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Natural Sikhote-Alin

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#1 Kent10

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Posted 13 September 2013 - 04:51 PM

I just received this Sikhote-Alin and I like it.

Most of the ones I have seen have the same coloring/patina.

This next one has a different "natural" patina as described by the seller. What is the difference. Were the "unnatural" other ones treated? I wonder if that is preferred then because most are like this. Thanks.

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#2 Kent10

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Posted 13 September 2013 - 04:51 PM

Natural

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#3 Kent10

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Posted 13 September 2013 - 05:31 PM

The color of this one is also different. Nice!

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#4 lee14

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Posted 14 September 2013 - 09:34 AM

I'm thinking the 'natural' one is simply uncleaned. I have quite a few Sikhotes in that size range, and after some gentle cleaning and an application of gun oil, they all have that dark appearance.

This group of Sikhotes appears how it arrived to me from the field collector, before cleaning or oiling.

A word or two about crusts on irons; what is commonly referred to as crust, is generally a layer of rust that is the result of long, slow degradation in the terrestrial environment. Sikhote-Alins, being a relatively recent fall (1947), frequently retain their original fusion crust. That is what appears dark, as fusion crusts in general do. Some Sikhotes show flight markings such as flow lines and rollover lips. Both of these features are present to some degree in the top image. The crust on these is typically thin, and rather delicate, you can often see where parts of it have flaked off revealing the thickness of the remaining portion. Any Sikhote with a dark crust like this should never be aggressively cleaned, ie. no wire brushing, and certainly no chemicals.

Sikhotes come in two varieties, the nicely crusted specimens you've pictured above, with genuine dark fusion crusts and an abundance of regmaglphs. These are generally the preferred individuals sought by collectors. The other kind is the 'shrapnel' pieces, which separated from the larger mass later in their flight through the atmosphere and had insufficent time for the surfaces to ablate, melt, flow, and form a crust. They can show a lot of surface detail, but it's related to stresses and fracturing.

Lee

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#5 lee14

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Posted 14 September 2013 - 09:49 AM

This is a piece that I'd call shrapnel. Lots of stress marks from the explosive separation, and you can see the beginnings of a rollover lip, but no regmaglyphs or fusion crust. It's relatively rounded though, and given a little more time to heat up in flight, would have developed both features.

Lee

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#6 lee14

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Posted 14 September 2013 - 02:35 PM

This is a more extreme piece of Sikhote shrapnel. It's a seriously tortured hunk of metal, at 99 grams and 2 3/4 inches in the longest dimension.

Lee

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#7 lee14

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Posted 14 September 2013 - 02:40 PM

Another angle...

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#8 lee14

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Posted 14 September 2013 - 02:44 PM

Other side...

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#9 Kent10

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Posted 14 September 2013 - 02:48 PM

Thanks for all the information, Lee. I like your shrapnel. Yes that one is quite tortured. Here is my Sikhote shrapnel.

The piece with the blue background looks more silvery than dark. I wonder if it is just the lighting.

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#10 Kent10

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Posted 14 September 2013 - 02:48 PM

Other side.

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#11 Kent10

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Posted 14 September 2013 - 06:54 PM

Here is some more interesting info on the crust

http://www.asteroidc...Alin_Crust.html

#12 lee14

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Posted 14 September 2013 - 08:55 PM

Interesting article indeed. I'm pretty sure the group I imaged above and the others I purchased around 2005 were collected close to that time. They were from a field collector in Finland who was selling quite a few lots in the kg range, of small stones. The large lots petered out after a couple of years, and then more lots of shrapnel started to appear.

Lee

#13 choran

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Posted 26 October 2013 - 08:43 PM

I've got one from the same fall (one of only two that I own) and it looks very similar to the first picture. They are just great looking!






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