[meteorite-list] metal-rich diogenite vs mesosiderite-C

[j.divelbiss at att.net]

Joern and David,

In my first inquiry this week I mentioned NWA 1882 (not 1982 that Joern and David touched on) as being the same material. It is my belief that NWA 1882 is the same material as NWA 1827/1879. Stefan Ralew, who sold 1882 to me, also believes it to be the same. NWA 1882 was not classified MES C per say, and I've read/heard no mention of it being the same material officially, though there is mention in the latest bulletin that TKW was now over 22 kilos for the MES C finds.  

So we may eventually end up with the MES C material from NWA to include 1827, 1879, 1882(maybe) and 1982 (maybe). In any case I think it is one of the nicest meteorites I have. Here is Stefan's site for the NWA 1882 material. At $8/g...you will be hard pressed to find a nicer meteorite. Even his pictures don't do it justice.

http://www.meteoriten.com/stonyirons.html

Enjoy,

John

-------------- Original message from David Weir : -------------- 

> Hello Jörn, 
> 
> Since nobody "in the know" has answered your ponderings yet, I think 
> I'll add my take on this circumstance. I followed the progress of 
> analysis of NWA 1827 because I had seen the piece that Nelson had 
> acquired and I thought it had a unique and interesting appearance. The 
> preliminary analysis had considered that the data best fit a 
> classification as a recrystallized, metal-rich diogenite, which was 
> intruded by an exotic metallic body and annealed within a deep regolith. 
> 
> In a paper by R. Hewins (1988) a similar description was given for 
> RKPA79015, but which was taken to be a diogenitic end member of the 
> mesosiderite body. In a similar way, Clark and Mason (1982) had much 
> difficulty in their original attempt to classify RKPA79015 (Haack et 
> al., 1996). They finally used the widths of tetrataenite rims on 
> taenite to arrive at a classification of mesosiderite for this 
> meteorite. 
> 
> Anyway, after extended analyses scientists at NAU determined that NWA 
> 1827 is also consistent with a type 2C meso, fantastic news for us type 
> collectors (I guess this is still tentative though). 
> 
> In addition, the abstract to which you refer I believe was the final 
> result of a joint effort by both labs (NAU and UWS), which superseded 
> the original classification of NWA 1982, now thought to be more likely 
> paired with this type 2C meso. That's my take. 
> 
> There is further information on the many difficulties of classifying 
> this type 2C meso on my NWA 1827 webpage. 
> 
> David 
> 
> ----------------------original post-------------------------------- 
> 
> It seems, there is a problem with the class C mesosiderites and the 
> metal-rich diogenites, which may just be fragments of the same meteorite 
> shower. 
> 
> In the last Met. Bulletin 88, the following classifications and remarks 
> are given: 
> 
> NWA 1982: an ungrouped achondrite "not paired with NWA 1827 or NWA 1879 
> mesosiderite" 
> 
> NWA 1827: mesosiderite (tentatively classified C) "resembles a 
> metal-rich diogenite... [but is] part of a large, heterogeneous 
> mesosiderite containing sparse eucritic and diogenitic clasts" 
> 
> In the abstract by T. E. Bunch et al. (2003) MAPS 39, no. 8 (Suppl.), 
> p.A19, which is the same MAPS issue with the Bulletin 88, the authors 
> conclude that NWA 1827 and NWA 1982 are paired and that they "could be 
> misidentified as "metal-rich diogenite." 
> 
> So, at least for NWA 1982, we have a clear ambiguity between these two 
> references. 
> 
> Best regards, 
> 
> Jörn 
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