[meteorite-list] iron meteorite natural color
From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Sat, 26 Nov 2016 16:45:34 -0500
I'll try to give you a little more insight on your questions from my point of view and then write about what is practical to do. It is important to stress "point of view" because in the end you will probably do with your meteorites whatever makes you happiest, which clearly the impulse at this point is a jet black cosmetic preference of smooth black which I do not like when it is a synthetic laboratory process.
First, you initially you asked:
"As we know an iron meteorite, such like Campo del Cielo for example, have a black surface. I have here a deeply rusted Campo, I'm planning to remove rust with a sand blasting process. But with this I will obtain a grayish surface, like naked iron, the same color of a slice."
This is *not* "as we know". I do not know of Campo meteorites being recovered with black surfaces, do you or anybody else know this? I never personally had the good fortune to recover a Campo myself so it it my assumption. I have recovered other iron meteorites. All are light or dark orange rust color except one locality that actually was naturally weathered to black.
So I feel your original premise of "as we know ... Campo ... black" is a false premise. Is it based on a mixed series of assumptions maybe due to equating space, mystery, adrenaline, and night to blackness, seeing some naturally blackened weathered meteorites, imagining a stony meteorite fresh crust for your iron, and maybe never seeing a freshly fallen iron meteorite that has not be cleaned and altered its surface by sellers for markets such as jewelry where a concept is being marketed and not what is "natural"?
Rubbing mineral or other appropriate oil and if you are serious like hinted by Marcin, dry, quite gentle oven heat will darken the metal, the later also mentioned by Marcin.
The initial fall fresh probably had a blue-gray color, like metal heated in a furnace. It is somewhat darker but the coloring is the fusion crust. Your Campo has lost its fusion crust a long time ago. If you have an uncrusted ordinary chondrite fragment would you also want to treat the matrix surface to turn it black? No! What you have exposed it the interior, in its natural color. Now you want to make it dark.
OK, so you work so hard to removed all the oxides/rusts and chlorides, and now you want to treat it to return them. Only this time you want to do it in a controlled fashion to fake the look of natural weathering.
Let us look what nature does. If it is fresh and dry, it can blacken and leave intact real fusion crust. Most likely though, it will fall in a humid environment and rust orange and form some surface scale or shale. Sometimes you can get a tough rather orange, near black, coating like Gibeons can appear on the market. But let's instead think of natural.
WHAT IS NATURAL? (asks Pilate!) Natural is a very gradual and slow process in which oxidation takes place, perhaps not too deeply as to preserve smooth fusion crust in many finds and falls. It requires many many cycles of: oxidize lightly, oxidize uniformly, clean (perhaps by wind abrasion and washed by distilled rain, even acid rain is effective.
Now you want to falsely reproduce that process on the matrix of a long rusted meteorite that has been pickled in aggressive caustic chemicals. That's gross! It is like skinning off the hide of an animal and then coloring its remaining carcass the color of fur for display instead of the natural colors of the muscles, fats and organs.
OK, but you still want to do it and don't agree with me. There are more problems. The naturally colored meteorites that are black or orange and have little to no scaling and original layers of fusion crust at the least alpha-2 layer, may be significantly impervious to seepage, but your Campo has already developed cracks, faults internal cavities from rot that was removed, due to thousands of years un soil and rain, powerful roots, expansion and contraction by temperature changes, and general oxidative terrestrial processes, solubilization of corrosive catalysts you.ve removed, you hope.
My point is you can color it however you want, but the fake coloring will be misleading, it will not have inside a weathering-naturally stabilized meteorite and its internals due to their porous and fissured nature will not be as represented. The more you do to an iron to make a faux patina, possibly the more you will need to work to redo regularly. The more it is handled the more contaminants will get into it from sweat, etc. And!!! to make that false patina fool those to think it closer to natural, you must dig into the surface of your material and oxidize it in a controlled manner, further weathering the piece of bright matrix you cut (not with a saw but with chemicals).
The simplest things are: degrease with acetone if you are serious, then dry gentle heat a few hours followed by a good oil and you will build up a light protective oxidation layer. If you use any of the aggressive chemicals you have mentioned after cleaning you will reintroduce them. This is not a smooth surface you can just wipe them off. The get sucked in.
Finally upon removing from the oven you can instead soak them like hot potatoes in hot paraffin or other of these microcrystalline waxes and oils. Hot, so it is absorbed into all those crevices that have been created by you removing the oxides and nature's ambient forces beating the buried meteorite. The a little of the oil when all is cooled every now and then wont's hurt on the surface and is the easiest way to keep things in check.
Hope that helps more! I apologize for my point of view but it is based on my idea of what a meteorite "should look like" which is an emotional concept and I agree here that this is only my personal opinion, authentically conserving whatever characteristics of the locality possible, and balancing that with preventing rampant oxidation. It is like cleaning coins. The only thin worse than a cleaned coin is one that has been cleaned and then colored in some way to hid the fact it was cleaned, usually to sell for more as a coin that never was cleaned will fetch from buyers.
Other options besides paint, are VCI systems to preserve professionally used by some hard core collectors, and electroplating metals used for jewelry ... You can even try silver which will be initially bright but will soon turn very black!
(Feeling like H.H.Nininger now when he bellyached about people etching iron meteorites with a border of shellac on the slices to leave a very "unnatural" etch of the slice. He felt this would be detrimental to people understanding what a meteorite truly looked like and do a disservice to meteoritics. Notwithstanding, this practice had become popular amount some nowadays as ol' H.H. rolls over...)
From: Francesco Moser via Meteorite-list <meteorite-list at meteoritecentral.com>
To: Meteorite-list <Meteorite-list at meteoritecentral.com>
Sent: Sat, Nov 26, 2016 11:20 am
Subject: [meteorite-list] R: iron meteorite natural color
Marcin and Doug!
Thanks for your replys!
Ok, I understand what you mean about the authenticity of color.
For sure the desert varnish of some iron meteorite like Gibeon or Henbury is
the most natural looking for a find (not fall) meteorite.
But old and buried meteorite like Muonionalusta or Campo have a very thick
rust and oxide crust, I suppose no one want to have that on his irons.
So after remove and clean all the rust shale what remains? Grey nude iron
... it is absolutely not natural!!!
So for me on this type of meteorite the black surface is something better
that the nude iron, isn't?
Of course I don't want to paint the meteorite, just convert the nude grey
iron to dark.
How it is possible? With oil?
All the Campo that are on the market have nude dark iron on the surface, how
can I reach the same looking starting from nude grey iron results of sand
Da: Meteorite-list [mailto:meteorite-list-bounces at meteoritecentral.com] Per
conto di Marcin Cimala - POLANDMET via Meteorite-list
Inviato: gioved? 24 novembre 2016 23:42
A: Meteorite-list at meteoritecentral.com
Oggetto: Re: [meteorite-list] iron meteorite natural color
> I have a question.
> As we know an iron meteorite, such like Campo del Cielo for example,
> have a black surface.
> I have here a deeply rusted Campo, I'm planning to remove rust with a
> sand blasting process.
> But with this I will obtain a greysh surface, like naked iron, the
> same color of a slice.
> Not really a natural color for the exterior of an iron meteorite and
> also not aestetically pretty, looks too artificial for me.
> There is something to do for restore the original black color?
> Or it's better to remove the rust with a traditional steel brush,
> maybe with a drill ???
> Tips for mechanical or chemical process are welkomme!!!
> I can try with the classical NaOh bath, I have also Phosphoric, Citric
> and Oxalic acid :)
Hah good question Francesco. But what is natural color of meteorite at all ?
Desert sandblasted NWA is not a real looking meteorite? Should I paint them
black to be looking like a real meteorites ? Poor Dhofars....
This is what Im fighting long time. Strange stereotype that meteorite MUST
BE BLACK outside, WHY ?
When You like Your girlfrend ? When he smile to You with his pretty face or
when she put ton of Max Factor chemicals on it??
I have always strange taste, different than most of collectors. For me, if
specimen have crust must be black or black with rusty patina. If meteorite
have no more crust like Campo, why to "paint" it to black to looks like
Sikhote ? Then You will see paint, not Your meteorite. I only can imagine
what strange things they do to clean Campo and look it like that. LOL
OK now a few tips.
As I understand Your Campo is a complete specimen ? To remove deep rust You
must use electrochemical cleaning + brush + small hammer. Then You will get
mostly cleaned meteorite with BLACK remains of rust that will make Your
meteorite looks REAL.Then heat it and put alot of oil to make it looks fresh
and oriented :)
-----[ MARCIN CIMALA ]----[ +48 793567667 ]-----
--------[ Member of Polish Meteoritical Society ]--------
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