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Have the reverse-skeletal Madan galenas been faked?

Posted by Patrick Haynes (2)  
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 28, 2010 04:00PM
    
Does anyone know good solvents for galena? I would think the the "terraces" seen on the galenas represent very slow etching. Rock, have you tried abrading a galena, then slow etching to remove the roughness and possibly produce terraces? From research with my co-author Bob Morgan looking at carrollite from Kamoya and pyrite from Huanzala and elsewhere, terraces seem to be slow etch features. terraces seem to be formed according the PBC (Periodic Bond Chain) growth/dissolution models. To make a fake look better, the air abrasion would be done first and chemical treatment could follow that process to restore the luster and introduce etch features such as terraces. The choice of solvent would probably produce different effects, so much experimentation would be necessary. On the photos shown, the smallest crystals do not seem to be skeletal. There are, of course, many etch features which seem to be naturally present on Magadan galena.

Best Wishes, Van King
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 28, 2010 04:39PM
    
I have been holding my tongue on this, but that would be the next stage of fakery. Once the abrasions and indentations are obvious, one merely washes them away. How's Jessica's experiment coming?
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 28, 2010 10:31PM
    
It seems to me that the "terraces" could easily be exposed growth layers rather than a feature caused by etching. Refer to Ryan Bowling's post on page 3 of this discussion for photos of a hollow galena cube he created. His photos show a similar step or terrace pattern from his 10-minute air abrasive carving work, which implies no etching is necessary to create this pattern. For me, his post was the most convincing that these galenas could be produced artificially.

I am also wondering how the Simonoff's experiments are going - any updates?

Best regards,
Jonathan
Re: Have the reverse-skeletal Madan galenas been faked?
July 29, 2010 10:07AM
Here is the galena in the "A.G. Werner collection, TU Bergakademie Freiberg, Saxony". You can see this specimen in the display showcase of new acquisitions. For me it is hard to believe, that they exhibit anything faked in this magnificent historic collection. Although i would say it is maybe from Madan district and not from Laki.

Whats about the SEM investigations and things like that, which were held in prospect?
Meanwhile we can discuss and philosophize further on if they are "faked....semi faked.....natural.....etched......and so on....."
It is a very interesting discussion for me, also from the mineralogical aspect winking smiley)

Regards from austria,
Erik
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avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 29, 2010 10:30AM
I don't think anyone doubts that features such as this can be created naturally.

But the question is, are some of the specimens created to look as if they are naturally etched galena when they are not?
Re: Have the reverse-skeletal Madan galenas been faked?
July 29, 2010 11:58AM
Again, we are comparing apples and oranges here. The depicted Bergakademie specimens are not the centre-less galena "frames" that this discussion is about.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 29, 2010 01:06PM
If you want features that look more etched than broken, just use a smaller glass beads.

Rock Currier
Crystals not pistols.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 29, 2010 02:14PM
    
Exposed growth layers are part of the Periodic Bond Chain growth/dissolution models and these models also relate to the origin of striations (growth layers) which are generally many thousands of unit cells high. Terraces such as striations are generally growth features, while terraces that are asymmetric are usually dissolution features. The wavy pattern seen on many Madan galenas are certainly the result of relatively slow dissolution whether natural of artificial. I saw Ryan Bowling's photos originally before posting and they do show the possibility of creating the skeletal appearance, in general character. The terraces are exposed abraded cleavages. Rob's specimen shows the subtleties of rounding and smoothness not present in Ryan's photos. The subtleties are key to whether abrasion alone can duplicate the process in detail. Of course, being able to exactly duplicate the specimens seen is not proof that the specimens are faked; merely that they can be faked.

Best Wishes, Van King
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 02:25AM
    
Hello!
I just finished writing the article. I will update it when I get new information and photos. I will get micro-photos and, if it will be helpful, I have permission to use a SEM and XRD machine. You can see the article here: Galena article

I am looking forward to your comments and thoughts about what might help!

Jessica
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 03:12AM
    
What a great article!!! Excellent observations. The point about galena's symmetry, so all symmetry related faces should etch similarly, is new. One could plead that the contact faces were not accessible and so not exsolved, but the pleading gets a little special when hard to get at faces are involved. I look forward to the SEM images. I doubt that the surface recrystallizes as Gold does, but electron diffraction off an abraided surface ought to be very diffuse.

If these are fakes as some suspect, they are truly great fakes and should certainly hold their value. There was a great Min Rec issue on fakes years ago and I would have thought that would have created an interest in these as mineral ephemera.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 03:34AM
    
Fantastic - looking forward to your further analyses! Very interesting that an obviously undamaged calcite crystal is within the hollow of one of these...

Best regards,
Jonathan
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 03:47AM
    
That calcite does have extremely minor damage, far less than I would have thought abrasion would have done. With Galena at 2.5 Mohs and Calcite at 3 Mohs, there is not much room to pick an abrasive that would leave the calcite virtually untouched.The calcite is a lovely surprise.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 03:48AM
    
We will be posting microphotos of that calcite as its shape is very interesting once you get close up smiling smiley
Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 10:49AM
what a fantastic thread, and article...... captivating as much as the specimens in wich we r talking about.


............andy
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 12:43PM
might want to google electropolishing... if I can find some apprpriate samples and electrolytes. I might devise some testing to produce similar effects, not just in galena but perhaps pyrites and/or chalcopyrites, since all three are semiconductors and should pass current.

Electropolishing amd/or EDM/ECM could conceivably produce some unique specimens that may be exceedingly difficult to tell from natural etching. I've worked in metals for decades, and have seen similar localized structures in various alloys when electropolished.

stay tuned...

auplater
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 01:15PM
    
Thanks everyone!! :)
Jessica
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 04:40PM
    
I am highly biased to believe the majority of the skeletal galenas are a natural phenomenon. This is because the only galena I have ever found had portions with this skeletal effect:

skeletal_galena_pic

As you can see in this UNTREATED SPECIMEN, the corners of the galena cube form a thicker cerussite/angelsite alteration coating than the cube faces. This alteration coating then acts as a protective mask for the corner edges while some fluid dissolves the rest of the cube, starting in the center of the faces, but producing curved etch surfaces as any isotropic etchant would. If the etchant chemistry sometimes etches the alteration coating, but at a different rate, you would expect the galena etch surfaces to have a scalloped effect (curved ridges).

I suspect that any remaining alteration coating has been removed from the skeletal galenas in question because it would not look as pretty as bright gleaming specimens. Wouldn't it be great to see pictures of these galenas in situ?

-Dean Allum
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 05:31PM
    
Great article Jessica! I haven't formed an opinion either way, just waiting for all work to be completed first. However, I want to believe they are not faked. They definately are fun to look at regardless. The calcite sure brings an interesting twist. Keep up the good work Jessica! -D
Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 06:14PM
Dean-

I can't be certain, but your photo appears to show the "boxwork" texture that is common in weathered sulfides. Secondary minerals grow in between crystals and along cleavage planes as the sulfide breaks down/oxidizes during the weathering process. When the sulfide is gone, you are left with the "boxwork" of secondary minerals. I'm not sure this phenomenon could be called upon as an explanation for the "skeletal" features displayed in the Madan galenas in this thread.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
July 30, 2010 07:09PM
    
James is right. If you could get the secondaries off the box work, you would find it quite pitted unlike the skeletal forms in question here.
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