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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?
May 10, 2010 03:32AM
    
Rock, could you please post closeup pictures?

Thanks
Bob


Rock Currier Wrote:
-------------------------------------------------------
> I 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.
Re: Have the reverse-skeletal Madan galenas been faked?
May 10, 2010 10:08AM
    
The past year new"man made "fluorite scepters"are beeing sold from Erongo mad eby the locals by sanding away parts of the specimens! I ahve seen western dealers selling such for raher big money! SO beware!!!
Re: Have the reverse-skeletal Madan galenas been faked?
May 10, 2010 05:37PM
Hello everyone,

As just a casual observer of this discussion I have been pretty interested in the discussion taking place. In my own research I have made in my lab completely hollow mm sized pyromorphite crystals and it is possible to make the same with chlorapatite as well. But that is a different system with different issues. Mainly I saw Jolyon post "ps. If anyone does want to buy one now is probably the best time - with the uncertainty the dealers can't price them as high as they probably are worth. But it's a gamble, if they're proven genuine, value will skyrocket for sure. " So I said heck I will search for some on google and stumbled across a paper on Madan Galenas with fluid inclusions from 1977.

I.K. Bonev Mineral Deposita (Berl.) 12, 64 - 76 (1977)

(link)

In it they have detailed SEM investigation of the surfaces of galenas where reverse crystal impressions are observed forming from fluid inclusions. They state these can be casually observed by the unaided eye. These could be the "abrasion pits" mentioned in earlier posts.There is also description of the parallel lined curved surface sculpture. I am not taking a side on this. I have no vested interest in one way or the other. Just a mineralogical curiosity for me. I do however think this paper could aid significantly in this discussion since they have a detailed study of how these reverse crystal structures form.

-Harris
avatar Re: Have the reverse-skeletal Madan galenas been faked?
May 10, 2010 06:59PM
    
Thanks Harris, that is an interesting paper. Could you please email me a copy of the full article?
rwmw@telus.net
Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 03:33AM
Here are pictures of my example from this find. In the first picture you can see bits of chalcopyrite along some ridges and other mineralization along an inner ridge. This could only occur by either A) being artfully placed there after sandblasting (but why, and I see no evidence of glue), B. grew there naturally after natural skeletal growth of the galena, or C) the minerals were included within the Galena and exposed after sandblasting. I think the best answer is B, the minerals are on different "contour lines" of the Galena and would have had to be random inclusions within the Galena, which I think is unlikely.

The second photo shows small pyrite lined vugs exposed within the Galena - if the crystal was sandblasted, those vugs would also show abrasion, and they do not.

Last photo shows some quartz crystals. They do not show abrasion, but sandblasting could have been done by softer material than Quartz. For reference, Galena is 3cm across in size.

Thoughts?
Attachments:
open | download - g5.jpg (66.2 KB)
open | download - g6.jpg (65.3 KB)
open | download - g7.jpg (54.1 KB)
Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 03:34AM
Some more photos of specimen
Attachments:
open | download - g1.jpg (59.6 KB)
open | download - g2.jpg (55 KB)
open | download - g3.jpg (61.3 KB)
avatar Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 06:38AM
    
Mike,
thanks for posting the pictures. Based on those the specimens could be natural - or manmade. Pyrite is so much harder than galena so one could imagine that a softer abrasive would not affect those. One might also ask why a natural process creating the dissolution patterns in the galena did not affect the pyrites...
Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 07:03AM
Thanks for the clear photos!
Air abrasive units commonly use microscopic glass beads (hardness 5), looks like powder to the unaided eye, not quartz sand, so "sandblasting" is a bit misleading. Glass microbeads do not abrade pyrite or quartz. The photos show what one would expect if air abrasive had been used: galena deeply eroded; chalcopyrite abraded but slightly protruding from the galena surface because it's a bit harder than the galena; pyrite and quartz unaffected. This is not to say that your piece was made that way, Mike, merely that it could have been done that way.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 11:48AM
Very interesting photos!

On the one hand, photo G2 is very interesting, it seems to show two depressions on one surface of the crystal and one on the other. Any previous theories that I could just about accept about how these could have formed are somewhat blown out of the water by this, And it looks sculpted, it very much looks air-abraded.

However....

Photo G7 shows a very sharp edge to the depression in the top left corner, not a rounded blob depression as you see in other photos, I find it much harder to see how this particular depression could have been made by an air-abrader.

I love the fact these are so confusing. Perhaps there are some natural depressions in these crystals and they have been "improved" with an air-abrader to make them more valuable?

Jolyon
Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 02:00PM
Alfredo,

How do you explain the minerals at different "depths" on the surface of the Galena (i.e. on the right central ridge in photo G5)? Inclusions within the Galena that were exposed from air abrasion?
Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 03:28PM
    
Hi,

My two cents worth: they might be real, and if they are, they are not worth the high prices being asked. These are not cavernous gold crystals, are they? Contemporary specimens of galena are galena, period. If they were high quality specimens from a defunct, classic locality then the price would be no object.

I would be interested in hearing from the miner or person that was closest to the source when the specimens were found. Who are those people?

By the way, I hope they are genuine.

Best wishes,

Joe
Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 05:29PM
Yes, if you look at polished ore sections, you more often than not see complex networks of inclusions. Metallic inclusions at different depths in other metallic minerals are just as common as nonmetallic minerals included in quartz, etc. Not a surprise; you just don't see them normally because of the opacity.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
May 13, 2010 05:53PM
This is getting interesting. There seems to be a few more people on the man-enhanced side that the real though. I tend to believe they are man-enhanced over all but could it be possible that there were some natural crystal at one time but because of the high prices some creative soul decided "I can make these". Money does bring out the creative process. The ones that seem the most likely to be fakes are the ones that are etched all the way through. I just can't imagine a natural process that could leave the outside almost untouched and eat all the way through. Ones that are more of an indentation remind me of a hopper growth and have then under gone some sort of natural etching. I am leery of that but it is and idea. The main point of suspicion for me is that they have not been seen insitu and their origin seems to be vague. Oh well more fuel to the fire.
Re: Have the reverse-skeletal Madan galenas been faked?
May 14, 2010 02:51AM
Thanks for the information Alfredo,

Mike
Re: Have the reverse-skeletal Madan galenas been faked?
May 14, 2010 01:54PM
Very interesting thread.
I don't have any dog in this fight - I neither collect nor sell any kind of galena.
However, as one who used to operate a glass bead blaster in a small factory, I believe that it is somewhat misleading to simply state that glass beads have a hardness of 5, and therefore would not abrade anything with a hardness over that number. Because of the velocity of the beads, there is wiggle room. This is just based on my feeling from my limited experience with the equipment. I believe a similar effect is used in lapidary when an abrasive powder that is softer than the stone being cut is used for the final polish. In this case, I believe it is the pressure on the lap that allows softer powder to abrade. Anyone agree or disagree?
I'd like to see someone test the bead blaster on some of the associated minerals - to see if they are indeed untouched when the rate and time required to abrade the holes in the galena is applied.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
May 14, 2010 02:38PM
You can have a variety of different abrasive powders and you can of course vary the pressure - I have no doubt there are combinations that can successfully abrade the galena without touching quartz.

Jolyon
Re: Have the reverse-skeletal Madan galenas been faked?
May 14, 2010 02:54PM
Certainly without touching quartz - but without touching pyrite or especially chalcopyrite? I'm picturing the product, pressure, volume, and time required to significantly abrade galena. I'm just wondering if this operation would affect the associated minerals. I don't think it's a simple as saying "the abrasive medium is softer than mineral X, so it won't be abraded."
I've never seen any of these specimens in person. I'm highly skeptical that they are natural. I'm just pointing out that further investigation into the effects of abrasion on associated minerals may be warranted.
avatar Re: Have the reverse-skeletal Madan galenas been faked?
May 14, 2010 09:42PM
Certainly there is plenty of "wiggle" room for glass beads to effect and abrade harder materials. A lot depends on the velocity with the glass beads impact the surface of the material. Although glass beads at about 60 psi entrained in an gas stream will usually not produce any visible change to Quartz, it will have some effect on the Quartz. After subjecting the quartz to glass beads at 60 psi. and placing the quartz in HF for a while, it is evident that the bead blasted surface will etch much more quickly than the unblasted surfaces. Glass beads at 60 psi will also not produce visible effects on the surfaces of shiny pyrite crystals but will eat up similar chalcopyrite crystals very quickly. Glass beads are commonly used to remove chalcopyrite from around Russian Sperrylite crystals. Also frequently the glass beads used to clean minerals are used many times over and often contains quartz fragments and fragments of other minerals that were removed from other minerals cleaned previously. This kind of "impure" glass beads can abrade quartz and tourmaline etc if you are not careful.

High pressure water is a very effective cutting media for concrete and granite. Diamond photographic needles are certainly worn away by soft plastic records over time. There is a lot about "hardness" that is not well known.

Rock Currier
Crystals not pistols.
Re: Have the reverse-skeletal Madan galenas been faked?
May 15, 2010 05:22AM
No one claimed that the chalcopyrite was not affected by glass beads, it would certainly be abraded, but less rapidly than the surrounding galena, which leaves the chalcopyrite standing out a bit. Yes, the surfaces of hard minerals can be damaged by percussion of softer objects (Yes, you can knock flakes of flint off with a piece of bone too), so it is up to the operator to choose a pressure and medium which will remove the undesired material and keep the desired material undamaged - easy enough when the hardness difference is as striking as galena and quartz.

Don't forget that these tools are more frequently used by fossil preparers than by mineral folk, and the fossil people are working on tiny details and materials of much smaller hardness difference - It is by no means the brutal clumsy tool that some of us seem to think.

But Rock's comment about etching after blasting brings up an interesting potential experimental procedure: Check the relative speed of etching (with ammonium bifluoride?) of a quartz crystal from inside a galena cavity with a (presumably unabraded) quartz from outside a galena cavity, on the same specimen. If sufficient blasting pressure had been used, one would expect the quartz from inside a cavity to get more etched. (Might not be definitive though if blasted at low enough pressure?)
avatar Re: Have the reverse-skeletal Madan galenas been faked?
May 15, 2010 08:20AM
    
This is NOT skeletal growth. Alfredo pointed this out earlier. Skeletal growth, like normal growth, starts from a nucleus and proceeds in all three dimensions (although the rate of growth may be different in each dimension, depending on the mineral studied and anisotropy effects of the medium in which they grow). Skeletela growth of galena is well known, but produces entirely different shapes. There is an article on the web showing this:

[www.geology.bas.bg]

What we see here are forms with a missing core. Name them as you like ("frames" seems to be appropriate), but don't call them skeletal. If they were grown like this, where did it start ? Irrespective of where the nuclei were initially located, a convincing mechanism needs to be found that alters the growth rate along the two directions of the three spatial axes. Otherwise, the growth would not have stopped at the corners !

The only way they could have formed naturally is by an etching mechanism.
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