An Article In Meteorite Times Magazine
by Jim Tobin

Whatís Under the Surface

The remainder of February after Tucson is always a quiet time. I have meteorites to catalogue, weigh and paint numbers on. I usually have some unclassified meteorites to cut or window. And that was the case this year as well. I bought just under a kilogram of very nice black fusion crusted fresh looking stones. Several of the small stones were almost perfectly fusion crusted and I am not going to do anything with them other than put a catalogue number on them. But, some of the larger ones have spots that lend themselves to grinding a window. At some time in the future I will probably grind or cut them. Right now I am still too in love with the way they look to do anything..

However, I have some I got a while back that are not nicely crusted or pretty to look at. These are the larger pieces from a one kilo lot that I bought off Ebay. I had gotten the particular lot for two pieces I could see in the auction photo. One was almost four hundred grams and quite nice with some old fusion crust still on it. Another piece was smaller but also a nice almost complete stone. The rest of the lot was fragments of much more weathered meteorite. Two pieces of this poorer material were nice sized. There was nothing keeping me from putting these weathered pieces on the saw or lap and finding out what they looked like inside.

It is often a surprise when you grind a large window on an unclassified piece of space rock. I sometimes think this will just be a rusted out stone with big pits where the nickel iron grains once were. Or I may think another one is different and could be interesting when cut. Well, I had no expectations of finding anything very interesting with these two pieces and again got surprised. They were both really weathered in appearance. Yet when cut the matrix was still quite light in color and the metal was present with no visible rusted out holes. There is no doubt that they have been around a long time. One is cracking apart and is covered with caliche. The other is an ugly fragment that has broken off larger masses repeated to become the angular shard it is today.

126.3 gram fragment of unclassified chondrite with little metal.

216.8 gram fragment of unclassified chondrite with abundant metal

The cut surfaces showed easily visible chondrules in both. One has small chondrules of uniform size. The other has a mixture of chondrule sizes. One 2 mm radial pyroxene chondrule is very noticeable. From just the hand lens observations the chondrules are in good but not great condition and I am guessing both are petrological stage 4 - 5 ordinary chondrites. The dense amount of small metal grains leads me to conclude one is an H. Whereas, the other has much less metal, but a scattered dusting none the less. So not an LL but an L. Of course now days most of these visual or weight of metal determinations have been replaced by sophisticated laboratory tests with microprobes and thin section analysis. Still I have been right more then wrong with this over the years. They are just weathered pieces of meteorite not really worthy of expensive testing at this point in time. I can always make myself a thin section in a couple hours and take a look at what is really going on with them if I really want to know someday.

They are certainly weathering grade 3 or 4. But, it is interesting how some meteorites get very dark and the metal is completely gone. When this happens it is hard to see anything in the slice. Others stay relatively light in color so that much can still be seen with a hand lens. I had a discussion in Tucson about how long these stones have been around and it was remarkable to hear that at least one scientist thinks that we are collecting stones that are hundreds of thousands of years old. We have been hearing figures like 40 -50,000 years for the oldest ones. The ones that are fresher looking it was mentioned may likewise be much older. I had been thinking hundreds of years to a couple thousand years at the most for some of my fresh looking stones. But, was told they may be more like five thousand year residents of our world. I think that this will be one of the interesting side notes of the meteorite abundance we have enjoyed the last decade. Issues such as rates of falls for various types and the terrestrial age of meteorites will be greatly refined after this vast quantity of material has been throughly studied.

I have no explanation other than the obvious that some were subjected to much less water as a reason they are fresh looking inside. It is always nice to find that condition when you cut them however. You think you have a rusted out piece of crap and find that you have an ugly but better preserved meteorite actually.

I was thinking that these two pieces would probably be candidates for cabbing into jewelry stones or something like that in the future. Now I donít know if I can do that with them. I have mixed feeling about the whole idea of grinding up meteorites for jewelry. Besides the tremendous cutting loss in the material itself; there is the loss of the stone for future use in some other way. But, to be honest, some of the material is just really bad and will never be used for anything. These two fragments just happened to turn out better than I had thought. I have some material that is so bad making jewelry out of it is maybe the only way to preserve it from being discarded in the future after I am gone. It just looks like old rock and has no metal left and is flakey and crumbly. I donít know that making something out of this material might not be a good thing. Especially if it helped to bring more notice of meteorites to the general public. And unique jewelry is something that has a way of getting noticed.

On the down side however is something else I was told in Tucson. One supplier of cabbed stones was looking for a source of meteorites large enough to supply the manufacture of 10,000 cabs a month. That is a huge amount of meteorite when you consider there is probably 70% loss in making round topped stones for jewelry. They were not looking for rusted out crap either, but good quality OC material.

Still, there is always a fad of some kind going on. Pet Rocks or space rocks, with the supply from the desert dwindling we may see an end to this trendy use of meteorites. We may have to get back to collecting the way it used to be. I went through my database recently and was surprised to find that even in this meteorite rush I had maintained mostly my buying of falls not finds. I have added a lot of weight to my meteorite holdings. And at little cost in dollars, during the rush, but the collection itself is still made up of only named and catalogued meteorites. It has not been affected very much by the meteorites from the north west of Africa. Twenty years ago we waited patently for a dealer to do a museum trade and cut some material that we had on our want list. Or we obtained some of a new fall once or twice a year if lucky. We built a collection very slowly. I have enjoyed the last few years when it has been a faster pace. But am enjoying the return to historic and important falls that I see being presented again in dealer rooms at the shows. I guess I just like old stuff more. And if my NWA meteorites turn out to be hundreds of thousands of years old I will appreciate them more too I guess.