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Difference Between these 2 MUONIONALUSTA

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#1 Kent10

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Posted 07 September 2013 - 08:04 PM

These 2 have quite a different patina to them. Were they in different parts of the soil or was one treated? I am trying to figure out how they became so different. Thanks, Kent

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#2 Kent10

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Posted 07 September 2013 - 08:05 PM

2nd

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#3 lee14

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Posted 08 September 2013 - 08:54 AM

Muonionalustas are typically quite weathered, and therefore invite aggressive surface cleaning. Your two specimens which seem quite similar in size and shape have most likely been prepared differently. If you acquired them from different sources, that would certainly strengthen the case. I'm unsure about the lighter colored individual, but I'd guess chemical cleaning was involved, possibly something like phosphoric acid. The other has the look of being cleaned up with a wire wheel, then maybe coated with lacquer.

Lee

#4 Kent10

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Posted 08 September 2013 - 09:12 AM

Thanks for the info Lee. I wish these were mine but I have just been looking at these for sale here

http://www.ebay.com/...sacat=3213&a...

And was curious. The shiny ones seem much more common. They do look like they might have a lacquer on them. They look shiny anyway compared to the other. Is that rust on the duller one? See pic. Thanks again.

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#5 Glassthrower

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Posted 08 September 2013 - 09:25 AM

Be careful with specimens that have been cleaned with chemicals - it often renders them unstable.

#6 lee14

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Posted 08 September 2013 - 09:55 AM

Quite so. Hydrochloric ('Muriatic') acid will remove rust, but leaves behind the dreaded chlorine contaminant. Phosphoric acid will remove rust without the introduction of chloride compounds, but my experience with it is limited to only a couple of small specimens and I couldn't really speculate on long term effects.

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#7 lee14

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Posted 08 September 2013 - 10:09 AM

Kent, the darker shinier Muon has almost certainly been wire brushed and lacquered. I've bought quite a few Campos from this dealer and that's how they've all been finished. I have mixed feelings about lacquer. It definitely prevents damage to the surface from handling, but if there's trapped moisture in the interior, it can accelerate the corrosion process.

The gray Muon definitely has a few rust spots, but that's not necessarily a bad thing. The issue with Muons is subsurface contamination, which can result in 'weeping', i.e. the formation of the greenish-yellow globules on the surface which is an indication of lawrencite disease. There's no way of knowing from the pic if it's been treated and the rust formed naturally, or if a more insidious process is at work.

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#8 lee14

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Posted 08 September 2013 - 10:13 AM

Here's an example of what I consider 'attractive' rust. This is a 24.3 kg Gibeon that exhibits a deep red patina and absolutely no tendency towards ongoing surface degradation. I've had it for nine years and it's my favorite piece.

Lee

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#9 lee14

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Posted 08 September 2013 - 10:50 AM

another view...

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#10 Kent10

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Posted 08 September 2013 - 11:23 AM

Oh yea. That's beautiful Lee. I bought these 2 from this dealer.

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#11 Kent10

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Posted 08 September 2013 - 11:23 AM

And

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#12 lintonius

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Posted 08 September 2013 - 11:49 AM

Here's an example of what I consider 'attractive' rust. This is a 24.3 kg Gibeon that exhibits a deep red patina and absolutely no tendency towards ongoing surface degradation. I've had it for nine years and it's my favorite piece.

Lee


That's a beautiful Gibeon, Lee!
Indeed, 'cleaning' away that patina/rust would be vandalism, in my mind.
Linton

#13 Glassthrower

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Posted 08 September 2013 - 12:49 PM

As Lee said, an oxidation layer can actually insulate the specimen for further and more serious damage. Many iron meteorites found in the field have a thick oxidation rind on them which protects the unoxidized core. When this rind is removed, it exposes the unoxidized material to terrestrial contamination.

If the rust is an aesthetic issue, then it should be left alone, IMO. If the rust is indicative of serious stability issues (weeping fluid, pieces flaking off), then one should consider stabilization measures.

#14 lintonius

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Posted 08 September 2013 - 12:49 PM

Nice etch on that one, Kent.
Here's the nicest Muonion slice I've had.
It's moved on to the Falling Rocks collection now.
Linton

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#15 Glassthrower

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Posted 08 September 2013 - 12:50 PM

I love that graphite inclusion Linton! :)

#16 lintonius

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Posted 08 September 2013 - 12:57 PM

I love that graphite inclusion Linton! :)


Thanks Mike.
I couldn't remember if it was graphite or troilite.
Anyway, I always thought of that slice as 'Snoopy'... and that was his eye! ;^)
Linton

#17 Kent10

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Posted 08 September 2013 - 01:12 PM

Nice etch on that one, Kent.


Thanks Linton. I was looking for a nice etched something and was considering a MUONIONALUSTA. I liked it but the more I looked at the Gibeon and considering how stable they are I decided to get it. The MUONIONALUSTA was etched on only 1 side which is kind of neat because then you can see something different on the other side. Do people generally prefer a full slice over an end? And is one more valuable than the other? It seems to me they are about the same price per gram but the ends are usually thicker and so usually weigh more if the surface area is the same.

#18 lintonius

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Posted 08 September 2013 - 02:22 PM

Thanks Linton. I was looking for a nice etched something and was considering a MUONIONALUSTA. I liked it but the more I looked at the Gibeon and considering how stable they are I decided to get it. The MUONIONALUSTA was etched on only 1 side which is kind of neat because then you can see something different on the other side. Do people generally prefer a full slice over an end? And is one more valuable than the other? It seems to me they are about the same price per gram but the ends are usually thicker and so usually weigh more if the surface area is the same.


Value is subjective, Kent. End-cuts are always nice, since you get the look of a whole individual, plus the interior on one end. But you can get a lot more surface area per gram (per dollar!) with a slice. And that applies to stoney meteorites, as well as etched irons.
Linton

#19 lintonius

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Posted 08 September 2013 - 02:29 PM

I love that graphite inclusion Linton! :)


You like inclusions, Mike? Check out this one!
Not for sale... ever.
Linton

494.2g Gibeon 'obelisk'

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#20 lintonius

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Posted 08 September 2013 - 02:31 PM

Another view...

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