Serving The Meteorite Community Since 2002

Almost the Whole Story of a Big Chondrite

I don’t add very many meteorites to my collection anymore. Maybe five or six meteorites a year. Of that number, a couple of meteorites are stones I partner with Jason Phillips to buy and get classified. Just as the virus was getting going in March 2020, we arranged to purchase a 15kg stone. It would be the largest piece in my collection once cut in half. I have stones in the 2-3 kg range but, this would be a size jump for the collection. Soon as we made the arrangements on the stone the world shut down; nothing was getting shipped. I tried not to think about the stone that was stuck far away. Two or three months passed and like an itch wanting to be scratched, I would think about the stone occasionally and fight the impulse to call and ask “where is the stone!” Eventually, the stone did arrive. We sent it off for cutting because it was too large to fit any of my saws.

Meteorites are always just a little mysterious. They can seem sound and strong only to reveal hidden cracks. And that was certainly the case with this stone. Jason and I had wanted to get one slice of the stone to go along with our halves. But those slices turned into a single major piece for each of us and a bunch of smaller pieces that fell apart on cracks. It would have been the same if I had modified a saw and figured out how to get it cut at my lab. But who doesn’t like a jigsaw puzzle? Many of the pieces fit together very tightly, which offered us the option of supergluing them together. I don’t do this ever. But this time, it seemed somehow ok since we were keeping the slices ourselves. I had to grind and polish the pieces since they were rough from the saw anyway. Grinding off the little bit of glue was not much extra work. So Jason sent his slice pieces to me to finish for him. I did the work immediately and had his slice in the mail back to him. As of this writing, his slice is still lost in the mail tragically. It is in his local post office building somewhere, but they can not find it.

I had the half stone to figure out. It had to be ground and polished or maybe just ground smooth and not polished. But it could not stay as it was rough on the cut face. I would have to put it on a slab and grind it like a telescope mirror with loose abrasive grit until it was nice and smooth. I could put it in the 28-inch vibrating lap, but I have never done meteorites with that machine. I dislike the idea of them lying in a water slurry for days and days on their face.

There was a smaller mass of the stone weighing 429.5 grams, and since my “half” was lighter I had gotten it that stone the split of the material. Many smaller pieces were also generated in the cutting. I wanted to make thin sections from some of them.

Pictured here is the outside of the 429.5 grams stone. Easily seen are the bumps of the chondrules with which the meteorite is rich.

I suppose I should start talking about the stone itself. First, it has very little metal. Second, it has wall to wall chondrules. The chondrules are not smashed against each other. There is some groundmass between them, but they are prolific, thousands visible across the surface of the half stone. Third, the chondrules are well defined. With the naked eye, they appear to have crisp edges. We were certainly thinking of type 3 when we bought the stone using the pictures supplied by the owner. We desired to have the stone classified to the subtype this time for the fun of it.

The repaired and polished full slice of the meteorite shows the small amount of metal it contains. Some weathered spots of troilite also can be seen in this image.

There was some fresh fusion crust on one area of the stone with great flight marks. Both Jason and I agreed the fair thing was to have the stone cut so we could both get some of the nice fusion crust on our half. As big as this stone is, it’s clear from the large broken surfaces there was much more originally. From what I have seen in my life, meteorites break pretty easily when they smack into the ground. A 100% fusion crusted stone is seen less often than stones with a chipped spot in the fusion crust. Our 15kg stone had whole sides missing.

The small patch of fusion crust that was on the 429.5 gram stone is shown above. It is this writer’s opinion that this small stone is not an individual but a broken off fragment of a very large stone of which we only have a 15kg large mass.

So a supply of this material is still in the desert or already found waiting for someone else to buy. Will they get their piece classified too? Well, that has been a problem over the last three decades. Some number (and I think it is significant) of the meteorites listed in the Meteorite Bulletin Database are redundant. Some of the database entries are multiple times redundant. Al Haggounia 001 for instance, has nearly twenty different numbers and names. And for years it had several different classifications. A situation I am happy to say, finally resolved with it no longer being called an Aubrite.

I do not ever intend to sell this big half stone. But selling is the motivation many times for getting a number and making your stone official. Classified meteorites generally sell for more money. Also, you have at least the feeling you are somehow more in control of the distribution and the information about the meteorite. But the reality is not quite that good. Some meteorites are so distinctive that they get sold as additional masses of a stone another dealer or collector has gotten classified just by their appearance. Not a terribly troublesome thing if the additional masses came from exactly the same location. More stones are often found with subsequent hunting. Accusations of visual pairing and number stealing have happened occasionally over the years. But, the idea of getting every stone classified from every location is absurd. There will never be available laboratory resources for that. There is also the problem of intensive hunting at a single spot which recovers more than just the one fall. Other older, and different falls may be recovered and often mixed together causing confusion and misidentification. There is no deliberate deception involved in this case. In sorting and working with thousands of NWA869 stones over the last two decades I have found a few dozen stones that are mixed in which are not NWA869. They were likely found in the same location for they are the same among themselves. They are not brecciated and have a different color when cut. But from the outside they were similar enough to be thrown into the one box in the field.

If the stones from the various falls at the same location are also the same type then the problem of which is which can almost not be unraveled. The Franconia area of Arizona is such a situation. Two nearly identical ordinary chondrites are found in the same area. It is a desert so weathering changes occur over long periods of time. Visually the stones are nearly the same. Only laboratory testing for terrestrial age can definitively determine which fall name is correct for a stone found in the overlap area of that dense collection zone. A zone that includes several other falls of various types.

I just usually want to know for sure what my nice stone is. That requires sending it to someone at a laboratory. I doubt very much that this large stone fell alone. There is likely much more of it and it may already be classified. Perhaps classified several times. The equipment is sophisticated today and the procedures far more uniform and accepted from lab to lab. One might expect that the stone would receive the same classification every time it was submitted to a lab. But that too is not the case. Stones just do not always come that uniformally composed. They are often borderline between two types.

Sometimes as we desire with this stone they are classified to the fractional type stage. A meteorite could be analyzed and found to be a type 3 at one lab doing a basic classification. It could be classified as a type 3.2 at another lab and maybe a type 3.2-3.4 at a third lab. These could be all the same meteorite. The classifications make it appear that they are different. Find and or purchase dates might widely vary. One-piece might have been bought in 2010 from a box at the Tucson Gem and Mineral Show and classified immediately while another piece might wait ten years in the same box to be bought in 2020 and classified even later. This is why knowing the exact location and the circumstances of the find are so important. Truthfully providing that information is the best way to reunite stones with closely similar classifications as being members of the same fall. But for marketing reasons, locations are often missing for the stones and it becomes a “bought at Tucson” or it came from “insert country name here.” Or as was the case in the late 1990’s “I found it but I am not going to tell you where except by code. I will release a key for decrypting the location in the future.” Which may never happened and the exact find location of hundreds of meteorites will remain “secret” to us who bought them expecting to know someday where they came from. The result of all this is resources are expended on classifying the same material over and over. I don’t think there is an answer to this. I want my own number and so do others. I do not know if anyone else has classified a piece of this big meteorite so I must get it done. I don’t want my number being used for some other stone. I do not want to just use someone else’s number for a stone that looks very similar. I don’t want a supplier in some other country selling me a stone and then waiting until I get a number for it so he can then sell the balance of the material found at the same spot as a classified stone without going to the expense himself of getting the classification. These irritating things do happen often enough. This can be a big money thing when it is a lunar or martian meteorite where the classification work costs many hundreds of dollars to get done. But I think we all know that there are not hundreds of lunar meteorites that all look the same. We know there are a few with a lot of different numbers from redundant classifying. There is a positive side occasionally. Some new and different lunar meteorites have been discovered because of the testing of so many stones. They look nearly identical but some have turned out to be different and this is a fantastic happenstance. Just as a side note a stone can be classified by two different labs because the samples sent were different. It has happened with eucrite/howardite stones at least once I know of. They were classified as each of those meteorite types by labs because one sample of the stone had slightly more of one mineral than the other and was called Howardite while the sample at the other lab was slightly more eucritic and got Eucrite. I don’t want to get even started on the problems of sending only one lithology of a brecciated stone with say three lithologies. There is often the desire to send the necessary small sample but sometimes sending too little can bite you on the backside later.

So a fragment of our stone is sitting in a lab waiting for a thin section to be made. As of this writing, it has been about eleven weeks since the specimen was sent to the thin section maker. I am about a month away from the publication date as I write this, and hope is failing that I will have results back from the classifier about this stone by the time this issue of the magazine is released. So I took three of the small fragments and went to my lab. I used a couple of them as they were and sliced two into 1.5 mm slices just basically butterflied them. I ground and polished one side of each and mounted them on glass slides. I ground and polished them into five finished thin sections very close to 30 microns. They need a smidge more off. But they work ok for now until I have time to get back to them. I enjoy doing this with the meteorites I send off for classification. It makes a nice addition to my collection having thin sections of the meteorites that I solely own.

Is this stone a type three? I don’t know, I think it could be. I hope it will be an LL3 since it has so little metal and the chondrules vary in size so much. Seems like those are two easy visual features LL3 often have. I will include a few extreme close up images here for your enjoyment. They were taken from my thin sections. I must continue waiting forever for the thin section for the classifier to be made.

I am going to have to make some kind of a stand to display the half stone. I think one made of iron is the way to go. But where to put it. I am about out of room in my office. I may have to put some items away in order to make room. As I write this I don’t know if the stand will be made before the issue is released. If it is I guess I will have to do a rewrite and insert an image. That is one of the interesting aspects of writing for a magazine that comes out often. There is the need to write early to make the deadline, but regular work must be done along the way at its own pace. They do not always dovetail together in the proper order to give the answers needed for the publication. What I do know is that this stone can not sit on the pull-out shelf of my antique rolltop desk for very much longer. The need to create the stand is moving up to the top of the list of chores fast. But first, I need to get it to the lab and grind the face and decide if it will be polished before I can weld up a stand and base. With the holidays over my schedule is a little more relaxed and I can figure out how to squeeze few things in. I have about a three weeks of eight hour days just in cleaning, cutting, lapping and polishing of normal meteorite work. So the smoothing and making of a stand for this stone might be a month off.

The 429.5 grams piece may or may not be a second mass. My intuition says it is a broken-off piece of the large mass that we could not fit to anywhere on our big piece. It has dirt on the surface but the fusion crust is only on one face so could easily be a piece broken off the big mass. If it had fusion crust anywhere else it would help to prove that it was an individual. It had a ground off area on one side where it was poorly smoothed to offer a look at the chondrules. I finished the work in that area by grinding it properly and polishing it. Here is an image of that surface.

Occasionally a chondrule on a cut and polished face will show its texture in a striking manner. That happened with the large dark chondrule in the upper right of the image above. I have blown up that chondrule in the image below. It appears to be a nice polysomatic chondrule.

Sometime in the future I will get the word that this stone is official and it will have a number. By then I might have another off to some laboratory working its way through to full recognition. This has become a new fun way to enjoy meteorites as I slow down my buying to just a few a year.

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