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Accretion to the collection - what a glorious day

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#1 ZielkeNightsky

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Posted 18 January 2014 - 02:37 PM

If you lookup the definitions for “accretion” in a dictionary, one definition will be:

((astronomy) the formation of a celestial object by the effect of gravity pulling together surrounding objects and gases)


This can translate into:
((meteorites) the formation of a celestial collection by the effect of a thrive to explore, pulling together surrounding objects of our origin)



The later was the case today. For some time I’ve been looking for some irons to add to the collection and today the first new specimens arrived.

The first specimen is a nice Seymchan that probably won’t stay to long in the collection. But for now I’ll study and enjoying it.

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more to come :jump:

#2 ZielkeNightsky

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Posted 19 January 2014 - 09:04 AM

Here's a couple of pics of an oddly shaped Campo. A new member in the collection.

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stay tuned....

#3 Dave M

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Posted 19 January 2014 - 10:21 AM

Nice specimens..

#4 ZielkeNightsky

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Posted 19 January 2014 - 12:35 PM

A couple of small Henbury was added. Here is some images of the small etched slice.

The colour is not faithful, because here I used some monochromatic light to bring out the widmanstätten patterns.

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The pictures is taken on black piece of glass and if you examine the reflected image, you will notice a bright rim around the widmanstätten patterns. After some experimentation with the light angels (must be within a few degrees) I got the details of these crystals out. I'm not sure what's them rim is called, anyone?

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Stay tuned.....

#5 ZielkeNightsky

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Posted 19 January 2014 - 12:55 PM

And the other Henbury, just 4.2 grams

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Stay tuned

#6 rfinney

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Posted 19 January 2014 - 02:06 PM


Hello Lars:

Great stuff - especially the green crystal in the Seymchan. The photo is a keeper!

I have lots of Henbury individuals but I think your photo is the first etched specimen I have seen. Which makes me wonder why don't we seen more etched Henburys since they seem to be plentiful?

I have a few with strange shapes and a couple picked up by the Meteorite Men on their TV show - but nothing etched.

Appreciate the posting...

- RF

#7 ZielkeNightsky

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Posted 19 January 2014 - 02:20 PM

Thanks for the nice comments.

Regarding etched Henbury. I have another one that don't shows the widmanstätten patterns. It make me wonders is the one below should be re-polished and etched again?

I think I've shown it before, but here it is from the stock.

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#8 ZielkeNightsky

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Posted 19 January 2014 - 02:33 PM

The couple of irons I've unpacked is Sikhote-Alin. Two very different samples in regards to the surface finish.

Does anyone have comments on the difference?.

Here's some pics.

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The larger of the two

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#9 peter scherff

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Posted 19 January 2014 - 02:42 PM

Hi Lars,
The last photo that you posted looks more like a Campo del Cielo than a Sikhote-Alin. THe meteorite appears to have been highly oxidized then tumbled. Perhaps some one mislabeled it?

Thanks,

Peter

#10 ZielkeNightsky

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Posted 20 January 2014 - 06:44 PM

Hi Peter

I did some investigations about the origin. I traced it back to a dealer in Tucson, Arizona (which of course I don't know). There seems to no mislabelling.

Then I compared it to my Campo's and another not so smooth Sikhote-Alin, I'll say it feels more like a Sikhote.

So I decided to photograph the Sikhote-Alins together so the light setup is the same.

Here's the result.
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Here's a few pictures of another Sikhote with absolutely excellent provenance
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Pic 2

This one is more like the odd Sikhote.

#11 contrailmaker

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Posted 21 January 2014 - 12:02 AM

Nice! Thanks for the great pictures.

CM

#12 Paul G

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Posted 21 January 2014 - 06:59 AM

Beautiful specimens, beautiful pictures. Would like to see something in the pic like a cm cube to give it scale.

#13 ZielkeNightsky

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Posted 21 January 2014 - 07:02 PM

Thanks Gus - I'm not so fund of using my scale cube. It's shiny polished surface shows dust to easy and is almost impossible to hold clean. But I do use it.

Here a couple Mundrabilla from the package :jump:

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The next specimen is flat and to my surprise it displayed the most beautiful colours, almost glowing, under macro studio lamps.

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Stay tuned..... :jump:

#14 hfjacinto

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Posted 21 January 2014 - 08:56 PM

Beautiful pictures

#15 Glassthrower

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Posted 21 January 2014 - 10:24 PM

Nice Seymchan. That green crystal makes it a keeper. :)

#16 lee14

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Posted 22 January 2014 - 12:57 PM

The difference between your two Sikhotes is simply the amount of time they passed through the atmosphere as the individuals you now have. The smooth specimen with the nice regmaglypts and dark fusion crust, separated from the main mass higher in the atmosphere, allowing more time for ablation to produce the cavities and the surface to smooth over. The piece that admittedly resembles a Campo is often referred to as 'shrapnel', it was produced closer to the ground, and had less time to form the smoothed, regmaglypted surface generally identified with Sikhotes. Also, because it lacked a fusion crust, the surface was more prone to corrosion after it landed, yielding a more Campo-like appearance.

Lee

#17 ZielkeNightsky

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Posted 22 January 2014 - 01:13 PM

Thanks for the comments. Good information about the Sikhotes Lee.

#18 lee14

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Posted 22 January 2014 - 04:53 PM

Hi Lars,

I think the reason that the Henbury lacks a Widmanstatten pattern is due to extreme shock and/or heating. I sometimes see the same surface appearance when I cut and etch a Canyon Diablo. It will grind flat and smooth, but no matter how long it remains in the etching solution, the only result is that fine grained surface that looks very much like your Henbury. Sometimes bands of taenite are visible and remain bright after etching. Your piece has what looks like curved lines of bright material. This could be taenite compressed from shock deformation, and the curvature would seem to point to extreme stress from shock as well. A nice piece!

Lee

#19 peter scherff

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Posted 22 January 2014 - 05:06 PM

Hi Lee,
When Lars first posted the photos of his Sikhote-Alin samples I was expecting to see a typical “shrapnel” piece as I scrolled down. I was surprised to see a relatively featureless iron meteorite that appears to have been in a rock tumbler. The “shrapnel” samples that I have seen look as if they were torn apart. They have jagged edges, twisted shapes and striations. Lars’ anomalous sample displays none of these features. While it may very well be a Sikhote-Alin meteorite I think the only way to prove it would be to cut it and etch it. I have attached a photo of a typical Sikhote-Alin “shrapnel” sample.
Thanks,
Peter

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#20 lee14

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Posted 22 January 2014 - 06:08 PM

Hi Peter,

Absolutely, it does lack most of the typical characteristics of the shrapnel pieces we're familiar with. The only real feature is that sharp edge on the 'bottom'. To me, it looks like the piece has been wire brushed. That tends to leave the high spots bright, and the deeper pits unaffected. I think that tumbling would leave a smoother, more uniform surface. Of course that would depend on the medium used, a large grade of abrasive would leave the surface much as we see on Lars' piece. I have similar examples of shrapnel to the one in your image, and also more smoothed specimens. I think the appearance depends both on their location on the main mass before it exploded, and the height above the ground. You're right about destructive analysis such as etching being the only way to be sure. A Sikhote of that size shouldn't show any pattern at all, while a Campo may or may not. One thing that leads me to believe it is a Sikhote is that it came with a specimen that is undeniably a Sikhote-Alin from the same dealer, but of course that's not really proof.

Lee

#21 lee14

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Posted 22 January 2014 - 06:24 PM

This is a 99g Sikhote with the classic look of shrapnel. Still, you can see where some of the edges have started to melt and roll over.

Lee

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#22 lee14

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Posted 22 January 2014 - 06:27 PM

Another view.

Lee

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#23 lee14

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Posted 22 January 2014 - 06:33 PM

Here's one that's still shrapnel, but it's rather bland compared to the 99 gram specimen. You can see some typical shrapnel features such as striations on one side, but the surface on the reverse side looks very much like the one that Lars has imaged. (23 grams)

Lee

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#24 lee14

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Posted 22 January 2014 - 06:34 PM

The reverse side...

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#25 lee14

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Posted 22 January 2014 - 06:37 PM

And last but not least, one of my favorite regmaglypted Sikhotes. (32 grams)

Lee

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