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NWA and clasification validity.


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Hi from a very much novice enthusiast!

I am a physics teacher from Croatia and have always been interested in astronomy and related subjects. I have loved the idea of one day owning an actual meteorite but I was so convinced that they must be so far outside of my price range that I actually never checked the actual e-bay listings. Well, a few days ago I did and am now a proud owner of a (tiny) slices of Muonionalusta, a NWA CV3 and CM2, and a tiny crusted Chelyabinsk. They are still en route and I can't wait. Considering I am on a limited budget and am perfectly fine collecting 300mg slices (I also love macro photography) I have decided to limit all my purchases to tiny slices. The upside is that I can possibly afford even an exotics such as Lunars and Martians, or can I?

While doing my research on the availability and the prices, I have downloaded and parsed the Meteoritical Bulletin Database and did some crude statistical analysis that made me question the validity of NWA meteorites classifications. Even though the number of NWA found per year has not significantly changed from about year 2000., the percentage of the finds that are either classified as Lunar or Martian has skyrocketed in the years 2013 and later (from ~3/year to 30/year). When the NWA meteorites are excluded, no such global trend exists. I see no reason why finding a Lunar or a Martian meteorite would suddenly become easier in a desert when compared to a common chondrite. There is even a relative spike in CM2 finds in the last two years. Does that mean that most (possibly up to 90%) of NWA high value meteorites are miss-classified or is there another explanation? As much as I would like to be able to show off a tiny rock from the Moon or Mars to my students at school, I would like to think I have bought the real thing. Any thoughts?

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I'm not an expert but I do know that as far as Lunar meteorites go they look nothing like other more common meteorites, they look so much like earth rocks that I think most meteorites hunters dismiss them as a earth rock since they are or were very uncommon finds for the average meteorite hunters, that may have changed due to hunters educating themselves as to what to look for.

As far as to the question concerning Martians meteorites I know nothing about them so I can't give a possible explanation.

That being said if you get a Lunar that has the proper certification I would say you should be safe and have a genuine Lunar.

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So, buying from a reputable IMCA member an apparently university tested and classified Lunar meteorite should be fine, even if it is a relatively recent NWA find? My worry is that it's maybe become possible to decently fake the fusion crust and that the rock is then classified as Lunar simply based on the similarity to earth rocks, taking that it's a meteorite for granted. Hopefully these tests are a bit more thorough and reliable.

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You will have to wait for others who are more knowledgeable than I to answer your questions on how they test to have a meteorite certified, but from the little I have read about the testing it's seems to be a very exact and professionally done process, as far as faking fusion crust I doubt it can be done well enough if at all, especially so to fool the scientists who do the actual certification testing.

That being said I guess someone even a I.M.C.A. "member" could fake a certification certificate so it would be up to you to follow up on the documentation to see if it's is authentic by contacting who certified the specimen.

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It's not that planetary meteorites have become any easier to find, it's that labs more and more do not want to analyze "ordinary" chondrites; they want to see the unusual stuff, so you see many more HED and planetary rocks being classified.

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Dsvilko,

Labs everywhere are being inundated with meteorites for classification. Therefore, most of them are turning down common L and H stoneys and only classifying and publishing Martians, Lunars and other unique and rare classifications. NWAs are commonplace and not worth the time for most labs. The exception is if it is a new fall, or a new same country, or same US state find. Statistical analysis from the Met Bulletin is no longer a valid representation of actual distribution. A quick guide is that stoneys are 90%, Pallasites are 6%, irons are 3.5% and the Martians, Lunars, and others are below 0.1%.

Razumiješ? 

billpeters

Edited by billpeters
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Ok, that kind of makes sense.... maybe. I still find it surprising that meteorite finds have become so common that all the testing labs are basically overwhelmed. I believe that even the 'common' stones are rare enough that there is definitely a market for them and if you plan on  selling them, you basically have to have some kind of a certificate. This also doesn't explain why the NWA Lunars have been stable at about 3/year for 10 years and then in 2013 it suddenly jumps to close to 30/year and remains stable at than number. Maybe it's really a change in a level of education but that jump is huge.

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