# Iridium, Lead or what?



## SilverA (Apr 16, 2012)

While metal detecting, I came across a round ingot of silvery metal (weighs about 5 kilograms).

At first I suspected it was silver so I took it to a couple of gold/silver buyers. Based on the acid test, one of them said it was silver and the other said the test was inconclusive. 

I also took it to a higher end gold buyer with a SpectroLab XRF. Those results showed insignificant amounts of Iridium and other precious metals (<0.0001%) and 1% Tin.

Still not satisfied, I took it to yet another gold buyer that performed an acid test (he thought it *may* be Platinum) and sent in my sample to their lab.

Almost four weeks later I got their results which said: 91% Ir, 7% Fe and 2% Zn. So far so good. Unfortunately they only buy Pt, not Ir.

Considering the amount I had found, I was really interested in selling it.

So I took another 150g from the main piece and sent it off to a PGM refinery expecting a decent sized check.

About four weeks later, I got a call from the owner and he tells me that what I had "claimed" is Iridium, is in fact Lead.

Something does not add up.

My question is, how is it possible to have such a large discrepancy across the different test results?

What type of test would show 91% Iridium when another test shows mostly Lead?

On a side note: In my research I've come across an interesting Iridium alloy named Chengdeite. One of the sources lists Ir3Fe as 91.17% Ir and 8.83% Fe. Anyone know what the melting point of this alloy might be?

Thanks for reading.


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## Lou (Apr 16, 2012)

Welcome to the forum.

It is assuredly NOT iridium. 

You're not going to find a 5 kg metal ingot of iridium. You'd have a hell of a time taking a 150 g chunk out of it too. If it scratches with a chisel, it's probably not iridium.

The results from that assay lab are about as good as Charmin. Even at the sintering temperature, your two percent zinc is long gone. One of the ways to purify iridium is by electron beam remelting. It's at the very fringe of what you can fuse with oxyhydrogen. If you sent it off to a PGM refinery here in the states, I'm sorry. JM is only paying about 70-80% of what it's worth right now, plus the lot treatment fee and all the rest. 


Your chengdeite sample (if indeed that) is worth many, many times the $1150/oz going price for iridium (in bulk, mind you). To say it is rare isn't even comparable to an understatement. 


I share your sentiment of something not adding up.


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## jeneje (Apr 16, 2012)

sounds like a snake in the wood pile somewhere and it has struck the money tree. :roll: 
good luck
Ken


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## butcher (Apr 17, 2012)

Lead is soft, and silver is hard.

How hard is the material in MOhs?

http://www.google.com/#sclient=psy-ab&hl=en&rlz=1R2RNQN_enUS457&q=ore+hardness+test&rlz=1R2RNQN_enUS457&oq=ore+hardness+test&aq=f&aqi=&aql=&gs_l=hp.12...11906l14578l2l18516l5l5l3l0l0l0l235l422l0j1j1l2l0.&psj=1&fp=1&biw=1024&bih=583&bav=on.2,or.r_gc.r_pw.,cf.osb&cad=b


What is its density or specific gravity?

http://www.google.com/#sclient=psy-ab&hl=en&rlz=1R2RNQN_enUS457&q=ore+density+specific+gravity+test.&oq=ore+density+specific+gravity+test.&aq=f&aqi=&aql=&gs_l=serp.12...4063l4063l2l5750l1l1l0l0l0l0l140l140l0j1l1l0.&psj=1&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=4511e698c622b6ec&biw=1024&bih=583




How does it react with a flame in a loop of Pt wire?

http://www.google.com/#sclient=psy-ab&hl=en&rlz=1R2RNQN_enUS457&q=ore+flame+color+test.&oq=ore+flame+color+test.&aq=f&aqi=q-w1&aql=&gs_l=serp.12..33i21.20234l38312l4l40844l7l7l1l0l0l3l485l1861l0j1j3j1j1l6l0.&psj=1&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=4511e698c622b6ec&biw=1024&bih=583

more:

http://www.scribd.com/doc/15247849/You-Can-Smelt-Too

I would not buy any material I could not identify what I was buying, others feel the same, unless they can prove to themselves as to what you have or the value of it, also it seems strange to find a specimen of elemental metal, it would be a very rare find, and a valuable metal chunk that large very strange, can you post a picture, of this material? 

It sounds to me you could have found a meteorite , or a rare specimen of ore, or else just someones trash, at this point it is hard to tell.

also be careful of them snakes they get you when your not paying attention to what your doing.


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## SilverA (Apr 18, 2012)

Lou said:


> Welcome to the forum.


Thank You.



Lou said:


> Your chengdeite sample (if indeed that) is worth many, many times the $1150/oz going price for iridium (in bulk, mind you). To say it is rare isn't even comparable to an understatement.


Just to clarify, what I should have said was "In my research I've come across *references to* an interesting Iridium alloy named Chengdeite". I just thought it was interesting how close the composition is to the metal I was told that I have.


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## SilverA (Apr 18, 2012)

butcher said:


> How hard is the material in MOhs?


I don't have a way to precisely measure this, but I do know it's softer than high-carbon steel and appears to be somewhat harder than copper.



butcher said:


> What is its density or specific gravity?


Again I'm not sure how precise this is, but based on the volume and weight, the density works out to ~13.12g/cm³.



butcher said:


> How does it react with a flame in a loop of Pt wire?


I wish I knew, I'm not set up to perform any flame or chemical tests.



butcher said:


> can you post a picture, of this material?


Gladly.

Top view:



Bottom view:



Side view:



Close up:


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## SilverA (Apr 18, 2012)

butcher said:


> It sounds to me you could have found a meteorite , or a rare specimen of ore, or else just someones trash, at this point it is hard to tell.


The closest in terms of properties seems to be Lead. However, I haven't been able to find out the exact properties of Iridium-Iron-Zinc.

And if this is Lead, what I would really like to know is, what caused the false positive?


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## Lou (Apr 19, 2012)

Incompetence knows no bounds.


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## freechemist (Apr 25, 2012)

Hi SilverA,

The density of Iridium is 22.56 g/cm3, the density of Chengdeite (Ir3Fe) is 19.3 g/cm3. Pure lead has a density of 11.3 g/cm3.

The melting point of pure lead (327oC)is very low, compared to other metals. Pure lead is very soft.

Large discrepancy across different test results may have different reasons, namely incompetence, like Lou mentions, inhomogeneity of your big,big nugget, what an individual gold buyer has in mind, inappropriate method of testing and/or sampling. A simple "XRF-shot" as an example is not an appropriate method and thus is prone to deliver entirely false results.

If you really want to know the composition of your metal-chunk, IMHO there exists only the hard and costly way to reveal it. Drill your chunk on several locations (upside, downside, center, left, right) to make holes of different deepness, collect all filings and put and mix them together and then divide the collected material into 2 or 3 exactly weighed samples. Send these individually to 2 or 3 different reknown labs, known to be able to deal competently and reliably with such materials (it has not necessarily to be a gold- or PGM-refinery, it can be also an university- or a government-lab) asking for determination of their exact chemical composition.

Good luck, freechemist


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## mls26cwru (Jul 11, 2012)

not sure how much help this will be, but you may have found an anode from a cathodic protection system...

http://en.wikipedia.org/wiki/Cathodic_protection

It looks an awful lot like the lead alloys my dad used to make cast bullets from, but as you can see from the charts, it could be a wide range of materials. you could try a simple plumbing torch to see if it melts... that would at least rule in/out relatively pure lead (watch out for any vapors though)

hope that was a little bit of help.


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## Lobby (Jul 11, 2012)

Many of the lower priced XRF's only have basic gold (and silver, with perhaps some PGM's) in their data sets. If your sample isn't in their database, or more accurately, if your sample isn't similar in composition to the various datasets it has, the results are worthless.

Absolutely worthless.

I'd cut a piece off.
- measure it's density
- try to melt it with a torch

I also suggest stopping the daydreams of hitting a jackpot. If it were me... :mrgreen:


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