Geowizard

Crushing And Milling

35 posts in this topic

     There is pro and con to everything. The con to the model you refer to takes minus one inch pieces. That's fine for sampling. The pro to the crusher that fits on top of the five gal bucket is that it is easier to carry into the field for sampling. Another con is that you have to make several passes to get the material under a hundred mesh nor smaller. If you are referring to a different model than the one that I am describing, please correct and educate me----K Rose

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K Rose - With 100% minus 100 mesh without screening steps in between, you can have issues of over crushing. Particles which are too small is a problem and may actually decrease your recovery, especially if you are using gravity based systems.

I was actually discussing this very recently with someone who makes milling equipment - over crushing is a real problem.

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"... over crushing is a real problem."

As well as crushing(one form of comminution)is usually the major expense in the recovery circuit and so over-crushing adds to the expense. With a small profit margin, saving a few bucks per ozt recovered can make a difference in your project's viability (especially if you're married).

eric

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     Chris- thanks for the info. You learn something new everyday when your willing. I can definitely see where there can be a problem when dealing with free milling gold being extracted by means of gravity. I have been led to believe that when you are leaching, you want to have your ore as fine as possible. I realize that there are a myriad of different scenarios involved depending on the type of ore verses the type of leach. So hypothetically speaking, what range of particle size should a person aim for when dealing with free milling gold , then what range if you are going to have to leach, depending on the type of ore?----K Rose

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It all depends hugely on the type of ore. Is the gold in Sulfides? Is is free? what size is the gold? Is it encased in quartz or other minerals? Many commercial hard rock mines will do 80 or 100 mesh, but screen between steps, so the ore is not over crushed. Once you reach the desired size, you don't want to keep crushing. Even with leaching - you don't want to over crush - you can produce an ore that fluids won't flow through - think of trying to flush water through a bed of solid clay. The water just sits there and ponds up . If you crush your ore so small that it packs in like clay, it can be a real pain to leach.

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Do you have experience with this product?  From the little information I can find it looks to me like a guy with a large rotohammer and a chisel bit could easily out work the mirco blaster.  Please correct me if I am wrong but I think the mirco blaster looks like a parody, 

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Geo, that is all good stuff :)  BUT  you answered my question like a politician would answer if they tied a single knot or a double knot in their shoes today. :)

 

I want to know if you have successfully used the micro blaster with good results.  It looks to me like it is not capable of doing to job in an efficient matter.  Since you have watched the videos you know what I mean. :)  From what I can tell it struggles to break rock even in multiple stages of use upon the same rock/ore.

 

So if you do have first hand experience with this product it would be great to hear more. :)

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The micro blaster is designed to break boulders in placer operations. It can blast inside mines, but I would not recommend it if your intent is production of rock for milling on a larger scale. As usual, your intent and the work you want to accomplish will make the difference as to if any particular tool will suit your needs. I've talked with the Micro blaster guys who designed and market the product on a couple of occasions. 

 

Unlike what Geo implies, blasting is not really used to crush rock for milling, its used to break rock for excavation.  If what you are wanting to do is break rock on a production basis, then more conventional methods of compressed air drilling and blasting is recommended - of course that is not cheap. If you you just want to pop a rock here and there or bring down a single widow maker rock inside a mine, then the micro blaster might be a good choice. It is a low cost easy to use tool, but very limited in what it is best suited for when it comes to production blasting.

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A neighboring mine has been using the micro blasting inside their mine to do further excavation.  They seem to get farther hand drilling and chipping.   :D

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So Chris, I am crushing  4" rocks with a GS5000HD Gold Stryker Impact Mill,  and coming out with 30- material lots of it 100- then.  Washing it thru a 12" trommel and 8ft of Gold Hog matting.  At the end of the sluice I have a 5 gallon bucket to catch any heavy material and runt that thru the spiral wheel.  Only way I have found to run gravity to recover my micro gold.

Think I may be over crushing?

Thoughts?

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I have a question similar to Rabbit's.

 

After crushing to 50-200 plus or minus, I am looking at using a Gold Cube for concentration. In addition to gold, the ore contains silver, lead, and copper. Will these "middle" values be captured?

 

I appreciate any thoughts or input!

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rabbit,  you're saying that the sluice catches the micro but not the heavies?  or, is it the other way around?  if the first is correct, add gold hog matting to catch the heavies too.

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So Geo, why would not mining companies require their employees to do the same and break all rock to minus 2 inch if it reduces work and saves money?

The big mining companies do not do this. Do you think you know something they do not?

If they specified minus 2 inch, no primary crusher would be necessary and they could go directly to a ball mill.

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Blasting large blocks of ore is NOT the same as blasting small blocks.

Why? Both require the miner to drill holes, both require the miner to load the holes with explosive, both require the miner to detonate the round.

Are you saying an 8 x8 foot passageway done under contract for a small miner is that much different that an 8x8 foot passageway done for a large miner by an employee?

Why don't big mining companies both above and underground require their employees to blast to minus 2 inch? It would save a lot of money not needing to put their rock through a primary crusher before it goes into a ball mill, so why isn't that done?

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My Gold Cube catches 99% of the chain filings from my impact mill so I'm guessing the "middlings" would get caught just as well since they are similar or greater density than steel. In the instances I've had pyrites in the ore it definitely catches it but I haven't measured efficiency on them since I don't process the sulfides but I don't see many in the tailings.

 

I tried a lot of different sluice setups with varying degrees of success until someone recommended the Gold Cube and it has worked the best, was worried about speed but it processes a 4" impact mill output pretty steadily, any faster and it bogs the chains down.

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Back to the little impact mill that sits on a bucket. A question came up the other day about just how fine it would take material down to if you were to keep running it through over and over. Does anybody know just minus what mesh it will actually take your material down to? Now keep in mind this is purely a hypothetical question. This is a matter of curiosity only. The manufacturer mentions achieving a minus 200 mesh in about 8 passes when starting out with 1/2" material.The implication seems to be that if you keep re-running the material, it will keep reducing to a smaller mesh.----K Rose

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