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MISSING: 9.04 kilogram Sikhote-Alin shrapnel individual   More Info

2021 Fall Date Project

The MPOD Caretakers want to present meteorite falls on their fall dates. For example, Sikhote Aline on 12 February.

This Project will not dip into the MPOD archives so the Caretakers will appreciate anything you can contribute.

To reserve a date just let us know. Thank you in advance :)

Fall Calendar           Dates reserved so far


San Juan de Allende   contributed by Steve Brittenham, IMCA 2184   MetBul Link

Roll Overs:     #1   #2   #3   #4   #5   #6   #7   #8   #9    

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View all entries for   Meteorite (2)   Contributor (83)

Copyright (c) Steve Brittenham.

TKW 200 grams. Fall not observed. Found August 1995, Chihuahua, Mexico.


Steve writes:
Like Salaices (see MPOD 11/6/2020), today’s chondrite was also found in the Allende strewn field. Because Ruben Jurado’s large farm overlapped it, he trained his laborers to identify and collect meteorites. When they found a sufficient number of stones, Ruben would come to the next U.S. trade show to sell them.

Ruben was kidnapped and killed in 1996, not long after having delivered a 6 kg bag of Allende CV3s to Edwin Thompson. Besides the carbonaceous chondrites, within that bag were two partially-crusted ordinary chondrite meteorites. The largest weighed approximately 200 grams, and a 113.4 gram piece was cut from it and sent to the University of New Mexico for subsequent classification. Photo 1 shows its mainly fusion-crusted side; Photo 2 displays a partially crusted one.

[At 102.7 grams, the smaller second stone was sent uncut to UNM at the same time – tomorrow’s MPOD will describe it.]

Dr. Adrian Brearley initially thought it might be either a highly unequilibrated H3 or an LL3 (Photo 3 shows notes written inside the lid of its box). But before it could be actually classified, Dr. Brearley was given a tenured position in the chemistry department, and it was set aside and subsequently forgotten for more than two decades. It was rediscovered earlier this year and returned to Edwin, but in the intervening period, Edwin had sent some of the remaining material to Portland’s Cascadia Meteorite Labs (CML), where metal and oxygen analyses by Dr. Alex Ruzicka subsequently confirmed it to be a less interesting L3. Still, it’s quite rich in chondrules, as seen on the cut surface in Photo 4, with a closer view in Photo 5.

I had previously purchased Edwin’s remaining 18.7 gram piece of this first stone two years prior to its 2018 MetBul listing. Nicknamed Allende "F" because of a handful of non-carbonaceous chondrite meteorites found in the Allende strewn field before it, the actual MetBul listing was delayed for over a year while awaiting an exact location of its find for a more formal name. Since San Juan de Allende was the closest municipality to Ruben’s farm, it became the namesake for this meteorite. Then, when the 113.7 gram main mass was subsequently returned to Edwin, I acquired it too.

Just recently, Dr. Melinda Hutson was kind enough to lend me the uncovered circular thin section plug used for CML’s classification work. My scanning system is not set up for circular plugs, and my optics are optimized for thin sections with cover slips, so the results weren’t as sharp as some of my other gigapixel thin section images. Still, the results show a variety of chondrules found within this meteorite. Links to the xpol and white light thin section images on Gigapan are can be found here (Photo 9 shows both side-by-side):

San Juan de Allende L3 Chondrite Thin Section in xpol

San Juan de Allende L3 Chondrite Thin Section in white light

For those new to Gigapan, click on the diagonal arrows at the right of the image to enter full screen mode, then use your mouse to pan around, and its scroll wheel to zoom in and out.
Click to view larger photos

Photo 1

Photo 2

Photo 3

Photo 4

Photo 5

Photo 6

Photo 7

Photo 8

Photo 9

Found at the arrow (green or red) on the map below


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San Juan de Allende *
Steve Brittenham

This Month

Mitch Noda
 12/6/2021 10:49:52 AM
Nice write-up, Steve. Tragic about what happened to Ruben.
Scott McGregor
 12/6/2021 10:24:01 AM
Thanks, Steve. The story behind the specimens really makes them special...
 12/6/2021 2:19:27 AM
great story, steve, thanks for sharing.

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