-Alin" (Chemie de Erde; 1970) and Buchwald's "Handbook of Iron Meteorites" (1975) I learned the following:

From 1947 until 1950 four Russian Academy of Sciences expeditions explored this meteorite fall. Only in the first of these expeditions, crusted individuals were found (several months after the fall). Dr. Krinov mentioned that these individuals were collected from the forest surface soil, and were "completely or almost completely free of soil pollution and rust". Dr. Krinov described the color of the crust as "grey colored with blue-ish tinge" and "ash grey".

After an intermission of 17 years, in 1967 the expeditions were resumed. Also 1968 and 1969 had expeditions. Krinov wrote of a planned expedition for 1970. I don't know if this last one actually took place, and if there were more in the following years. Many more fusion crusted individuals were found during these 1967 and later expeditions. Krinov wrote: "the collected whole
individuals have - during their twenty year stay in the soil - been covered by a thin oxidation layer and are colored brownish" and "yet many have areas that have not been covered by oxidation and kept their original dark grey color" (I translated this from German into English).

When I bought the nice fusion crusted 230g individual shown to the right from Walter Zeitschel in 1995, he kindly informed me about its history. Walter knew Dr. Krinov personally, and wrote to me that this specimen originated from a cellar in a building belonging to a Moscow university. It was found during one of the later (1967 and later) expeditions and stored in the cellar for several decades. At first the individuals were registered and numbered, but when they became too many, they were just stored in the cellar, where they were found after 1991. Russian and American dealers bought the specimens and took them to "the west". The specimen didn't look like it does in the photograph when he got hold of it. It was still covered with soil. The piece was carefully cleaned by the use of a little (electrical) steel brush.

Note: This specimen is not part of my collection anymore.

The 216g specimen above has never been cleaned. Soil and vegetation remains can be identified by microscope. Clearly visible at (especially) the backside, is the octahedral structure of this coarsest octahedrite which has not yet been smoothened out by ablation. I expect this to be one of the specimens found during the 1967 and later Russian Academy of Sciences expeditions.

There are many qualities of "fusion crusted" individuals going around nowadays. I think the ones above belong to the better quality available. There are also tumbled or more heavily wire brushed (recently found?) specimens like the 55g one to the right.

Note: This specimen is not part of my collection anymore.

Saving the best for last, to the left my best one.
I learned this 473g specimen was acquired in Moscow by an American mineral collector, and that it originated from the Russian Academy of Sciences. It really differs from the one I got from Walter Zeitschel. It is lighter grey and doesn't look "sanded". I don't think it has been wire brushed. Could it be from the earlier expeditions? Or maybe from the 1947 expeditions. I'm afraid we will never know...

The close-up below nicely shows the grey-blue color of the specimen's crust. This crust is locally very thick and shows nice flow features and some flaking, mainly on top of Schreibersite inclusions in the center rim.

Below some microscope photographs of this 473g specimen.
click images above to enlarge

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