Crushing black sands

[Dr. Meh]

What's the best way to grind black sand to powder to release the gold and platinum?

 

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[golden sluice]

Hello dr.Meh! Welcome aboard!

I find that if I have a can of black sand and want git the gold I use the a mortar and pistol method. Just grind it up into powder and pan it in soapy water with a magnet under my pan to slide that pesty magnetite away from my gold. The I snuffer bottle it up and then re pan it, cause small gold is harder to seperate, being as small as it is,

Another method is to heat it up dry and then pour it into ice water. The metal contraction from temperature change cracks free the gold... so they say!

 

[goldenIrishman]

Welcome to the neighborhood!

The second method Golden Sluice mentioned is often referred to as "Shake and Bake". While it is an easy way to release more gold, there are a few things to keep in mind while doing it. I've been doing this for some time and these are pretty much random thoughts on the subject.

First off it should only be done outdoors! Some areas have a lot of mercury (natural and/or refined) and when the sands are heated it will go into vapor. You do NOT want to be breathing that stuff!!!!

Next on our list is the fact that the greater and more sudden the temperature change the more effective this method works. I try to get the sands up to about 450 degrees before pouring them into the cold liquid. when the sand hits the cooling bath it should sound like Rice Crispies on STERIODS.

I stated it as liquid because depending on where you live (or the black sands came from) you may get better results by dousing the hot sands in a mixture of cold vinegar and salt rather than in ice water. In many desert areas the gold will have a coating on it that is often referred to as desert varnish. This is some tough stuff to get rid of at times but the vinegar/salt mix works very well for getting rid of it. The vinegar salt mix is a super saturated solution. Keep adding salt until the vinegar will not dissolve any more. Mix it outside as it will release a small amount of chlorine gas and don't use a container with a tight lid. Instead of shaking, stir the mix and stay up wind as you mix.

I always try to make sure that all of the magnetic sands have been removed from the materials before I do the shake and bake. The metallic content seems to hold heat longer and because of this it will heat up your cooling bath much faster. So you end up having to chill or replace it more often when you're doing large batches. i went through a LOT of ice until I figured this one out.

Try to keep your batches small because it's really hard to get a large batch to heat evenly so some parts might not crack like you want them to.

Last but not least... Don't forget to wear safety glasses/goggles while doing this. Those hot sands will really sputter and splash when they hit the cold bath and no amount of gold is going to be worth your eyesight.

Feel free to pm me if you have more questions on this method.

Jeff

 

[KevinInColorado]

Wow, Jeff, best description of shake and bake I've read anywhere! I would just add to do this outside even if you're sure there's no mercury in your concentrates since other noxious stuff like sulphur is also a common ingredient and that will stink up the house in a big way!

Another method of crushing is to use a coffee grinder (no, not the one at the grocery store!). Probably don't want to ever use it for coffee beans after that though right?

 

[Dr. Meh]

Thanks for all the welcomes! I have never heard of the shake and bake method and find it intriguing. Does that release the platinum as well? Have any of you ever used a blue bowl after shake and bake or grinding it to powder? If so, does the blue bowl work on platinum as well? Sorry I keep harping on the platinum but we had an assay done on our raw material and it came back very high in each (gold at $130/yard and platinum at $300/yard). The assay guy thought something was wrong with his equipment since the platinum was reading higher than the gold but subsequent tests on different equipment yielded nearly identical results. Needless to say, we're excited and want to make sure we use optimal methods to extract the most from the material.

 

[KevinInColorado]

Platinum being a metal, shake and bake will work on it. Being as it's just slightly heavier than gold, gravitic separation such as panning, blue bowl, shaker table, etc will all work on it. The hard part may be separating the gold from the platinum since their specific gravities are so close to each other. Anyone have tips on that?

 

[Lotus Geologist]

Pretty sure you need advanced laboratory skills and strong acids and/or electroplating baths to separate gold and platinum.

I recall sending off a bunch of scrap gold to a refiner while in grad school. In experimental petrology we often use gold crucibles/capsules and platinum-rhodium thermocouples while conducting high PT petrologic experiments... Anyway, all I sent to the refiner was scrap gold, or so I thought... The refiner gave me a call that he was having a bear of a time refining to pure gold due to the presence of unknown impurities. Even after I told him there may have been some platinum and/or rhodium mixed in with the gold I don't think he has the facility to separate it... This was back around 1997 so things may have changed for small refiners.

L.G.

 

[goldenIrishman]

LOL I just had a vision of Kevin walking into WalMarts' coffee section with a couple of 5 gallon buckets of black sand and grinding them up. That would be funny to see.

You can use a coffee grinder but don't expect the blade to last long. The impact of the materials against the blade will eat it away in no time. (Don't bother asking how I know this as I'm still down one coffee grinder! ) Coffee beans are a LOT softer than black sands. While the blade is in good shape it works like a champ giving you almost a talcum powder (Gold Espresso?) grind.

The PGMs should stay in the pan with the gold due to their weight. You might find this link helpful... Gold Refining Forum.com ? Index page

 

[KevinInColorado]

LOL, I will confess I've fantasied about dumping a bucket of black sand in to one of those grocery store grinders!! But, yes, I meant the little home style ones which are not durable enough for high volume it's true.

Now you have me thinking...I wonder if I could get my hands on a grocery store style coffee grinder? I bet you can even buy replacement grinding bits for those!

 

[jcazgoldchaser]

Ballmill.

 

[KevinInColorado]

Ballmill.

yes, I know. In fact a grocery store coffee grinder is just as expensive as a workshop type ore crusher (yes, I checked) so it's just funny to imagine ;-)

 

[jcazgoldchaser]

yes, I know. In fact a grocery store coffee grinder is just as expensive as a workshop type ore crusher (yes, I checked) so it's just funny to imagine ;-)

That's what the overlay wear plates look like {in my mind}. I don't think those coffee parts would last with sand and gravel.

 

[KevinInColorado]

So you're saying I should sneak into the grocery store and use theirs? LoL just kidding

 

[goldenIrishman]

Well after wearing down the blade on my spare coffee grinder I took it apart to see if it would be possible to fashion a better blade for it. I did learn that the blade just screws on to the shaft of the motor so it will be possible to make up a new one. I just have to figure out what to make it out of is all. I'm going to have to take my time and try to make sure that the blade is as balanced as I can make it so it doesn't shake the rest of the grinder apart. Carbide would be ideal, but I don't have the tooling to work it. Stainless is what the original blade was made out of and it was way to soft to last for any length of time. So the hunt for a material that's going to be long lasting and able to be worked with what tooling I have is on. I'll let everyone know what I come up with.

 

[B H Prospector]

Well after wearing down the blade on my spare coffee grinder I took it apart to see if it would be possible to fashion a better blade for it. I did learn that the blade just screws on to the shaft of the motor so it will be possible to make up a new one. I just have to figure out what to make it out of is all. I'm going to have to take my time and try to make sure that the blade is as balanced as I can make it so it doesn't shake the rest of the grinder apart. Carbide would be ideal, but I don't have the tooling to work it. Stainless is what the original blade was made out of and it was way to soft to last for any length of time. So the hunt for a material that's going to be long lasting and able to be worked with what tooling I have is on. I'll let everyone know what I come up with.

I use to work for a welding shop that did hard face overlay on crusher rollers used in crushing coal into powder to burn in power plants. It is also used to make edges stronger by running a bead on the edge. It is very strong and long lasting. May be pretty hard to lay it on a thin coffee grinder blade.

 

[goldenIrishman]

I was thinking of brazing something like carbide edges on it but since I sold all my welding gear when I moved to Georgia 8 years ago that's pretty much out until I can find someone local that could do it for me. I was thinking I could remove the blades off an old straight router bit and put them on the grinder blade. Heaven knows I've got enough router bits laying around the shop to work with.

 

[mxer47]

I think carbide might be too brittle, it doesn't like shock. It chips and flakes off. Hardened steel maybe, how about a planer blade or two crossed? Drilling would be an issue.

 

[russau]

well depending on how much BS you have to crush, what i made for crushing my BS is a homemade ball mill. i made it out of a 4 inch stainless steel tube and i cut out a S.S. disc to weld in one end of this tube. the other end i use a 4 inch sewer plug. on the end that i welded a plate over, i centered the peice and drilled a 1/4 in. hole to attach a Love Joy coupleing and the mateing coupleing is attached to a variable speed gear reduction motor.this tube is mounted on a angle to keep the BS towards the back of the tube to keep my BS from spilling out.i got a bunch of old machine bearings and busted them apart for the SS balls..... it worked great for a long time untill the magnetic dusts got to my motor and cooked it. also you can cleanout a cement mixer if you have a lot of BS to crush.and you can put any iron objects in it to keep the cost down.i lkied the SS balls because they are harder thand the BS im crushing.

 

[Dr. Meh]

Thanks for the tips everyone. Any advice on separating platinum from gold? Or just refining platinum in general?

 

[goldenIrishman]

I'm looking into that as well Dr.Meh. I've been finding a "mystery material" in the wash on my claim. I KNOW it's not lead or mercury covered gold but still have to do more tests to determine exactly what the heck it is. It's VERY heavy, metallic silvery gray in color and when you tap the pan to walk the gold up to the edge, this stuff goes right on up with the gold. It laughs at a propane torch and I don't have any map gas on hand at the moment to see if it melts with the higher heat. If it does turn out to be in the platinum group I'll have to figure out how to refine it. I do know that there was about 6,000 oz of silver recovered in that area between 1875 and 1900, but this is in a placer and silver found like that is usually black from oxidation. I'm not ruling it out but it just seems unlikely given the color of the stuff. Of course it would be my luck that I go prospecting for gold and end up finding platinum..........