Gold naturally

Originally Posted by alloy2

Scott I used an abrasive in the ball mill to abrade the gold free from the boards, no labour involved with clipping off fingers with a huge savings in chemicals. The nickel underlay that the gold is plated onto is tough and does not wear off.

Tin solder is soft and wears away into the abrasive material, you can screen out the MMLC's and ram chips for further processing.

Just remember to rinse off any powder sticking to the boards once removed from the tumbler.

I ran 276 pounds of gold fingered ram using this process,

There are also a few other ways, like an ice blaster. It operates as a sand blaster, but with ice. It will strip the gold and a bit of other material, it needs to be incinerated really well after but I have had excellent results doing this in a glove box where nothing is lost.

Another way is straight incineration, where all the board material and all you are left with is the metals, and then those processed with wet chemistry, I have done this as well but it's far too much work to be more viable than what I am already doing.

Currently, I load boards into a tank by clipping them onto a lengthwise chord that runs the length of the tank, a small electric motor connected to the chord draws the boards across the tank. I have another sump tank under the large tank with a polypropylene sponge (Because it does not dissolve in AR), a pump in the sump that pumps the solution back into the tank through several jets that agitate the solution. The solution continually circulates by gravity through a pre-filter, that also adds oxygen, down into the sump through the poly sponge that filters the gold foils. When the sponge becomes loaded, I simply remove it and put the entire poly sponge into AR, when dissolved the sponge is put aside and used to replace the next pregnant sponge. I have a drain with a valve that will move solution into a third tank where I recover the metal values and resolve the solution so it can be disposed of. I like this method because it's load and forget, and doesn't take a lot of labor to operate, and strips the gold fairly quickly. I keep huge salt water tanks and just simply used the same technology, filters, sump, etc and altered it where needed. The most expensive part is the acid resistant pump.

Your way also works, but as gold is soft I try to stay away from anything that might rub it off onto equipment or tools. Because boards have a much lower recovery value though, I would prefer incinerating chips, or processing cons or industrial scrap/waste. I live close to silicon valley so I get everything from sputtering targets, to scientific samples, to testing targets that have heavy gold plating.

I enjoy your posts, people who refine tend to think in specific ways when it comes to recover values from material. You seem to use mechanical methods to recover values from material which I can appreciate. Keeping it mechanical circumvents a lot of the problems that wet chemistry for example can create. My personal favorite however, and what I love doing most is fluxing/smelting. I'm to the point where I can look at the slag and know how to alter the flux and smelting to produce results I am looking for. For the last 6 months I have been smelting using induction, and using clay/graphite crucibles which are not really intended for induction technology but hold up far better to aggressive flux than graphite or more expensive crucibles. The crucibles have to be carefully seasoned or bulges will form on the inside of the crucible which will make the fail much faster, but if done correctly and carefully clay graphite works really well. I am currently getting between 35-40 uses before the crucible looks like it's going to fail.

Thanks for your posts, I do enjoy reading them!

Scott