Throwing the baby out with the bath water -- CONCENTRATES

[ConceptualizedNetherlandr]

Minerals containing gold and their density/SG.

Nagyágite Pb5Au(Te,Sb)4S5-8[1] or

AuPb(Sb,Bi)Te2-3S6[2] or (Te, Au)Pb(Pb, Sb)S2[3]
7.35–7.49 (quasi telluride)

Aurostibite AuSb2 9.98

Auricupride Cu3Au 11.5

Uytenbogaardtite Ag3AuS2 7.134

Rhodite Au, Rh 15.5 - 16.8


The tellurides:

Petzite Ag3AuTe2 8.7 - 9.14

Krennerite AuTe2 8.53

Kostovite AuCuTe4 7.94

Calaverite AuTe2 9.1-9.3

Sylvanite (Ag,Au)Te2 8.2


Consider how much the cons weigh overall compared to the 'pure' gold you separate out.

Might be a good idea to do a test melt (and/or other techniques) on a representative sample of the cons from each area. No?

 

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[DizzyDigger]

For me, in the end it all comes down to two questions:

How much is it worth?

Is it worth the cost to extract?

If I had 15-20 tons of black sand then it might be worth
having it assayed, but in the final analysis there are many
factors to be considered. Transportation to the smelter, and
the additional processing costs to remove the valuable metals.

 

[KevinInColorado]

Minerals containing gold and their density/SG.

Nagyágite Pb5Au(Te,Sb)4S5-8[1] or

AuPb(Sb,Bi)Te2-3S6[2] or (Te, Au)Pb(Pb, Sb)S2[3]
7.35–7.49 (quasi telluride)

Aurostibite AuSb2 9.98

Auricupride Cu3Au 11.5

Uytenbogaardtite Ag3AuS2 7.134

Rhodite Au, Rh 15.5 - 16.8


The tellurides:

Petzite Ag3AuTe2 8.7 - 9.14

Krennerite AuTe2 8.53

Kostovite AuCuTe4 7.94

Calaverite AuTe2 9.1-9.3

Sylvanite (Ag,Au)Te2 8.2


Consider how much the cons weigh overall compared to the 'pure' gold you separate out.

Might be a good idea to do a test melt (and/or other techniques) on a representative sample of the cons from each area. No?

Yes, it's often worth a test assay. A representative sample of my non-magnetic already-processed cons showed 2.6 oz/ton. Wow! Definitely worth further processing after all the visible gold is removed

 

[ConceptualizedNetherlandr]

Safe to assume that placer miners have tossed more in tailings than recovered? It is said that gold rush areas were all worked at least twice already, and still they may contain greater mineral wealth.

 

[ConceptualizedNetherlandr]

Yes, it's often worth a test assay. A representative sample of my non-magnetic already-processed cons showed 2.6 oz/ton. Wow! Definitely worth further processing after all the visible gold is removed

Just out of curiosity, about how much visible gold/ton do you recover before that assay?

 

[KevinInColorado]

Just out of curiosity, about how much visible gold/ton do you recover before that assay?

Well, remember this is my concentrates not paydirt we are talking about. I probably pulled about 7 grams of gold out of 50 pounds of concentrates...that's almost 10 oz per ton right? The startling fact is that the visible gold is only 80% of the total gold!

 

[ConceptualizedNetherlandr]

Right Kev. I math that to 9 and 77%, but yes, surprising that so much is left behind. I suppose it varies greatly from place to place. I have no idea if all those 50 pounds came from the same place or a mix, but it might be a good idea to keep them separate before deciding which ones to go after, if any. Ever try to melt some cons? Under the right conditions you might precipitate out some gold on cooling? But then again - melting a lot of stuff for not much gold. It would be interesting to know what the specific gravity of your cons mins is. At those low SG's of some of those gold mins they might not even be in the cons anymore. We need a microscope mineralogist to tell us what we have and where to stop flushing it out

If we knew the ID of those gold mins in any particular location we might be able to target the lighter ones that are valuable.

 

[KevinInColorado]

I sent all those cons to DizzyDigger so he could process further and donate to St Jude's Children's Hospital

Sadly melting isn't enough. You need to add litharge to a well ground specimen of cons and then melt it to get the gold to collect. I did it with a 30 gram sample, that's how I learned how rich it really still is.

 

[ConceptualizedNetherlandr]

Diz didn't sound all that interested up in post #2 , maybe he is taking it off you just to ease your conscience.

Given how comparably light these gold bearing minerals are, and the implications of particle size on hydraulic/fluid dynamic separation the real life recoveries might be much lower that apparent. * The only way to fix this would be a whole lot of classification followed by multistage (multi velocity) separations. Probably not economic right now, but save those tailings for future generations

*Probably most here understand this, but in case someone might gain a better understanding:

If you had materials of uniform composition (perhaps all gold or all lead or all silica sand) but varying sizes and put them is a hydraulic seperation regieme ( like a sluice or even a blue bowl) as you increased the flow the smallest particles would come out first, then more flow - larger particles, and increase up until you are flushing out nuggets or bigger.

This is all about surface area to mass ratio. Not necessarily linear relationship. Smaller particals have larger ratios and shear/viscosity/traction forces act on them proprotionally to that ratio.

Now, if we had similarly sized particals of varying composition (like gold lead silica) the ratios is affected by mass given constant size and the seperation would be by composition rather that size. Put them in your blue bowl or sluice and as you increase the velocity first out comes the sand, increase enough more and out comes the lead, and finally speed it up to move the gold ( or as we do, shut it down and collect the gold)

Now all of that ^ is straight forward and neglects shape factors (well rounded v. angular material, flat, etc) , but the world does not present us either of those simplistic scenarios. We have a complex mixture of sizes, shapes and mineral compositons (not just minerals, some pure elements, rocks composed of various minerals etc. - not to mention colloidal suspension of fines and such.)

Page break to not lose my work.

 

[chlsbrns]

For me, in the end it all comes down to two questions:

How much is it worth?

Is it worth the cost to extract?

If I had 15-20 tons of black sand then it might be worth
having it assayed, but in the final analysis there are many
factors to be considered. Transportation to the smelter, and
the additional processing costs to remove the valuable metals.

Wasn't it you who wanted others to send you their black sands? Now you say they aren't worth processing?

I have gotten as high as 25 oz from a 55 gal drum of black sands. 55 gal is close to one ton. If I thought people would part with their black sands I would travel the Country buying and processing the sands.

 

[ConceptualizedNetherlandr]

Now where am I going with this? I am going to explore the idea that gold minerals are being flused right out of the sluice. Some stay in the cons, but in areas with these minerals present the flush might be astonishing. The other thing that might fall out is the amount of fines that blow by the systems. Of course these things have to be present at a given site before this matters.

Lets consider perfect spheres of gold and a lighter gold mineral. From the list in the OP I pick Aurostibite AuSb2 9.98. Almost half gold on a molecular weight basis. (44.8%). And my gold sphere has to pass a 20 mesh screen so max diameter = 0.841mm. Hardly matters what size we start with, but that is in the ballpark for what everyone is sluicing for, right?

Vol of that sphere is 0.31129 mm^3. If pure gold it should weigh 0.006014 grams. Surface area * would be 2.22 mm^2. SA/mass ratio = 369. (mm^2/grams) We can think of that as susceptibility to hydraulic sorting.

Working backwards that equates to a 1.626 mm dia Aurostibite sphere weighing in at 0.0225 grams, of which 0.01 grams is gold. More gold than in that 20 mesh gold sphere. Almost double.

Consider a set up - no classification - that just catches that 20 mesh sphere and things of similar SA/M Ratio. Particles with higher SA/MR get flushed, everything else gets trapped. Anything smaller and/or of greater SA/MR, bye bye. No surprise, everybody knows this. Everybody operates to some size limitation be it hydraulic or screened. Whatever the smallest size fraction recovered for a given operation the rest is blown by. A secondary/tandem sluice with slower hydraulics (larger unit) would tell you how much. Bigger zook fed 'only' by the outfall of a smaller unit. The speed could be cranked aggressively so the small one is skewed to higher concentration of gold and the second one saves any gold rich blow by. Bring home more cons and more gold to work on later via well controlled classification and separation at your liesure. For any given size you could target the gold bearing mineral densities after free gold removal, and resultant 'special' cons could be subjected to chemistry. You could just run a big ole slow sluice to increase your cons mass by being less discriminatory, but with a dual setup you would know right away and easily what the free gold situation is and have it concentrated compared to a much larger volume of secondary cons in the big slow sluice. I don't suggest targeting mineral bound gold in a small operation, but think it might be worth capturing while you are after free gold.

And ... without the secondary trap all those lighter gold minerals of lower density but larger and holding more gold also flush out depending on size up to the equivalent SA/MR. Testing cons wouldn't tell us anything about the mixed mineral blow by from the sluice.

The solution would be optical mineralogy on the bulk material (almost pre sluicing) to see what should be targeted in addition to free gold, and then appropriate classification and sluice conditions to catch it all. Any geology department would be happy to have a gander at your stuff. I'd say start with a hardly separated sample to remove the stuff lighter than the gold bearing mixed minerals. Then decide if you want to bother.

If the numbers above reflect reality, it is easily possible that in gold bearing mineral areas more gold goes off the end of the sluice than brought home free plus in the cons combined.


*It is a lot more complicated than just surface area, we have cross section to flow, sectional density and a host of other factors but lets keep this simple for now. Today we assume a linear relationship for this analysis. We had to chose some basis to explore

 

[chlsbrns]

All of the minerals that you listed in your op are denser than magnetite. We all capture lots of magnetite or maybe we are getting the minerals listed in your op?

 

[ConceptualizedNetherlandr]

You have to consider size as well. You are not getting flour magnetite, right? There is a point where the OP minerals will wash away while you still retain smaller gold and slightly larger magnetite. Tell me the smallest mesh magnetite you know you retain and I'll math it if you like, using this simple model just made up as an approximate example.

 

[ConceptualizedNetherlandr]

Another thing about everybody's cons, I imagine folks in general discarding larger chunks of 'not gold' without having any idea of mineral ID. Quarter inch chunks of gold bearing mineral tossed? Maybe even at the pre-sluicing classification stage. If you knew that 2 pound cobble was Aurostibite would you still toss it aside or take it home?

 

[GoldpannerDave]

You have to consider size as well. You are not getting flour magnetite, right? There is a point where the OP minerals will wash away while you still retain smaller gold and slightly larger magnetite. Tell me the smallest mesh magnetite you know you retain and I'll math it if you like, using this simple model just made up as an approximate example.

Actually, I am getting some very small mesh magnetite.

 

[GoldpannerDave]

Another thing about everybody's cons, I imagine folks in general discarding larger chunks of 'not gold' without having any idea of mineral ID. Quarter inch chunks of gold bearing mineral tossed? Maybe even at the pre-sluicing classification stage. If you knew that 2 pound cobble was Aurostibite would you still toss it aside or take it home?

I have a Falcon MD 20 that I could check stuff like you are talking about, but with the Bazooka in the stream or river, it simply is not worth the time to check. If it is dense enough and small enough to get into the fluid trap, I likely have saved it. If it is pretty large, it went off the end back into the creek. I see where you are heading but right now I am not convinced I should be too worried about stuff that goes off the end of my Bazooka--not here in Colorado where most stuff is pretty small.

Now, if I am looking at tailing piles or something like that, then, yes, it may make some sense. But not in the creeks and rivers here....

Good discussion and I appreciate you bringing it up, but there is still a time-reward ratio to be considered.

 

[chlsbrns]

The magnetite as well as other minerals are what most would call flour size to invisible to the naked eye. Basically the same sizes as gold.

All sluices dump some gold over the edge.

 

[ConceptualizedNetherlandr]

Actually, I am getting some very small mesh magnetite.

The smaller the mag the smaller all the other things you are retaining, good thing! Do you know what mesh? For example if you screen the fines, at what point does the Mag no longer show up?

 

[ConceptualizedNetherlandr]

The magnetite as well as other minerals are what most would call flour size to invisible to the naked eye. Basically the same sizes as gold.

All sluices dump some gold over the edge.

Hey that is not a number I can calculate about :P


But sure, if you are getting real fine then you are not loosing much small mineral gold. but what your system passes is still more gold mass than the smallest gold you get. The front end is more about mineral ID. Imagine tossing ounces and pounds aside

 

[chlsbrns]

We don't use a sluice. It's a love hate thing. We hate them because they lose gold and we love them because they lose gold. We use a vortex in a cone bottom tank to get our cons and then we use a cone bottom tank with water, mercury, hydrogen peroxide, pine oil and our secret ingredient to boil the cons. It's a twist on froth floatation. What won't float out of the tank gets caught by the mercury.