FMF - Friends of Minerals Forum, discussion and message board

[nurbo]

Hello,
Has anyone seen these kind of dimples in Malachite before? Any ideas on how they form?

[arturo shaw]

Hi,

I have always imagined they form upside-down like stalactites and then got covered by the malachite growing outwards. I hope the experts can confirm that or give another explanation. Interesting question. Thanks for posting it.

Cheers!

Arturo

[Roger Warin]

Hi,
I think they are not dimples but the termination of small channels through which flow the aqueous copper bicarbonate solutions. So these are stalactites. Crystallization of malachite occurs in this outlet.
Roger.

[lluis]

Hi, Nurbo

I always thought what Arturo and Roger said: the end of channels

On the other side, could be a darker explanation. Some time ago (maybe three years), Bernard Ottens adverted collectors that in Congo, someone/s were done excellent repros/fakes of malachite stalagmites. Discovered by himself when one fell down, got broken and the mess of modern material (used as filler) was shown.

Aspect was identical to a legit stalagmite, so....

That was explained in Lapis (in german), but as far as I am aware, not in Mineralogical record.
The history is in the spanish forum (apart than in Lapis, I mean... :-) )
Maybe Jordi could help with link. I confess that I am absolutely two left handed when using the buttons of the forum... :-(

With best wishes

Lluís

[Jordi Fabre]

[lluis]

Thanks a lot, Jordi!

With best wishes

Lluís

[nurbo]

I don't think its a fake, here is a shot of the rear of the piece, there are some Quartz crystals in amongst the Limonite.

[Roger Warin]

Hi,
Of course this is not a fake. The craftsman cannot reproduce such a complex structure. In addition the outlets of small channels cannot so finely made with a drill. They are outlets flared by the effluent solution causing a mini-crater.
And the texture of natural crystallization is different from that of a mixture of grains.
Roger.

[lluis]

Hi, Roger, Nurbo

Roger, sorry for my bad english.
But the stalactites of malachite shown fakes by dropping down and breaking were so good that cheated Bernard Ottens, that is an expert and a dealer in minerals.
Is like to say that to cheat BM with a fake coin is easy.

They were crystallized, fibrous radiating crystals around the inner parts.
Channels as seen, although I think that are the exit of the water, could be also the result of crystallizing around an air bubble.

So, those ones, after the Ottens accident, well, we could believe, but we could not be sure, unless we were the ones who took the material from the wall, and being sure that was not added there.

Is more or less of what happens with magnificent Italian sulphurs crystallized from carbon disulphide. The article was published in Mineralogical Record.
I am pretty sure than mine is natural, for source. But after that, a real magnificent one, well, at least some museums did trials, And some showed traces of S2C.....

With best wishes

Lluís

[Roger Warin]

Hello,
The comparison with the sulfur dissolved in CS2 is not possible. It is a real solution of sulfur molecules, which can be quite concentrated and give a beautiful crystallization.
The time scale is not the same for malachite. Crystallization is made from ions: Cu2 + and (HCO3) -, plus the addition of hydroxyl groups (OH) -. Formally, it therefore takes a small chemical reaction.
There is another opportunity to see if the hole is natural or not. Just test its linearity. If bends are present, it is necessarily natural, but a straight channel can also be natural.
Roger

[lluis]

Hi, Roger

Well, maybe I am chemist and I see the troubles you say as not troubles,
Reactions are driven by concentrations of reagents and temperatures.
What nature can do, man can do (have you seen the reports on fakes in Lapis? Are interesting...)

Yes, the reactions in nature and the reactions in labo (well, in maker of stalactites), are not same. One is the precipitation of a basic carbonate of copper from a bicarbonate of copper (or just from a solution of copper basic carbonate) along time, and the other the precipitation/crystallization of a basic copper carbonate. That, my friend, is too similar to the crystallization of sulfur from carbon disulphide: carbon disulphide is the solvent for sulphur and ammonia carbonate is the solvent for malachite....

Rest, well, see if something odd is inside (that means crushing sample). Personally I would not do. But I would have probably it in purgatory during my collection...

Others are happy with the golds from Icaburu, the heliodors from Tadjikistan and so...
Why not?

With best wishes

Lluís

P.D.: By the way, bends could be also naturally artificial,,,,,

[Jean Sendero]

I cannot believe that I decided to get dragged into this, is it fake or not? Why are people so skeptical when they see something they cannot explain or understand.

First of all, and this was mentioned before I believe, but channels or chimneys in the center of stalactites are very common in a wide range of other mineral species (calcite, marcasite, goethite, mottramite, etc.... name it.). I own examples for all of these and no fake here.

For the malachite from the DRC, I was fortunate to visit with the mine geologist the "Mine de l'Etoile" in Lumbumbashi a few years back. During one of the visits, the miners showed me a huge cavity or karst (1.5 to 2 meters high), filed with malachite, bottryoidal, and stalactites (growing from top to bottom). Harvesting had started by the time i got there so it was very interesting to see how the guys are harvesting these malachite stalactites (doigt de femmes). And guess what......most had an empty channel, chimney in the center. So, are these fake too?

Nurbo, your stuff is as real as it gets. Nice piece by the way. Interesting matrix if it contains quartz. Not common in the host rocks.

Cheers

jean

[Jean Sendero]

Nurbo,

I omitted to reply to your two questions, so:

1) Yes I have seen those
2) No cannot explain how they were formed.

Cheers

Jean

[lluis]

Jean

As I said, a chimney in center is a must for a stalagtite.
But a chimney in one end does not assures it as legit.

And, if you wish to read the article of Bernard Ottens, maybe you could believe that there are fakes, that those fakes look like the legit ones. And that those fakes are very easily done.

I fear that some are like the defenders of the Black Sea Hoard in coins: a big rouse against the one that dared to say they were fakes. Even "proved" (ehemmm!!!!!) legit "scientifically"...
Just to be shown fake by a dealer who come from Bulgaria with repros bought from a museum, as repros of course, that matched the fakes....

But anyone is free to believe what he wills.
I prefer to be in the safe side... :-)

With best wishes

Lluís

[Jordi Fabre]

Lluís don't take it bad, but Jean is an experienced field geologist & collector, and if he saw in Congo this kind of Malachite I believe we should trust him.

Also, by my experience the faked ones are usually elongated, single (or few) stalactites and not clusters, short stalactites, and with an evident natural matrix in its rear, as the specimen from Nurbo. I could be wrong but...

[lluis]

Jordi, believe me, in question of opinions, I never take nothing bad.
Opinions are opinions.

I know that Jean is very well regarded (I trust in him, if that serves for anything).

But even thinking that the Nurbo stalactite is probably legit, it could be for what I know, fabricated.

Way to know by sure?
Break it.

And I would not do..

That said, I only placed what I think.
And as I said Jean could be very well the best. But Ottens was caught. And I think that no one questions Ottens...

With best wishes

Lluís

[nurbo]

These are the Quartz crystals I mentioned, they are to about 4 or 5 mm, well, I assume they are Quartz, maybe they are something else, the point being they wouldnt be there if it was a fake.or so I'm told.

[lluis]

Hi, Nurbo

With this photos, I think also it is a legit one.

By the way, in a fake matrix, all could be placed, depending of hability of "artist".

With best wishes

Lluís

[Roger Warin]

Hello,
I return to the subject of false malachite stalactites.
A first remark, the real are soft to the touch. There are no rough edges.
A careful examination shows an ordered structure. There is a repetition of small nipples of crystals resembling flower petals.
The section of the stalactite obviously has the hole in the supply channel. This radial feeding results from an accumulation of areas with oscillating colors, very dark green to light green.
False malachite stalactite is rough to the touch, as is made by projecting a jet of crushed crystals on a support. There is obviously then no organization of these broken crystals.
Roger.

[lluis]

Dear Mark

If Jordi gets the permission from Lapis, I think I could find the article on the fake malachites that Ottens published.

I fear that are not done with crushed crystals, as many fake geodes are done in Morocco.

They are crystals, and they look like natural ones.
Ottens was only aware of it when one crushed and show the "guts", showing it was no natural.

Are done precipitating malachite over the support, similar to making the fakes Italian sulphurs (other solvent, of course....)

Here is a link about one we talked in spanish forum:
https://www.foro-minerales.com/forum/viewtopic.php?p=28292#28292

With best wishes

Lluís