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Have the reverse-skeletal Madan galenas been faked?
Posted by Patrick Haynes (2)
Patrick Haynes (2) October 26, 2009 12:37PMI have always suspected that the reverse-skeletal galenas we have been seeing from Madan, Bulgaria had been manufactured by "sandblasting" existing specimens. I expected to see only an initial few, but now they seem to be at every show. Other opinions?
Jolyon & Katya Ralph October 26, 2009 01:27PMI think they're highly suspicious. Just to clarify, we're talking about skeletal galenas where the forms look irregular and rounded, as if the insides of the crystal are dissolved, and not those where they have clearly crystallized in a sharp skeletal form.
I have had dealers tell me that they trust their sources and believe they are genuine, but Rock Currier was able to replicate one of these specimens by taking a Michigan Galena and 'sandblasting' the centers of each cube. I'll let him explain more about what he did.
The eastern european mineral suppliers aren't short of a trick or two - we've had fake realgars and of course the fake smoky quartzes from Romania, so it doesn't surprise me one bit that some enterprising miner could have been fabricating these things in a hut somewhere and selling them on to unsuspecting mineral dealers.
Proper analysis should be able to determine whether the structures are caused by physical abrasion or chemical etching.
One does wonder what chemical conditions could etch the insides of DIFFERENT SIZED galena crystals on the same specimen at the rates required to leave just the perfect outside shell!!!
Jasun D. McAvoy October 26, 2009 04:00PMFor what its worth, I have wondered the same thing. A good friend and someone who has been very active in the hobby for decades told me that he actually witnessed one being created. It was not the total creation of a fine specimen, but rather a demonstration to simply show that indeed it could be done and how it could be done. I was told that the results were very similar to the specimens being sold. That being said, I have seen a few specimens that really impressed me in that, if they were created, they would have had to been done with a VERY skilled hand in a way that seemed nearly impossible to do because of multiple crystals/clusters/orientations etc.
When I spoke to one dealer from Bulgaria a few years ago in Tucson he told me that they were from an old, one time find and had been stowed away for years and that this was the ONLY source of this material known. This to me, would be the kind of story you'd need for faked specimens. Otherwise we should know about its exact source, who is producing the material and see examples of it in situ. Does anyone know more about the story behind these pieces?
Joseph Polityka October 26, 2009 07:02PMHi,
I have had suspicions from the day I first saw these specimens. They are just too symmetrical and too clean to be natural. I was offered some of these specimens and turned them down because they seemed questionable and, frankly, are way overpriced for what they are.
Rock Currier October 26, 2009 07:17PMI was one of several people that were instantly suspicious of these cavernous galenas when I first saw them. As soon as I got the chance I made one on a small air abrasive unit I had. They are simple to make if you have a small air abrasive tool and a galena cube. Use glass beads and about 80 psi air and in about ten or 15 minutes you can make one of your own. Other friends of mine also were able to duplicate these types of specimens. One made a very attractive one using octahedral galena from Sweetwater, Missouri. Another, only as a lark, using carborundum grit made a nice one out of fluorite. I suspect that we will see these coming to market soon from eastern Europe as soon as the idea occurs to them. Use diamond powder and I suspect you could make them out of spinel octahedrons if you wished. There are a lot of possibilities. But like the new spectacular wire silvers from Germany, it is not easy to prove that they are definitely fakes. I for myself, would not want one in my collection except as a joke to show friends. For specimens like this shown on Mindat, at the very least there should be inserted a comment that some knowledgeable people suggest that you take into consideration that they might be fakes at least until such time that they can definitely be proved to be natural.
Crystals not pistols.
Edited 1 time(s). Last edit at 10/27/2009 12:02AM by Rock Currier.
Alfredo Petrov October 26, 2009 07:49PMI agree with Rock's implication that, in cases like this, the burden of proof is on the suppliers. As Jolyon sometimes says, "Extraordinary claims require extraordinary proof". (Hope I'm not misquoting you, Jolyon.) It's not up to us to prove fakery, the suppliers should prove natural origin. (Samples before cleaning? Samples in situ? Samples with secondary minerals growing on the etched parts?)
Jolyon & Katya Ralph October 26, 2009 07:59PMThe "extraordinary claims require extraordinary proof" statement was from Carl Sagan (and possibly others before him). He used it when discussing things such as UFOs. These odd galenas may not quite be in the same category of incredulity as UFOs but I don't think they're far off.
Bri Dragonne October 26, 2009 08:36PMIs this : http://www.mindat.org/photo-146158.html what we are talking about? (I am not stating that this is person's Galena is a fake, just asking a question...)
I do gem carving and I personally (Given the right blasting equipment) could make something similar.
One thing that strikes me as odd is that it seems that the whole exposed surface of the material is the exact same texture and lustre.
It also seems odd that the weathering shows the Galena 'layers',.
'One does wonder what chemical conditions could etch the insides of DIFFERENT SIZED galena crystals on the same specimen at the rates required to leave just the perfect outside shell!!! '
This also is probably the best point that has been made.
I too wondered about this...
If one has a crystal that is quite large and 65% of the inside of the crystal is removed, how does it happen that a crystal that would fill this 65% of space inside this larger crystal also has about 65% of the inside removed...?
Jolyon & Katya Ralph October 26, 2009 09:34PMYes, Bri.
That's the sort of thing we're talking about.
Here's a better example:
This shows what i'm talking about with smaller and larger cubes, all etched to a relatively constant amount, I'm not sure how that can be explained through any natural phenomena!
I hope that Rob won't feel I'm singling him out here. MANY other dealers have had these, it's just unfortunate that his photos were handy here.
Roger Lang October 26, 2009 09:46PMRock,
please show a photo of those mentioned air abrasive fakes ... IMHO it would be VERY difficult to create a specimen like Bri referred to. The Madan area is known for very interesting and in great parts VERY skeletal galena habits .. most may be treated with phosphoric or anything else to get lustre back but i have a specimen in my collection which i wouldn´t have thought of being man-made as it seems very hard for me to achieve clean crystallographic features with an air gun. I have to admit that my specimen is a cluster of highly lustrous skeletal gonderbach twins on highly lustrous quartz (which should be affected with glass bead air abrasive) and this may be different to the specs you mention but this may be a similar discussion to the Imiter silver.
And i am more convinced that Imiter silver can be faked more easily .... show me a definitely man made galena of this kind pls,
Knut Eldjarn October 26, 2009 09:57PMHi Jolyon,
I am glad you state that you only use Rob`s photos because he has been so generous in uploading photos to Mindat. I know Rob is very particular with the identity and background of the specimens he is selling, but as you have stated these specimens have been handled by a number of dealers also before being offered by Rob Lavinsky.
The idea of them being manmade is very intriguing and can explain why they do not have any alteration which would be expected if found in clay as the story goes. I believe the water in the clay would react with the galena forming secondary minerals in the outer layers of the crystals. Such alterations are quite common on chuncks of galena left in clay and soil on dumps of old mines proving that they form quite fast. IOf later removed by cleaning the specimens these secondary minerals would leave corroded and pitted surfaces on the galena. Another suspicious thing is the fact that at first they seemed to be quite rare - then suddenly more of them turn up. There are similarities to the way native wire silver specimens from Germany and Marrocco emerged on the market. And just like these silvers, the Bulgarian specimens show great uniformity in associated minerals. This is unlike i.e. native silver specimens from China or Kongsberg where habits and associates are much more variable. It would be very interesting if somebody could throw more light on this subject.
Jolyon & Katya Ralph October 26, 2009 10:30PMRoger - I do hope you're not just trying to believe something because you have a specimen!
The only way to be sure is to do some research. Someone needs to come up with a credible natural explanation that covers the formation of these, I'm sure it should be pretty easy to telll abraded galena from naturally deposited stuff.
I really hope they are natural. But it seems too suspicious right now to just be a happy believer.
Innocent until proven guilty doesn't count in science. The only proper way to approach it is to assume it's a suspicious unless proven natural.
Anonymous User October 26, 2009 10:49PMWhy not look at it under SEM? Would natural etching be differentiable from a mechanically abraded specimen?
Also, how would such a natural etching mechanism occur? Is it not easier for chemicals to attack the exterior (especially corners) where there is more contact surface for the volume?
Roger Lang October 26, 2009 10:53PMJol,
nope i do not .. my specimen is way different (will post it when done photos and you will see why ).. but i did some research on hydrothermal deposits before (during my long time gone university career as an ore geologist) and until now here was no clue/evidence etc given to be those fakes .. i have seen many formations by changing of hydrotherms so in dubio pro reo for me .. until Rock doesn´t show me a photo of a man made galena like this i am more into the natural origin. And you know that i am aware of fakes. I definitely won´t rule out a man made origin .. but for me hard to achieve (not mentioned the possible chemical treatment to regain lustre which is common).
Bri Dragonne October 27, 2009 12:22AMI think a way to settle this would be so take one of these specimens and give it a good, thorough wash in a clean ultrasonic cleaner.
Then, pour out the water or whatnot and see what residue is left.
Take the residue and examine it under a microscope and see if we get any micro-abrasive material
I sincerely doubt that they could do this with a blaster and not leave at least a few particles of micro-abrasive.
If none was found at all, it would be interesting.
But the evidence, even if the specimen was previously cleaned, should still come out if cleaned and the residue examined.
Just an idea.
Jolyon & Katya Ralph October 27, 2009 10:14AMIt's an interesting idea Bri, but assumes no-one else has cleaned it in an ultrasonic before. It also doesn't rule out the possibility that they were genuine natural skeletal crystals encased in a hard clay where an abrasive tool was used to clean it out.
The only way I think its to examine the surfaces at high magnification looking for signs of abrasive damage as opposed to either chemical etching or natural growth patterns. They should all be fairly easy to differentiate.
Jolyon & Katya Ralph October 27, 2009 11:09AMHere are a couple of articles regarding natural skeletal galena from Bulgaria. Note that none of the forms in these articles in any way resemble the hollowed cubes we see in the photos before.
As I said in my very first message in this thread, we need to be careful to distinguish between what are clearly genuine galena forms (such as those shown in the PDF) and those hollowed-out cubes we're discussing.
Evan M. Johnson October 27, 2009 04:50PMDoes anyone have access to this paper?
Transition from Isometric to Skeletal Crystal Shapes
V. Tonchev, Prof. Dr. Chr. N. Nanev
Institute of Physical Chemistry Bulgarian Academy of Sciences acad. G. Bonchev, bl. 11 1113 Sofia, Bulgaria
Of all the places the authors could have been from....
Alfredo Petrov October 27, 2009 05:26PMLet's be clear that these features are etch or erosion features (artificial or not), not skeletal growth. You can't have skeletal growth only on edges, without a center. So the fact that very skeletal galenas exist in Bulgaria is irrelevant to this discussion.
Evan M. Johnson October 27, 2009 05:43PMI actually meant it somewhat jokingly. Still, a funny coincidence.
As for the differential etching of large versus small crystals, wouldn't that be because it's the surface area that's the relevant feature in determining the rate of etching? So, a big cavity would also tend to etch outward more quickly?
Barry Miller October 27, 2009 07:00PMHelpful info. or irrelevant? http://www.minsocam.org/MSA/Special/Pig/PIG_CQ/PIGQA_Rose.pdf
Dominik Schläfli October 27, 2009 08:51PMdissolution of a hoppered crystal could produce unexpected forms
photos of pristine galena from the same location show some hollows in crystals
could be some intermediary stage of dissolution. while still manufacturable, the inclusion of the large steps in the hoppered face is more complicated to realise and hints at a certain level of sophistication. The galena on the left looks quite natural.
Stepped faces are found there:
Jolyon & Katya Ralph November 02, 2009 12:56AMI've just come back from Munich where I haad an opportunity to look at a lot of specimens close-up, including some of these skeletal galenas and also a lot more pieces of different forms of galena from the same deposit.
I also got to talk to a few people about these unusual shapes to get opinions on whether they could have a natural origin, and between us we were able to postulate some vague yet plausible reason that could explain why small cubes and large cubes both ended up with frameworks of a similar thickness, seemingly impossible. Basically, imagine galena cubes growing, and during final growth phase, chemistry changes a little (maybe a little more/less Ag, or something else). Then conditions change and the galena is etched away, but the final stage which would be a layer of similar thickness on all cubes, is more resistant. If the crystals were hopper crystals to begin with, it could explain very easily how these skeletal cubes came about.
Having spent quite some time on this during the Munich show, I have to say I am changing my view now, and I'm more convinced now that they are genuinely natural phenomena. They are certainly worthy of some decent research however to identify the method of formation, because they're unusual!
I also spoke to one of the main bulgarian dealers who handles these things, who wants to send photos that will help convince people they are natural. I also took some photos myself of galenas at the show, on some of the pieces normal galena shows some of the strange stepped patterns we saw in the skeletal cubes and we thought might be because of abrasion loosening particles along lines of cleavage. On closer examination it looks very much more like a growth feature (or an etching/recrystallization feature) than anything physical.
So... if you were about to throw out your skeletal galenas in disgust, wait a moment, they're probably fine after all!
ps. of course, the story is far from over. More research is needed, they are fascinating things.
Andrew Tuma November 02, 2009 02:55AMJolyon, really good investigative comments,
I didn't want to say too much during the early discussion as I have not had the opportunity to see one in real life - one of the pleasures of living at the ends of the earth, but I am always careful to discredit an occurrence without investigation. Lets accept that one of geological/mineralogical situations do occur, how many minerals are currently found only in one location??
Sadly, we now live in a world where there are many people trying to fraudulently remove money from the pockets of naive "rich" people from economically developed nations. Fakes, being of natural history, cultural, atistic etc are one of the many methods used by occupants in underdeveloped countries to "fleece" the unsuspecting.
The result is that any specimen that has unusual color, habitat, associations etc tends to be immediately viewed as a fake, without extensive research to verify these claims. I always thought that we allowed innocence before proving guilt, appears not in these cases - though one has to admit to a fair bit of previous "form" from these countries.
A am sure that if Tasmania was in an eastern european, asian country, etc, some of the minerals specimens we see from the west of Tasmania would also be questioned...
Lets keep an open mind and do the investigations, otherwise we may miss the pleasure of something very rare or unusual due to our cynicism.
Marcus Grossmann November 04, 2009 07:28PMInteresting discussion.
By all respect for Rock Currier I can definitely not agree with his arguments.
It is no argument if somebody claims that he knows somebody who knows somebody who knows somebody with a sandblasting machine and that is the fact that the galenas must be fakes.
I know nobody with a sandblasting machine, but I have several skelettal galenas in my private collection. And most of these specimens consist of several attached skelettal crystals, you can never cast by sandblasting. All the edges of my specimens do not have round faces, but stepped faces, which you also can never cast by sandblasting in my opinion.
And to the end, there are small tiny quartz crstals on some of these edges, which you destroy immediately by sandblasting.
To make a long story short - these facts convince me so far, that at least my skelettal galenas are not man made.
Rob Woodside November 04, 2009 08:20PMMarcus, Rock actually made one from a Tristate galena, so this is not hearsay. If you were more familar with airblasting, you would know that it can be very accurately directed thus preserving the edges and any quartz xls that might have grown there. Why are there none of these quartz xls on the cavernous parts of the galena? What I find troubling are the cleavage steps that are evident in the photos. If there were other species growing in the cavernous regions then you would have proof that these are not fabricated. As with the stringy Ag wires that can occur naturally or be lab grown, these galenas might be real or air blasted. I think the question hinges on whether the cavernous regions show cleavage steps or xl faces. A good photomicrograph should tell the tale.
Jolyon & Katya Ralph November 04, 2009 09:47PMRob.
As you know from my earlier messages I was pretty convinced before I went to Munich that these things must be fakes. But having looked more at samples of these and other specimens, I don't think the stepped effect was caused by cleavage but is a growth pattern. I think these things have had multiple periods of growth, selective dissolution and regrowth, which is why you see some other specimens from this area that look like 'melted' galenas. I saw a small 20 euro specimen of normal crystalline galena at Munich from the bulgarian mines, and on the back was an area that looked like it had been melted and showed the characteristic stepped effect you see in the skeletal crystals. Here's a photo of it
There's no way this piece was sandblasted, so I have to accept the stepped patterns in the galenas are almost certainly natural. And if that is natural, then it makes it far more likely that these skeletal galenas are also natural.
Edited 1 time(s). Last edit at 11/04/2009 09:52PM by Jolyon Ralph.
Rob Woodside November 04, 2009 10:00PMThanks Jolyon. Not having any examples myself I should probably keep my mouth shut and my mind open. The only melted galena I'm familiar with are the rare Nanasivik pieces, none of which showed the cleavages or growth features. I hope you were able to afford that piece or at least get a photo of it. Until there is found some other mineral overgrowing the caverous regions or a photomicrograph shows xl faces from dissolution, I'll maintain my doubts. There is still the possibilty that some are real and some fabricated. It would be interesting to compare photomicrograghs of what Rock created and a purported real one.
Roger Lang November 04, 2009 11:01PMHi all,
glad that Jol posted his comment(s) .. and also glad that my old school understanding of precipitation/dissloution etc. in hydrothermal systems doesn´t seem to be that wrong - as i wrote earlier the composition of solutions/saturation/temperature etc may affect already crystallized individues in strange ways ... maybe our thermodynamic cracks here can explain the selective solution of faces and edges more sophisticated. But i am still waiting for Rock´s picture of a hand-crafted specimen of that kind. I would consider this very interesting although i am still convinced (and after Jols comments much more) that these Madan specs are natural. Regarding the sand-blasting: IMHO one could only save quartz etc. with baking soda or dolomite abrasive .. with glass (beads) or quartz it would be very hard to selectively blast such parageneses.
BTW Jol, hope you had a good time and good beer in Munich,
Ryan L. Bowling November 07, 2009 02:51PMJolyon,
I saw in the Munich report, that because there are quartz crystals inside the galena crystals, you are leaning toward the fact that they are real. I am not a deposition expert, but the galenas were deposited secondary to the quartz crystals in the pocket.
With that said, it is really quite easy to remove galena, without damaging the quartz crystals inside. As Rock described in his air abrasion technique, this is quite a simple process.
This is a good discussion thread.
James McGuire November 07, 2009 04:41PMI don't have one of these Madan "reverse-skeletal" form galenas, and they apparently do not exist from any other site in the world. I have only paid attention to pictures of them, but remain unconvinced. Are there any conclusively could not have been "manufactured" via air abrasion? This might include (1) minerals growing on top of the skeletal galena (not underneath the galena, as Ryan noted); (2) very small skeletal galenas that could not be the result of air abrasion techniques (there must be such a size limit); (3) galenas in small cavities where it would be impossible/impractical to air abrade them; or (4) galenas collected in situ in the "reverse skeletal" form. Others have hinted that they might have specimens that could not have been faked. I would be quite interested to see some of these.
Also, regarding the theory that these are partially dissolved hopper-growth crystals: is it not still a stretch to call upon what is described as a growth phenomenon (the "stepped" galena crystal) to explain a morphology which is theorized to be the result of dissolution processes?
Joseph Polityka November 07, 2009 05:04PMHello,
This is another interesting discussion on MINDAT.
I think we should watch out for a continuing supply appearing on the market. If this is a one time find, not many will be coming on the market in the future unless they are being hoarded. Jolyon's photo of a specimen featured at the Munich show, which had quartz crystals growing inside a cavity, is positive evidence that these coud be real. If a specimen comes on the market with a fragile mineral like calcite, barite, etc. growing in a cavity, then that would be absolute proof that they are genuine.
Matt Neuzil November 07, 2009 05:28PMwell while there are ways to have "proof" I think any absolute proof would only come in a video of the discover. Without it we are only lead to believe that this old, one time find is real. There is proof and then there is proof.
A buena hambre no hay pan duro
Ryan L. Bowling November 07, 2009 05:38PMJames,
I assure you this, as I can tell you it can be done. Here is a photo of a galena from the Blanchard Mine in New Mexico, great etching patterns, done in 10 minutes.
Joe, you make a good point about softer minerals inside the cavity, although I have yet to see this occurance.
Here is an example that I have an issue with, if there is solution etching in the pocket or distorted growth, why do some of these galena crystals on the piece have little distortion?
Edited 2 time(s). Last edit at 11/07/2009 05:43PM by Ryan L. Bowling.
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Jolyon & Katya Ralph November 07, 2009 06:06PMOk Ryan,
Thanks for taking the time to do the experiment - this is exactly what we needed to see - proof that similar material can be created artificially.
While it's impossible to say for certain right now, your experiment has swung things firmly back towards the possibility that they are faked.
What an exciting thread this is turning out to be.
Rob Woodside November 07, 2009 07:18PMRyan, I love your first photo with the inserted quartz xl that proves these are real!!! The next step is to insert one with non fluorescent glue!!! Your observation of the paragenesis in your earlier post is quite telling. Now I am more puzzled by Joyon's photo than these cavernous Galenas, but I suspect the luck of a fracture produced it.
Rob Woodside November 07, 2009 07:39PMGood point Dominik. Ryan please replace the quartz xl with a calcite crystal, then it will be real. As with my allusion to non flourescent glues, the danger here, as with any fakes, is that once the faker knows of an objection specimens will appear that meet the objection. I think these are great mineral art!!!
Edited 1 time(s). Last edit at 11/07/2009 07:40PM by Rob Woodside.
Ryan L. Bowling November 07, 2009 08:15PMRob,
I did not insert any quartz crystal in any of the photos, I think that what you see is the hollowing out of the crystal, or your comment is in jest. The matrix is classic Blanchard Mine quartz crystals.
Edited 1 time(s). Last edit at 11/07/2009 08:46PM by Ryan L. Bowling.
Rob Woodside November 07, 2009 08:47PMSorry Ryan, I got the impression from your posting and photos that the quartz xl in the first had been inserted in a xl of your second photo. In the absence of any soft xl overgrowing the caverns, one has to look at photomicrographs to see if these are cleavages or dissolution features.
edit. The first two photos look like Banchard material and thinking the quartz was inserted the fakery seemed obvious and when that happens I get sarcastic. At least your experiment vitiated the claim than any quartz would be blown away in the cavities. Until something soft is found in the Bulgarian cavities, one could assume that the paragenesis was Galena, quartz, dissolution. Still the difference between cleavage and dissolution should be obvious under the scope.
Edited 1 time(s). Last edit at 11/07/2009 08:56PM by Rob Woodside.
Robert Rothenberg November 08, 2009 01:28PMI have been following this thread with interest having seen some of these at Springfield. Jolyon's photo reminded me of some micro specimens I have in my collection. These are from Cornwall, England, and date back to at least the late 1800's (having been part of John Frederick Calvert's collection - he died in 1897). The crystals are about 3 mm, and the material associated is Sphalerite (no photo) and Baryte. In DSCN 6136, the Baryte is visible on the side. It is in perfect condition - no scratches, etc. I suppose something harder than Galens and softer than Baryte could have been used to abrade the crystals, but it seems bizarre to do so with micro material.
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Bri Dragonne November 08, 2009 02:13PMBob:
I think one of the differences between your specimens and the skeletal Galena is that there is a more rounded form to your specimens than what I have seen so far with the skeletal Galena.
Your specimens just look 'Right'.
I think if we got quite good shots of the stepping patterns in the skeletal Galena, it would show that the 'steps' are actually of a much more ragged appearance than your specimens.
John Betts November 09, 2009 06:19PMI believe the faked galenas are easily identified with a good microscope. The skeletal crystals that have been microabraded very clearly show rounded, dull surfaces the result of abrasive action. The genuine (I believe) show distinct growth-layers that are sharp and well defined.
Steve Hardinger November 09, 2009 06:27PMOne idea that seems to be absent from this thread is this: just because the appearance of these galenas can be mimicked by man (or woman or air blaster) does not mean the Bulgarian specimens are or are not fakes. Metaphor: I can grow diamonds in the lab, so all 'natural' diamonds are fakes?
Because no one I know of has the photographic equipment (or lifetime) to actually observe the galena growth or etching it situ, I believe the most definitive evidence will be a photo of the specimens in question in situ.
Until such a photo surfaces, I'm inclined to believe these specimens to be fakes. And I suspect because we've shown the world how easily they can be made, they will appear in quantity at Tucson, perhaps with a Chinese locality label.
Rob Woodside November 09, 2009 09:00PMSteve, as I pointed out earlier in this thread some of these galenas may be real and some faked, like the stringy wire silvers. As I and others have pointed out, a good microscope will tell if the lines in the galena are due to growth or cleavage. An in situ photo can be easily faked by mere careful placement of well carved galenas. Air abrasion will not produce micros and the remnants of growth hillocks. The presence of bas relief or the presence of soft minerals in the caverns would prove reality as well as. The fact that none of the Bulgarian galenas show any bas relief should raise a lot of red flags.
I suspect the appearance of this thread will decrease the further appearance of such specimens giving credence to those who claimed this is an old one time find.
Alfredo Petrov November 12, 2009 03:02AMI agree, Reiner. That's one of the reasons I was first suspicious too. But Jolyon has come up with a possible mechanism to explain it: Imagine a hopper-faced galena that changed composition as it grew, with the older growth (the center of the crystal) being less resistant to dissolution than the younger growth (the skeletal edges). This might be theoretically possible, but personally I'm still skeptical. I'll believe in the natural origin when I see one that has its "tunnel" entrances blocked by quartz or other minerals making it difficult to point a microabrasive pen through it, or a specimen with younger and softer minerals growing in the cavities, but I'm trying to keep an open mind (although a friend told me our brains will fall out if our minds are too open). :)
Reiner Mielke November 12, 2009 03:42PMI cannot understand the concept of "older" and "younger" when it comes to skeltal growth, only slower and faster. Seems to me that the more rapidly growing edges would also be the least stable and more likely to dissolve than the slower growing centre.
Alfredo Petrov November 12, 2009 04:39PMThe crystal starts growing from a point, so that's the oldest part, now in the center (currently vanished on the Madan specimens). Material added to the exterior is of necessity later (younger). This is complicated if different stages of growth had different compositions. Although theoretically the composition is just PbS, traces of other elements can distort the structure - like Sb, Ag, Tl, etc. - and that might result in different rates of dissolution in a compositionally zoned hopper crystal. Hypothetical. Maybe there are already studies of trace element variation during growth of Madan galenas? (Note that I'm not suggesting this is what actually happened, just presenting one possibility about how the observed crystal habit could have come about naturally if these things ever get shown to be natural, for which no evidence has yet been presented.)
Edited 1 time(s). Last edit at 11/12/2009 04:40PM by Alfredo Petrov.
Ken Doxsee November 12, 2009 05:25PMThrowing another thought into the fray --- might not screw dislocations, evidenced by spiral features on crystal surfaces, lead to preferential dissolution of material from the spirals rather than the edges of the cube. If we look at "normal" galena crystals from the area, are screw dislocations common?? --Ken
James McGuire November 12, 2009 05:33PMAlfredo Petrov Wrote:
> The crystal starts growing from a point, so that's
> the oldest part, now in the center (currently
> vanished on the Madan specimens). Material added
> to the exterior is of necessity later (younger).
> This is complicated if different stages of growth
> had different compositions. Although theoretically
> the composition is just PbS, traces of other
> elements can distort the structure - like Sb, Ag,
> Tl, etc. - and that might result in different
> rates of dissolution in a compositionally zoned
> hopper crystal. Hypothetical. Maybe there are
> already studies of trace element variation during
> growth of Madan galenas? (Note that I'm not
> suggesting this is what actually happened, just
> presenting one possibility about how the observed
> crystal habit could have come about naturally if
> these things ever get shown to be natural, for
> which no evidence has yet been presented.)
The Madan galenas linked earlier in this thread all have voids at the center. Wouldn't the oldest part of the crystal need to nucleate on something? It seems very unlikely that the center represents the oldest part of these galena crystals.
Rob Woodside November 12, 2009 06:37PMKen, I'm not sure what sprial features you are referring to. Dislocations can usually only be seen on the atomic level.
So James, since "It seems very unlikely that the center represents the oldest part of these galena crystals", how do you think these xls started, independently at the same time exactly a whole number of atoms apart, from 8 corners or 12 edges or some combination, all cm apart???
Edited 1 time(s). Last edit at 11/12/2009 06:39PM by Rob Woodside.
Rob Woodside November 12, 2009 07:18PMFair enough, I haven't seen one either. Crystal growth is still a black art. I find the skeletal mm sized gold octos from Eagles Nest puzzling. Occasionally one is quite equant, but there is a lot of associated parallel growth. When galena grows fast (presumably) there is usually herring bone dendrites and these skeletel things are only known from Medan.
Edited 1 time(s). Last edit at 11/12/2009 07:24PM by Rob Woodside.
Reiner Mielke November 12, 2009 07:29PMI still see no reason why older parts should be more easily dissolved than younger parts, unless there was some compositional variation with time that made the older parts more soluble, which I guess is possible. Seems to me that one assumption is that the younger stuff is insoluble rather than just less soluble. That to me seems unlikely since experiments on solubility of Galena do not indicate that impurities are an important factor in solubility ( at least that aspect seems to have been ignored by researchers so I am assuming it is not significant).
As such, I would expect to at least see some rounding of the corners and edges, which I do not see in the samples in question. Of course I guess one could argue that the situation then reversed itself and the sharp edges and corners represent a new period of hopper growth. These crystals would ceratinly make an interesting study for some graduate student. However, it wouldn't surprise me if we started to see similiar stuff coming out of China or Poland soon, or is this stuff already coming out of Poland? 8-) Come to think of it, the possibilities are endless, hollow calcite crystals would be cool! How about hollow apophyllite crystals from India ( damn now I've given them an idea on what to do with all their apophyllite).:D
Rob Woodside November 12, 2009 08:02PMThanks Ken, The 10-3 and even the 10-6 m ones pictured there are unusual. I haven't yet seen any such evidence on these Medan pieces. Photomicrographs would be welcome.
Reiner, now we'll know who to blame if such mineral art starts showing up!!! I think it was Steno's second law from the 17th century that surfaces with the largest area grew the slowest. The exsolved fluorite corners I think are supposed to reflect a time dependant compositional growth, that might indicate the cube faces filled in last. However I think your suggestion that impurities to inhibited the dissolution preferentially attached to the corners makes more sense.My objection was that all xls start from a single pointlike region so the central material is the earliest. If the central material is absent then it was either carved or dissolved out. The skeletal gold octos all have a central region.
Dominik Schläfli November 12, 2009 09:31PMInstead of positing compositional variations, the absence of center could be explained if the skeletal growth resulted in the final layers on the cube edges reaching a much greater thickness than the centers. Undissolved skeletal galena from the area shows some candidates:
some appear to have deep hollows:
This one is intriguing
the back side shows a hollow cube not far from a pristine cuboctahedron. This is almost like double crossing in espionnage:
- a naive diligent manufacturer would not have left a single crystal untreated
- a naive careless manufacturer could have let it slip
- a smart manufacturer would have left the cuboctahedron there, as it is not unusual in nature for conditions to vary across short distances, as evidenced by the difference in habit.
Reiner Mielke November 12, 2009 09:36PMGot this from Wikipedia so not sure how correct it is but:
Rate of dissolution
The rate of dissolution depends on:
• nature of the solvent and solute
• temperature (and to a small degree pressure)
• degree of undersaturation
• presence of mixing
• interfacial surface area
• presence of inhibitors (e.g., a substance absorbed on the surface).
The rate of dissolution can be often expressed by the equation of the form:
where: dm/dt = A*D/d *( Cs - Cb )
m - amount of dissolved material, kg
t - time, seconds
A - surface area of the interface between the dissolving substance and the solvent, m2
D - diffusion coefficient, m2/s
d - thickness of the boundary layer of the solvent at the surface of the dissolving substance, m
Cs - concentration of the substance on the surface, kg/m3
Cb - concentration of the substance in the bulk of the solvent, kg/m3
For dissolution limited by diffusion, Cs is equal to the solubility of the substance.
The dissolution rate vary by orders of magnitude between different systems. Usually, substances exhibiting low solubility exhibit also low dissolution rates.
Seems to me that the surface of the edges and corners of a hopper crystal are greater than the center of the crystal, thus according to the equation the rate of dissolution should be greatest at the corners and edges shouldn't it?
Ken Doxsee November 12, 2009 09:41PMReiner - This is why I raised the issue of spiral growth features (or, more generally, defect-type structures on the surfaces) - these types of growth features and/or defect sites can represent relatively unstable sites of a crystal, and could potentially be more subject to dissolution than the more obvious corners and edges. The jury's still clearly out on these particular galenas, though, so don't assume I am convinced they are natural! --Ken
Dominik Schläfli November 12, 2009 09:47PMReiner, it's even worse than A) that if you consider the geometry and diffusion . The edges and vertices see a much larger portion of the solid angle, and transfer to and from the edges to the solvent occurs at a higher rate than for large flat surfaces or cavities. Thats also the driver for skeletal growth.
to illustrate: http://www.mindat.org/photo-64684.html
But if under certain conditions you can get pronounced skeletal growth, and under other conditions you can get more "spherical" growth, you could also imagine the same for dissolution: dissolution that would be the reverse of skeletal growth, and dissolution conditions that would be the reverse of spherical growth. If the crystal grew skeletal and dissolved spherical, you would not return neatly to the initial conditions.
This is just my intuition, nothing more.
Alfredo Petrov November 12, 2009 09:48PMJames wrote: "...the voids in the center of the Madan galenas do not seem to be the oldest part."
That's precisely the point of suspicion here, James. A cubic crystal would (generally) grow at similar speeds in all directions; fast growth on the edges leads to hopper-faced or skeletal crystals. The center, or close to it, was where growth started and that part is now missing. The remaining cavity is not a growth feature, it's a dissolution feature or a mechanical removal feature, depending on whether you follow the natural etching theory or the human fabrication theory. Either way, they most certainly didn't grow in the shape you see them today!
Bri Dragonne November 12, 2009 11:34PMIt would seem to be that the answer is likely 'And' :
I believe that there is natural material of this like AND fabricated ones.
One of the examples shown by Jolyon (Though it was later edited out with a different photo) looks right.
It may be that a few natural ones were found, sold for quite a lot of money and then came the 'Eureka!' moment where people saw the huge prices (Relative to the average Galena specimens from there) and decided that if a few natural ones were good, many more fabricated ones to sell at that price are even better.
When I look at the amounts being asked for ones that I still believe are fabricated (In terms of having the right look to them visually), it certainly does make it worth the time to make good forgeries of the original material.
This of course is just a scenario but one that I am thinking could be the correct one.
When relatively large amounts of money are involved, people can get awfully creative.
Reiner Mielke November 13, 2009 01:09AMHello Dominik,
If dissolution where simply the opposite of growth then one would have to say that a face would dissolve faster than the corners and edges. However, this is not reflected in the dissolution equation which suggests that such a simple relationship is not the case.
Dominik Schläfli November 13, 2009 05:24AMIt sure gets a bit more complicated with crystals because of the anisotropy but look at the following:
a crystal in equilibrium with the surrounding solution sees on average the same number of constituents entering the solution as depositing on the surface. Leaving the equilibrium, in one direction thereis growth, in the other there is dissolution.
Due to geometric and crystalographical effects, you could have an isolated crystal seeing net gain on some faces and net loss on others.
Ken Doxsee November 17, 2009 05:46PMOK, check out this specimen. I find it hard to believe that someone other than Mother Nature would deign to make such bizarre alterations! The link is to an auction site that will close in about 6 hours, so look quickly! --Ken
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