How to capture gold in quartz grains?

[ConceptualizedNetherlandr]

This is where gold is lost.

It was in your system, pan, sluice, contraption, whatever, but not any more!

I have access to some sand. Actually, lots of sand. I grabbed about a gallon by screening it through #4 on site. Lots of big stuff in the discard pile on site.

I gave it a very mild and quick hydraulic separation ( blew off maybe 50%) then classified through 10 and 20 resulting in 3 groups.

This stuff is not concentrates. More like mildly worked bulk material.

So I put some in a jar (the 10- 20+) and shook it around and checked it with a hand lens I noticed some of the quartz sand has gold in it. I did a vibration separation on the flooded jar and got nice black sand grouping, and the quartz with gold in it ABOVE the black.

How are we supposed to catch this this stuff? How much of this are we all throwing out? Imagine the ratio of this gold in sand grains compared to the fines.

I took an image thru the jar, for scale there is a 0.7mm pencil lead in the second image. Very tricky to get the images. This particular grain is larger than 1mm and would be retained on a 16 mesh.

 

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[ConceptualizedNetherlandr]

90 views and no one has any help

So ... I took some of the coarse 4- 16+ and put it in a jar and gave a shake.

So hard to show the color, but these certainly are big enough to worry about.

Does anybody else look closely at the bulk material being carried away?

How can we catch this stuff? There is way more gold in it that stuff than all the flour.

Do we have to start grinding the entire placers?

 

[ConceptualizedNetherlandr]

BTW, just a couple shakes and this was near the bottom. This stuff is big enough that I used a spoon to scoop out the piece of interest and the other came along as a bonus.

 

[johnedoe]

Get yourself a good metal detector and go over your tailings every now and then............

 

[KevinInColorado]

I'm interested in this thread but have no good suggestions myself. Tough question I think!

 

[goldog]

Are you sure there is gold. I'm sorry but the Picts don't look like gold to me.

 

[ConceptualizedNetherlandr]

Get yourself a good metal detector and go over your tailings every now and then............

1) There are no tailings. This is pretty close to bulk material.

2) Even if one were to sluice this stuff, and we know these quartz inclusive gold particles are going to be in the tailings with or without generating a beep, then what?

We are back to square one with how to separate.

The thing we search is how to concentrate this. If we had a bunch of mostly this it could be rolled perhaps. But first, this has to be separated from everything else.

I'd like to hear back from the sluicers. Do some rough field classification of what you are digging, fill a jar with about 30% and take it up to 20% head space with water, shake a way then have a good look at the bottom area.

 

[johnedoe]

OK.... my perspective was out of skew from your pictures..... definitely got to get the old eyes checked.

 

[ConceptualizedNetherlandr]

Are you sure there is gold. I'm sorry but the Picts don't look like gold to me.

I realize the scope isn't the best, but what do you think could be inside those grains that leaves it sitting at the magnetic sands interface? It survived a 50% blow off.

It looks perfect in the hand lens.

 

[johnedoe]

At this point about the only way I can think of is get enough of it to have it assayed..... Unless you know someone with a spectrometer.

 

[goldog]

You should crush and pan it. I certainly hope you're right. You don't need much. I've brought home plenty of stained, mineralized Quartz and crushed it.

You should see my leverite collection. All kinds of things catch my eye. The titaniferous magnitite alone will fill a bucket. A nice 3-4 lb specimen took a round trip home and back to the creek the other day by mistake. I'm not carrying that home twice!😖

Only 1 type ever had any gold. But 1 did so it's not hopeless.

Crush a few of those puppies and pan away.

I look at it this way; unless I know it's gold I don't worry about it. If those gold Quartz pebbles were below the black sand I'd be curious. Gotta trust your machine though. It's catching most of the gold and washing out the rest.

 

[UTAvalanche]

This is where gold is lost.

It was in your system, pan, sluice, contraption, whatever, but not any more!

I have access to some sand. Actually, lots of sand. I grabbed about a gallon by screening it through #4 on site. Lots of big stuff in the discard pile on site.

I gave it a very mild and quick hydraulic separation ( blew off maybe 50%) then classified through 10 and 20 resulting in 3 groups.

This stuff is not concentrates. More like mildly worked bulk material.

So I put some in a jar (the 10- 20+) and shook it around and checked it with a hand lens I noticed some of the quartz sand has gold in it. I did a vibration separation on the flooded jar and got nice black sand grouping, and the quartz with gold in it ABOVE the black.

How are we supposed to catch this this stuff? How much of this are we all throwing out? Imagine the ratio of this gold in sand grains compared to the fines.

I took an image thru the jar, for scale there is a 0.7mm pencil lead in the second image. Very tricky to get the images. This particular grain is larger than 1mm and would be retained on a 16 mesh.

I would say there is a good chance you are right. Like you, I got interested in trying to recover micro gold some months back. So I built a sluice that catches all the black sand and gold no matter how small in a batch of material and then I separate it out on one of my miller tables. Like you I have found it in bulk material all around my house and in the tailings that 2 of my friends bring me and most sand that I check out. Much of the gold is so small that I have to use a set of 10x glasses to see it and move it into the gold bottle on the miller table. The micro gold drops out of the black sand and just stays stuck to the mat and the tiny black sand just moves on down the table. To verify that it is gold I have to use a low power microscope to check it out. I was quite surprised to find how much of it was around. I take the 4 mesh and larger and crush them to as fine a powder as I can which releases more of the gold. I then screen it down to -40 and -60 to run on the miller table with about a 2 degree angle and very low water flow.

I have a hard time taking pictures because my camera can’t take macro’s very well. So yes, it is recoverable. Whether it is worth while to or not I don’t know. For me it is not the gold but the challenge to see whether I can recover it or not. So yes, it can be recovered. And if you can recover this size gold then anything larger will be recovered as well.

This is one of the larger pieces.

 

[Reed Lukens]

 

[russau]

Reed that is a impressive device!

 

[3xflyfisher]

Gold encapsulated in quartz and other silicate minerals has been and will continue to be a nemesis of gold miners. The relationship of grade vs particle size plays an important role here. Commercially, if the grade justifies the additional expense of grinding the ore finer it is possible to recover these values. There are commercial mines that will grind their ores to -200m (or finer!) prior to leaching to allow the encapsulated gold to become liberated and therefore come into contact with the CN-. When grinding ore this fine it becomes very difficult to recover gold using gravity methods (panning, spirals, sluices etc.). The processing expense will typically make material such as you are describing uneconomical to recover the gold from. Same applies to recreational prospecting - how much time and effort are you will to put in to processing this material to recover any values? If you have enough of the material and it grades high enough it might be worth looking into smelting it. Also, there has been some research into shocking material like this be heat the gold bearing quartz particles and then shocking it by quenching it in cold water thus fracturing the quartz and liberating the gold. I am unsure as to the effectiveness of this or whether it has ever been used commercially. Also, be aware of the safety hazards by quenching hot rock in cold water - a violent physical reaction releasing a lot of steam!

johnedoe's suggestion of having a sample assayed to dermine for sure whether you have gold or not and then decide if it is worth your effort to work recover the possible values makes a lot of sense.

 

[ConceptualizedNetherlandr]

This is a fickle lil problem indeed. I have played with the maths a bit.

But first to address that tiny spec Reed boasts about ... ... enough of them and it becomes attractive. Look at what is probably the worlds second largest known gold deposit -

Carlin-type gold deposits (CTGDs) in northern
Nevada, which contain over 6,000 tons of gold (Au), constituting
the second largest concentration of Au in the world

As mentioned before here: http://www.treasurenet.com/forums/lost-dutchman-s-mine/447362-new-show-dutchman-75.html#post4426599

This nice link http://www.nevadaexploration.com/_resources/Muntean_et_al_Carlin_Genetic_Model-2011.pdf discusses the grain size of that gold.

in which Au
occurs in solid solution or as submicrometre particles in pyrite.

At least it was in pyrite which has a density close to 5.

Now back to the math which exemplifies the problems. If you had quartz sand grains containing 10% by volume gold it would have a grain SG of ONLY ~4.32 More than plain quartz but less than even magnetite (~5.5)

That happens to = a whopping 44.73 Weight % of gold in such a grain.

10% by weight of gold in a quartz grain would result in a SG of only 2.89. That would be real hard to separate.

Compound that with size and concentration variations and it becomes a real chore for all but the higher gold concentrations. That 10% by weight is a mere 0.015 vol %.

What would we estimate the visible volume % is in the grains I have? Has to be closer to the 10% by volume than the 10% by weight to be so visible.

And I'll bet that is not so rare where people are finding placers, AND DOWNSTREAM of there. After all consider the natural processes that degrade the vein and allow the gold to move in placer fashion. The gold doesn't just pop out pure and go, the entire rock breaks down in to smaller and smaller pieces as weather and mechanical action works it. Eventually some of the gold is completely free of the quartz, but before that time it is in some varying concentration of gold in quartz. The gold that is in quartz can move farther. And for the case where the source is long gone, this gold rich sand is likely to be farther along than when the rich placer starts to thin out. As an aside: Freeze thaw might play a real big role due to differing coefficients of expansion, but only in areas where that cycle happens, and probably not under water anymore even in cold areas.

It seems self evident that hardly a small fraction of the gold shoveled or sucked into sluices is recovered.

Who wouldn't want to deal with tons of sand that is somewhere between 10 wt and 10 vol % gold? Yet everyone lets it go.

When we figure this out every one will be digging their old runs.

 

[GoldpannerDave]

Are you sure there is gold. I'm sorry but the Picts don't look like gold to me.

Try a Falcon MD20 detector to see what it really is--metal or gold.

 

[ConceptualizedNetherlandr]

Try a Falcon MD20 detector to see what it really is--metal or gold.

1) screening each grains seems like a chore, and

B) some detector could do that?