Please help estimating Au content for these

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hestati86

Member
Joined
May 13, 2017
Messages
19
Friends, though it's my first post here, I really need your help. I just discovered this board :roll:

We are trading e-waste in South East Asia, and recently we are getting many unpopulated, production scrap (pics attached on the bottom).

We need to offer our price for it, but it's tough for us to estimate the content. We're given the sample, but it's too small to do the actual test.

So, what I'm trying to do is get a very conservative estimation of Au content. Would you please quickly go through my estimations below? Do they make sense? Again, I can underpay for this material, so if I'm too conservative somewhere it's ok. I need to make sure I'm not too optimistic... Thanks!

Here's how I go about it:

1. 12 little rectangular boards per set, conservative assumption that each board is 10% gold plated on both sides. Weight of each set is 122g.

2. Each little board is 6.4cm by 4.4cm, therefore gold plated area is 6.4*4.4*0.1*2=5.632cm^2 of gold plating per little board or 5.632*12=67.58cm^2 of gold plating per set, including both sides.

3. Assume that this is class 00 (is it still the lowest?), so 20 micro inches thickness of the coating. In cm it gives me 0.0000508cm. Therefore volume is 67.58*0.0000508=0.00343cm^3. Since each cm^3 of gold is 19.3 grams, we have 0.0633 grams of gold per set.

4. Since each set is 122g and 1 ton is 1000000 grams, I have 1000000/122=8196 sets per ton. Therefore I have 8196*0.0633=519g of gold per ton of this material. To add a safety factor of 0.8, I get roughly 400 grams per ton.

2samiiv.jpg

15xa13r.jpg
 
Double check the gold itself and make sure that they are not engineering samples or production failures with a dusting of gold instead of the normal layer.
 
Thanks! these are in fact production failures OR terminated product. I doubt it is engineering sample, they have 2 tons of these. What do you mean by dusting? Any picture? To me, it looks ok layer of gold, definitely thin though. How thin would that dusting be?

Apart from this, do you agree that approx 10% is covered by gold on both sides?

Also, I'm wondering if there's software or maybe Photoshop plugin, where I load and it can tell me % of the color. Would be nice, anything with yellow is highlighted and % of the area is given.

Thanks again!
 
If they are production failures then you cannot assume the gold content can be calculated using the normal formula for gold thickness/surface area. That dusting literally can be dusting. GSP will probably be able to expand on this in a more coherent manner than me. I've run some of these and had very little return.

Not all are the same of course, I am just sharing my own experiences with these but I wouldn't pay more than a few hundred per tonne unless you are 100% convinced these have the full plating amount.

I hope that helps

Jon
 
It does help. I will try to do the lab test, even though I probably don't have enough. But to be honest, it looks like normal plating, not dust, but again I need to make sure.
 
Your estimation for plating thickness may be off by a factor of 10. Those pads are meant to be soldered to, so they will be ENIG plating. That can be as low as 2 to 5 micro inch thickness.

You can use some dilute Nitric acid to see the difference between ENIG and hard gold plating pretty easily. A drop of 35% nitric acid on hard gold plating just sits there and does nothing. ENIG is basically porous, so when looking through a microscope you will see a clear reaction happening as the Nitric acid attacks the Nickel and Copper 'through' the ENIG plating.
 
One of the main reasons such boards are rejected after an inspection is nonuniformity of plating.
Even if you take test samples you will find it hard to make a dent on a ton of material. so as to get a representative sample.
I would class it more as a copper recovery, then have a fire assay.
Take five to ten kilo's one board at a time, from equal point within the lot, Ash Smelt for copper.
Then test what you have.
That would give you a rough idea of content.
The bigger your random sampling the better idea you will have.
 
kernels said:
Your estimation for plating thickness may be off by a factor of 10. Those pads are meant to be soldered to, so they will be ENIG plating. That can be as low as 2 to 5 micro inch thickness.

You can use some dilute Nitric acid to see the difference between ENIG and hard gold plating pretty easily. A drop of 35% nitric acid on hard gold plating just sits there and does nothing. ENIG is basically porous, so when looking through a microscope you will see a clear reaction happening as the Nitric acid attacks the Nickel and Copper 'through' the ENIG plating.

Thanks! I didn't think about it. Though when I place it in acid, the flakes of gold are quite large, so this is definitely not dusting, but at the same time, I suppose that even 2 micro in can be in a form of flake, so yes... we will have to think what price to offer, maybe copper price... Thanks!

Edited... I made a mistake. It can be ENIG, it's not dusting.
 
Ash smelting for copper is a complete waste of time an effort. Don't waste your time doing it. Stupid advice.
 
anachronism said:
Ash smelting for copper is a complete waste of time an effort. Don't waste your time doing it. Stupid advice.
Rather Rude and inflammatory.
Pretty much underlines why I decided to walk away politely once I understood you better and reaffirms every day what a good decision that actually was.
Also, underlines our differing methodology.
I can not afford to gamble so test everything, metals, relationships, business models.
That is how I come to conclusions.
You do very well judging everything by eye, good on you. your clients do not ask questions why should I waste my time doing so.
Anyone can put out a silly lowball price and know they will always be in profit.
It takes a slightly differing proclivity to take an agreed upon fee in a transparent manner.
Or to accurately value a 1000 kilogram lot with only a 5-10 kilo test cross-section.
 
Ashing and smelting the copper is usually done on a larger scale than your sample and to do the smelting work just to assay the copper for PM's is not the approach I would use, still it is not stupid, but it wouldn't be my choice for a sample.

I would granulate the entire lot, take multiple samples from a well mixed pile of granulated boards, and digest the metals in Aqua regia. Multiple samples, a few ounces each tops. The granulating will expose any gold hidden in layers to the acid if you granulate to 1/8 to 1/4" size and multiple analyses will give you a range of concentrations. From that you figure what you are willing to pay for this material. If these boards are not high end boards, the aqua regia will need to be run on an AA to detect gold in the PPM range in the acid.

If the gold concentration warrants, and the lot is large enough, and you want to refine yourself, then ashing and a copper cell becomes an option if you take in the entire load. But remember, you pay on out-turn unless you properly sample the entire bulk batch that comes in.
 
I would love a granulator that could chew through a ton of boards at a time.
That would give you a very well mixed sample.
Sadly I have to gas off and ash before they will mill down.
Would not copper be the main cash cow followed by nickel and Au thus get the best return from a copper processor who pays out on trace impurities?
4Metals method would be the most effective way to estimate a content, but as the operational word is "Estimated" or in other words an approximate calculation or judgment of the value, number, quantity, or extent of something, that leaves the possibilities wide open.
There was no indication of how accurate an estimate was required so even judging by eye and weighing it in your hand would technically fall within the borders of this post.
Personally, I try to base my purchases on as concrete a set of numbers as I can. estimates especially other peoples tend to be affected by personal predispositions.
This is why such methodology have been eradicated from informed inquiry for several centuries.
 
With copper as the main cash cow, you need a large operation and efficient handling. and as much as it sounds like a wonderful concept to talk about transparency, often what comes in the door as a sample and what comes in the door as the job, differ. So transparency is a 2 way street.

It is better to get a good sample, multiple assays, and set your estimate on the lower end of your results. But the reason turn around time is so long in refining of boards is they have to wait for the lot to be homogeneous and sampled. That means burned or pyrolyzed, and smelted into bars that can be accurately assayed before payment.

It is a huge mistake to promise a firm payment amount based on a sample you didn't take which you do not leave yourself room for variation. There are plenty of guys who were once in the refining business that tried that business model.
 
Guys, you are forgetting. I am in Asia...

I normally have about 5 hours to offer the price. That's right. Material comes in at 10am, by 4pm already gone, Chinese buyers offer a price and take it.

This time was an exception, they gave us 2 weeks because they want to start doing business with us. But they warned us, best case scenario we will have 1 day.

This material sold for 7 USD per kilo. I do not know how, I do not know why. Chinese came and offered this price.


I honestly have no idea how they do it. I know for sure that we can offer better price than Chinese, but at the same time since I dont know the content, I dont know how much to offer. Somehow Chinese seem to know...
 
hestati86 said:
Guys, you are forgetting. I am in Asia...
It would be easier to remember if you added your location in your profile, now we only see USA as country of origin.

Göran
 
g_axelsson said:
hestati86 said:
Guys, you are forgetting. I am in Asia...
It would be easier to remember if you added your location in your profile, now we only see USA as country of origin.

Göran

Good point. But my point was that nowadays Chinese anywhere in the world will not allow you to sample, choose, select and bla bla bla. Mee to I'd love to run lab analysis on it, but suppliers just ignore buyers like that. Buyers from China come with bag of cash and pay. And they must be profitable too, because they keep on coming back...
 
Let me get this straight, normally you will get to look at the boards, do some math or look up some history (which you don't have) and within 5 hours give them a price.

Well Jon, (Anachronism) said;
I've run some of these and had very little return.

And the Chinese guy's are paying $7,000 per ton but your surface area calculation says it has 400 grams per ton. So your calculation says there is $15,000 worth of gold and you built in a 20% safety factor.

So the Chinese buyers are doing what most do and giving themselves plenty of room. The seller is the loser here and he needs to be educated.

But if you are a middle man and not putting this material into a sample-able form before shipping, you will be subject to the same screwing the Chinese are giving the seller.

Profitable refiners sample and assay before bidding. Some can develop histories which allow them to bid based on the content and their experience. But they give themselves room. Without this experience or the facilities to do the sampling and assays, you are in a position to take a leap of faith. So it's either jump in or go home.
 
hestati86 said:
Guys, you are forgetting. I am in Asia...

I normally have about 5 hours to offer the price. That's right. Material comes in at 10am, by 4pm already gone, Chinese buyers offer a price and take it.

This time was an exception, they gave us 2 weeks because they want to start doing business with us. But they warned us, best case scenario we will have 1 day.

This material sold for 7 USD per kilo. I do not know how, I do not know why. Chinese came and offered this price.


I honestly have no idea how they do it. I know for sure that we can offer a better price than Chinese, but at the same time, since I don't know the content, I don't know how much to offer. Somehow Chinese seem to know...
It was much the same as when I use to run a navigation course on Dartmoor.
Most chaps would be impatient and want to run off in the first direction that came to their mind.
Notably, fewer would sit and think for an hour or two before quietly setting off straight line for their target.
The first set would also eat all their chocolate on the first night and run out of energy by mid week.
If someone is impatient and insists on a gut valuation good for you, you have no choice but to value it at the bottom end.
You then take your time and you are going to at least be in profit maybe even make a killing if the wind is good.
But you should also offer the better route rather than use manipulative or cajoling methods to get them to accept such an offer.
 
4metals said:
Let me get this straight, normally you will get to look at the boards, do some math or look up some history (which you don't have) and within 5 hours give them a price.

Well Jon, (Anachronism) said;
I've run some of these and had very little return.

And the Chinese guy's are paying $7,000 per ton but your surface area calculation says it has 400 grams per ton. So your calculation says there is $15,000 worth of gold and you built in a 20% safety factor.

So the Chinese buyers are doing what most do and giving themselves plenty of room. The seller is the loser here and he needs to be educated.

But if you are a middle man and not putting this material into a sample-able form before shipping, you will be subject to the same screwing the Chinese are giving the seller.

Profitable refiners sample and assay before bidding. Some can develop histories which allow them to bid based on the content and their experience. But they give themselves room. Without this experience or the facilities to do the sampling and assays, you are in a position to take a leap of faith. So it's either jump in or go home.


Sorry, I don't understand. Yes, my surface calc based on 20 micro inch layer gives me 400 grams, but if this is in fact 2 micro inch? Then we are talking 40 grams, right?

Unless they have a way to measure how thick the layer is, are they just gambling? But they seem to be coming back, means they're making profit.

BTW, seller has really no idea. He bought it for say USD 2 and wants to sell for more, that's it.
 
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