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

The Leoville CV3.0 Accretionary Breccia

Is it the World's Best
(internally) Oriented Chondrite?

The ploughed-up 1961 find of yet another Kansas meteorite was hardly ordinary. It turned out that the 1.6kg stone (and another stone of 6.5kg) was not the usual L6 or H5, but an ultra-rare CV3.0 accretionary breccia carbonaceous chondrite with a stage 3 shock level.

But to admirers of such things, Leoville is a glorious cosmic texture that captures both the eye and imagination taking one back in time to the very beginning of the solar system…and Maybe even beyond.

This month's installment of the Accretion Desk offers a couple views of this illusive stone, which like many rare birds, it is hard to share its true magic through mere photographs.


 
 

A 100g thin slice of the Leoville carbonaceous chondrite in the author's collection. Slices such this one are a special treat in that rarely does one have the chance to see so much cosmic type 3.0 real estate at one time.

As if the almost perfect chondrules and breccia were not enough, the abundant and large white calcium aluminum inclusions (CAIs) May contain material older than our solar system!


 

This is an excerpt from the article showing the sequence of events that May have led to the unique structure of Leoville.


 

What makes Leoville even more exciting is that its chondrules are highly elongated. And, as described by Cain, McSween & Woodword in 1986, “Foliations defined by alignment of elongated chondrules have been noted previously in chondrites, but none displays this effect as well as Leoville.”
 

 
The white puff of presolar dust floats gently in chondritic space like a nebula cloud in some distant galaxie.


 

Another graphic from the article showing the orientation of the deformed chondrules allowing for calculations defining the degree and direction of the deformation.

Note that the CAI in the upper center of the diagram is the same one as in the upper left of the above photograph.



 

According to the article, the foliations in Leoville are defined by a preferred orientation of the elongated chondrules, and are likely from in situ deformation. In other words, some event caused the normally spherical chondrules to be squished so instead of a nice circle or mild oval, Leoville's chondrules form more of an elliptical shape pointing their collective fingers toward some unknown force.

 


 

Looking like reptilian scales on some prehistoric creature, Leoville's bazarre oriented chondrules, and most importantly the CAIs, literally stretch prehistory to well beyond the early solar nebula.

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This graphic from the article shows the average shape and orientation of the deformed chondrules on the surface region of Leoville under study.


 

What makes this study of a particular slice of Leoville special to me is that the very slice used in the research now sits in my collection. The 1986 article pictures the slice exactly the same as is today which means is that all the diagrams, measurements, calculations, and conclusions pertain directly to my slice. All the calculations, that is, except the horizontal dimension which is listed in the photo caption as 6 cm, but is actually closer to 10 cm.


 

As with many of the specimens that moved through the hands of the American Meteorite Laboratory, this slice of Leoville gained a coveted AML specimen card along the way.



The Accretion Desk welcomes all comments and feedback.

accretiondesk@gmail.com