An Article In Meteorite Times Magazine
Martin Horejsi's Meteorite and Tektite Books


 

Kilbourn at $7 per gram!

“These prices are not only artificial and unscientific, but silly.”

George Merrill, head curator of the Smithsonian commenting in 1929 the on price of the Kilbourn ordinary chondrite.


Just 12 days before the Egyptian SNC named Nakhla did not turn a dog to ashes, the Kilbourn, Wisconsin meteorite did crash through a barn narrowly missing a man. What makes Kilbourn such an interesting stone meteorite to hold in one's collection is that in addition it is status as a witnessed fall, and its almost century-old age, and its sub-kilo total known weight as a single stone, and status as a "hammer," and the colorful quotes personalizing the stone, but mostly that Kilbourn's fall from the roof through the floor of a barn was well documented and published.

In this installment of the Accretion Desk, photos have been sprinkled throughout the text of a August 1, 1914 article about Kilbourn written by Oliver C. Farrington, the curator of the department of Geology at the Field Museum of Natural History in Chicago.

kilbourn face

 

The polished face of Kilbourn as represented in the author's collection. Over 70 years ago, Kilbourn was used an example of how collectors can influence the price of a meteorite simply because the stone hit something, is of low recovered weight, of historical interest, or the difficulty of obtaining it from present holders. All things considered "unscientific" or "silly" by the Smithsonian's meteorite curator.

 

The Kilbourn, Wisconsin meteorite fell at 1720 hours on June 16, 1911 in Columbia County. Kilbourn is classified as an H5 chondrite with a total recovered weight of 772 grams.

Except for the photo captions, the text is cited in Farrington (1914)

"

This meteorite fell June 16, 1911, at about 5:20 p.m., on the farm of William Gaffney, 7.5 miles northeast of Kilbourn, Wisconsin. The latitude and longitude of this locality are 43 40' N., 89 40' W.

The only observer of the fall of the meteorite was Mr. Gaffney, and to him through H. Conrad Meyer of the Foote Mineral Company the writer is chiefly indebted for an account of the fall.

Mr. Gaffney states that at the time of the fall he was in his hay field about 20 rods [1 rod = 16.5 feet translating into 330 feet or 110 meters] from his barn. While there he heard a rumbling noise similar to that produced by a heavy wagon passing over a stony road. The noise, he states, was much louder than thunder. The day was close and muggy with no breeze and no sign of a local thunderstorm. The noise lasted about three or four minutes.

kilbourn map

 

At 15 kilometers (50,000 feet) above the earth, this is the view the Kilbourn stone had as it descended toward the unsuspecting barn.

While many heard the sound of the fall, the lone witness to the impact reported that the sound stopped at the same time he entered the barn. Was it the physics of the fall, or could it be that the barn muted the sound of the falling meteorite?

While it was going on Mr. Gaffney walked towards the barn and when he entered it the sound ceased. When he had been in the barn about a minute he heard a loud report like that of a cannon and saw a small stone strike the manger about 10 feet from where he was standing, rebound, strike the stone foundation of the barn, and then bury itself to a depth of 2.5 inches in the hard-packed clay soil which formed the floor of the barn.

Mr. Gaffney picked up the stone, but found it so warm he could hold it only for a second or so. It remained warm nearly three hours. When first picked up it had a straw color on its surface, but gradually assumed a black color. Neighbors of Mr. Gaffney within a radius of three miles heard both a rumbling noise and a report when the stone struck the barn. Fishermen at Lake Mason, near Briggsville, Marquette County, Wisconsin, about five miles east of Mr. Gaffney's place, also heard a rumbling noise.

On examining the barn after the fall of the stone Mr. Gaffney found that the stone had gone through the roof, penetrated three thicknesses of shingles and a hemlock board about 1 inch thick; then, about 4 feet below this, passed through a 7/8th inch hemlock board forming the floor of a hayloft. The portion of the floor of the hayloft penetrated by the meteorite was submitted to the writer for examination, and a photograph of the same is shown in Plate VI.

kilbourn hole

 

This image from the Farrington article shows the penetration hole in the Hemlock floor of the hay-loft of the barn. The hole is roughly 10cm by 5cm, and about the size of the actual meteorite.

Having a hardness of about one-third of that as Maple, Hemlock has the oxymoronic distinction of being the hardest of the softwoods. It's list of undesirable qualities as a construction wood seems rather long, and its Janka hardness of 500 ranks it near the bottom of wood species used in flooring. For the meteorite, it was a good thing the wood was not Brazilian Walnut, a species with a Janka hardness of 3684!

The hole said to have been made by the meteorite is about 4 inches long by 2 inches wide, and is about the size and shape that such a projectile would have made. The shape of the hole indicates that the meteorite was moving in the direction of its longest axis and not broadside when it penetrated the board. It does not seem to be possible to determine positively from the shape of the opening which end of the meteorite was in front, although the indications are that it was the pointed end.

The meteorite fits the opening in the board a little better in this position, yet the opposite end of the meteorite shows abrasion and removal of the crust in several places, in a manner that might have been caused by the striking of this end against boards. The penetrated board has the brittleness peculiar to hemlock and hence might offer less resistance to a falling body than some other kinds of wood.The barn stands in a north and south direction with the roof sloping east and west. The stone fell upon the east slope of the roof and appears to have come from a direction a little south of east.

kilbourn face

 

For having such a low TKW, it is somewhat surprising that Kilbourn is very well distributed in major collections both in number and in specimen size. According to the Catalogue of Meteorites, the breakdown of material is as follows:

87g Vienna Museum

86g GSC, Canada

85g ANH, Philadelphia

70g Field Museum, Chicago

70g Harvard University

50g AMNH, New York City

41g Arizona State University

*my 28g slice

19g Vatican

1g Max Planck

1g BMNH, London

And a further inspection into the Kilbourn material at the Field Museum in Chicago revealed the following:

  • ME 795 Microscopic slides; thins section with cover.
  • ME 797 Full sized sawed section with crust. 61.60g
  • ME 1991 Fragments from interior. 7.70g
  • ME 1992 Portion of a barn floor through which Kilbourn fell

 

The stone is comparable in size and shape to a man's fist. Its appearance on several different sides is shown in Plates V and VI. It weighed a little less than 2 pounds, the exact weight being 27.5 ounces, or 772 grams. The specific gravity of the stone as a whole was 3.43. Its length was 4.5 inches (11.5 cm.), width 3 inches (8 cm.) and height 2.5 inches (6 cm.).

One relatively broad, though somewhat rounded, surface forms a base from which the other surfaces rise more or less irregularly. These irregular surfaces nearly all show pitting such as usually characterizes meteorites, but the pits are especially numerous over the concave surfaces. The pits are shallow, irregular in outline, and have an average diameter of about 1/4 inch (6 mm.).

More unusual than the pitted surfaces are two nearly plane surfaces each of about one square inch (2.5 sq. cm.) in area which come together with a third slightly pitted surface to form a rather steep pyramid at one end of the stone. This aspect of the stone is shown in Plate VI. This end of the stone resembles a tool shaped for piercing or boring.

On the edges produced by the joining of these three planes there is a marked smoothing of the crust, its surface being compact and glossy. This smoothing extended on one edge for about 4 inches (10 cm.), on the other two about one inch (2.5 cm.). It may have been due to the friction of passing through the boards of the roof and loft if this portion of the meteorite was in front, but whether such was really the case the writer is unable to state.

kilbourn complete

 

The 772g complete individual of Kilbourn as pictured in Merrill & Foshag's 1929 book titled Minerals from Earth and Sky.

Merrill wrote on page 52 of the book:

"The small meteorite which fell in Kilbourn, Wisconsin, in 1911, and passed through a board in the roof of a barn, sold as high as seven dollars a gram, largely on this account, as it was a stone of a common chondritic type.

Obviously a meteorite has no actual value and these prices are not only wholly artificial and unscientific, but silly.

It should be added that this condition is due largely to the mere collector rather than to the serious student. Ambitious heads of departments in our public museums are, however, by no means blameless."

 

The meteorite when received was nearly covered by a black crust. Where the crust was lacking the lack was evidently due to abrasion from striking the barn and to the removal of portions by the finder for examination. The crust was dull, rough, thin, and adhered firmly to the interior. Under the lens its surface is seen to be covered by a network of little ridges of matter which had been formed by flowing when in a fused state.No definite drift of these ridges could be discerned.

While much of the meteorite is covered with crust of this character over some surfaces the crust takes the form of little, dark, glassy spherules thickly scattered over the gray surface of the interior. The continuous crust is more or less penetrated by meandering cracks which give the surface a crackled appearance.

kilbourn crust

 

As I've said before, crust is always a good thing, and might be the only thing given the number of questionable specimens where a small crustless slice of a hot desert stone is passed off as a rare witnessed fall.

In the case of my slice of Kilbourn, crust flows on three of the four sides, and offers brief but captured glimpses of the contours and curves of this beautiful stone.

 

While the general color of the crust is black, at the bottom of many of the pits and in the shelter of overhanging edges it has a reddish color, indicating a higher oxidation of iron at these points. The color of the interior of the stone is gray, more or less tinged with brown from iron oxide. The texture is compact and so firmly coherent that it can be broken only with difficulty.

Surfaces take a good polish. There is an abundant admixture of metallic grains in the stone. These are of small size and uniformly distributed. As seen on a polished surface they are very irregular in outline but at times elongated. They rarely exceed 0.5 mm. in diameter. Nearly all consist of nickel-iron but a few show by their yellow color that they are troilite. The siliceous ingredients of the stone are largely in the form of chondri, plainly distinguishable on a polished surface by their circular outlines.

kilbourn crust

 

Another view of the rich black crust. According to the account of the fall,

"Mr. Gaffney picked up the stone, but found it so warm he could hold it only for a second or so.

It remained warm nearly three hours. When first picked up it had a straw color on its surface, but gradually assumed a black color."

Imagine the scenarios that could cause this observation:

1) The stone was actually covered in frost and Mr. Gaffney's imagination and nerve confusion caused to assume the stone was hot.

2) While the electrification of the midwest was underway, I doubt the barn had any electric lights. So possible the crust was quite black, but also more shiny than after frequent handling. As shiny black crust reflects light better, in the barn it may have appeared much lighter in color.

3) The fall occurred in the late spring at about five in the afternoon. Imagine the position of the sun at the moment of the fall, then again three hours later after the stone 'cooled.' A lower angle evening sun in the barn could also explain the color change.

Of course, the stone could just have been very hot and straw colored before slowly turning black as it cooled.

 

Some of the chondri are black in color, others are dark gray and others light gray. The largest chondrus noted has a diameter of 2 mm. ; the average are about half that size. The chondri as a rule break with the stone but occasionally separate out, especially on polished surfaces. The megascopic characters seem to place the stone in Brezina's class of spherulitic chondrites. Under the microscope, chondri are seen to largely characterize the structure of the meteorite though their quantity is not as great as in some meteorites.

kilbourn matrix

 

A close-up of the polished matrix of Kilbourn offers ample metal engulfed a greying matrix sprinkled with possible shock veins and hints of brecciation. All and all, 1911 was a good year for meteorites.

The ground mass is for the most part well crystallized, the crystals being large and with definite outlines. The prevailing minerals both of the chondri and ground mass are chrysolite and enstatite, chrysolite being the more abundant of the two. The chondri present the usual porphyritic, radiated and lamellar forms. Of especial note among the lamellar forms is one in which the lamellae run in three directions at angles of 60.

The three series of lamellae have different extinction angles and the border zone extinguishes in unison with one set of the lamellae. The crust is thin for a meteorite so coarse in structure and nowhere in the sections examined by the writer shows an absorption zone. The outer or fusion zone is very nearly one-tenth of the thickness of the impregnation zone. The thickness of the two zones combined approximates closely to 0.4 mm. The impregnation of fused matter from the surface due to the formation of crust affects the ground mass but does not penetrate the chondri.

"


As with all my meteorites, Kilbourn is one of my favorites. Looking back on its fall 97 years ago, and considering the selling price, I have to agree that $7 per gram is silly. But not as silly as those collections that missed out on adding this special ordinary chondrite to their cabinet.

The author would like to personally thank Frank Cressy for his research into the Kilbourn fall unearthing the historic references for me.


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