Witnessed Fall: Borkut, Ukraine

An October 1852 Witnessed Fall: Borkut, Ukraine

The Borkut Meateorite:

More Chondrite, Less Fat

Borkut meteorite

Early comparisons of the Borkut meteorite to others of the time led some scientists to conclude that Borkut had a higher chondrite to matrix ratio. 

This uncut face of Borkut shows the chondrule-rich landscape, yet not unlike a conglomerate sedimentary rock found here on earth. How about that big pebble!

According to the few reports of the fall of the Borkut meteorite, at around 3:00 in the afternoon, a single stone fell from the sky burying itself about two feet into the ground and described as still warm when recovered.

It weighed a total of 12 Vienna pounds, with the largest of the broken pieces toping the scales of the day at seven Vienna pounds and 6 1/4 loths. The Catalogue of Meteorites lists the TKW of Borkut as 7kg or 15 pounds 6.4 ounces for us Americans.


Borkut meteorite

The blade of a saw turns spheres into circles. 

Spend some time staring at this cut face. The longer you look, the more chondrules and features you will see. Notice the arc of broken white chondrule in the lower left.

Or the large radial olivine-colored chondrule in the lower right.

Or the white silicate armor surrounding the inclusion in the upper right.

The Catalogue of Meteorites (2000) lists Borkut as an single 7kg stone L5 chondrite that fell on October 13, 1852. The place of fall is Zakarpatska Province, Ukraine. However the 1923 edition of the Catalogue by George Prior lists the location of the Borkut fall as Marmoros, Ruthenia, Czechoslovakia.

And if that discrepancy is not enough, there was a brief note in Meteoritics & Planetary Science (Vol. 36, No. 9, Supplement , 2001) that lists Borkut as from Hungary citing the 1985 Catalogue of Meteorites as the reference.


Borkut meteorite


Landing on a world that was enlightened about meteorites barely half a century earlier, Borkut was an important sample for its day. Early studies of Borkut by Tschermak and others noted the richness of the chondrules secured in a somewhat limited matrix.

 

For me, it is pieces such as this Borkut that show a the complexity of chondrule/matrix interaction furthering the confusion about the initial formation of the visible geology of the early solar system.

Borkut meteorite

The microphotographs above and below were taken by Gustav Tschermak von Seysenegg and published in 1885 in work titled Die mikroskopische Beschaffenheit der Meteoriten, later republished in English in a tome titled The Microscopic Properties of Meteorites, Vol. 4, No. 6 (Smithsonian Contributions to Astrophysics, Washington, D.C., 1964). 

Tschermak’s words, translated by Translation by J.A. Wood and E.M. Wood are as follows:

Part of a porphyritic chondrule in the chondrite Borkut; olivine crystals in a brown glass matrix. Much of this glass is enclosed by the olivine crystals. The upper crystal seems to have been sectioned parallel to {100} so that the sharp edge (021) ∠ (0?21) is presented.

The large glass inclusion in its center seems to fill a negative crystal. Other glass inclusions are also visible and, although incomplete, suggest a lamellar structure. Below is a larger crystal, bounded by distinct crystal faces.

It is penetrated by several parallel tabular glass inclusions, which give it a chambered character. To the left is an olivine crystal with very few inclusions.


Borkut meteorite

A double chondrule in the chondrite Borkut. The smaller part is a monosomatic compartmented olivine chondrule with a pale transparent shell; translucent material fills the space between olivine plates. 

The large chondrule, which partly encloses the small one, is of the same character; both go to extinction simultaneously. Borkut is fragile and tends to disintegrate during sectioning, so that the double chondrule is partially separated from its original matrix.

(Again, translation by J.A. Wood and E.M. Wood)


Borkut meteorite

With the Tom Phillips faux antique scale cube for comparison, it is easy to see the large size of that odd rock fragment just to the right of the broken face which is just to the right of the cube. 

The plethora of chondrules has led one observer to compare the spheres to grapes. Although Borkut did not fall in a vineyard like other meteorites, I cannot get that simile out of my mind when I look at the grapes, err, I mean chondrules in Borkut.


Borkut meteorite

Is this what crust looks like on Borkut? It’s hard to tell because the surface of Borkut is unlike most other meteorites. 

Normally the matrix holding the chondrules makes a nice melted surface with chondrules bubbling up through the velvety sheen.

However Borkut, being mostly chondrules, reacted to the atmosphere’s attack differently. At least that is my scenario when assuming that the exterior of Borkut pictured above represents a sample of fusion crust.


Borkut meteorite card

About six years ago, the wonderful sample of Brokut made its way from the Jim Schwade collection into mine. 

About 11 years before that, the specimen moved from the J. Schmutzler collection into Jim’s.


Oddly, the collection history of my Borkut piece is good knowledge to have as a collector of historic stones. What’s odd you might ask? Simply the fact that of Borkut’s 158 years on this planet thus far, I can only account for about 10% of its time on earth. So Borkut, where have you been hiding?

 

Until next time….


The Accretion Desk welcomes all comments and feedback. accretiondesk@gmail.com


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About the Author

Martin Horejsi
Dr. Martin Horejsi is a Professor of Instructional Technology and Science Education at The University of Montana. A long-time meteorite collector and writer, before publishing his column The Accretion Desk in The Meteorite Times, he contributed often and wrote the column From The Strewnfields in Meteorite Magazine. Horejsi is currently a monthly columnist in The Science Teacher, a journal by the National Science Teachers Association. Horejsi specializes in the collection and study of historic witnessed fall meteorites with the older, smaller, and rarer the better. Although his meteorite collection once numbered over a thousand pieces with near that many different locations, several large trades and sales have streamlined the collection to about 250 locations with all but 10 being important witnessed falls. Many of the significant specimens in Horejsi's collection are historic witnessed falls that once occupied prominence in the meteorite collections of Robert A. Haag, James Schwade, and Michael Farmer. Other important specimens were acquired through institutional trades including those from The Smithsonian Institution, Arizona State University, and other universities.
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