Lesson 5 - Sample Prep and Processing - Technical Level: Intermediate

howdy folks I'm Keith Lowen and this is Hard Rock University tonight's lesson is sample preparation and processing now because we have the guilty and the generator and the crusher we take big samples why because big samples are more representative than smaller samples on the other hand if you don't have all this equipment you're pretty much going to be confined to a few pounds of rock and you just simply take that you do a good job of getting the sample and then take it to the laboratory and they do all the sample prep on the other hand we can do all this and we're not only getting a good sample but then the vast majority of the rock that we prep we then run over our extraction apparatus and we determine what recoveries we get what grinds we need whether we're recovering most of the gold is at three milling is it bound up in the sulfides all these sort of things we need to find out the in terms of not just how much gold is in the rock but whether or not you can actually make a profit getting it out of the rock so to do that you actually need to do small scale processing first thing we need to do is take the rocks and make them small enough to fit in the crusher this is a keen RC 46 crusher I love this little thing it'll take rocks about as big as your fist and crush them up this is substantially bigger than my fist so we need to make these things a little smaller when we take them we leave them big because a it's quicker that way and B you don't break it and lose fines now this is a half inch steel plate actually found it laying on the road one day definitely need safety glasses for this now this is hardcourts as you can tell it does not break easily okay we'll go ahead and set that one side for the moment Wow that works better then we take these pieces and throw them in another bucket and keep working it down I have the cinder blocks there to keep most of the rocks on the plate okay so we've broken some rock and a reasonable-sized pieces got the crusher started now keep the safety glasses on so you could see how fast get chews up the rough or roughly 500 to a thousand pounds an hour depending on the hardness this is really hard courts so it tends to take a little while then I reground at once and this is now about 70 percent passing 30 mesh or 0.030 inch opening size now we have to split it down to get a normal size sample now I've already crushed the sample from the top of the shaft and rolled hollow the vein there and for in the middle of the shaft and I want a 200-pound sample and I didn't quite have enough in either one so I'm actually going to composite them I've already taken individual samples from each one to send off to the lab now I'm going to composite them and get a sample of the composite also this is called a sample splitter and it has chutes going opposite directions now this is a very simple one that I made myself the nice ones run yeah three to five hundred dollars or more but this will do the job I've had it for years and I'll just use it like this it's one of the buckets and editing by the color that looks like the middle we just by the way you see the dust right now I'm kind of staying out of it have you had any significant heavy metals in here mercury arsenic things like that you definitely one thing to wear good dust mask I'm not wearing one because I've got a microphone you need to be able to hear me so I'm just basically staying out of it this is pretty clean or it has very little lead in it it has mainly iron but the silica is not good for your lungs no matter what it is dust is never good for you I don't know if you can see you know I think I'm going to have to turn those buckets around so they can actually see what's happening we're possibly not here we go what's happening there you once you have split the sample into two equal halves remove one of the halves replace it with an empty container and split it again this will give you two portions one 1/4 and one 3/4 continue this process again and again until you get the size sample that you need in our case we're going to be sending it to an assay lab so we want about 2 pounds of material once we get down to that level we bag it label it and ship it for assay so we've now crushed about 200 pounds of vein material we've split off a sample for laboratory analysis and now it's time for us to actually process that 200 pound sample on our experimental table here this is our prototype RW 28 rogue wave heavy mineral separation table and it's going to produce a number of different products there's gonna be super concentrates from the gold trapped concentrates coarse tailings fine tailings coarse slimes fine slimes slimes are the very fine materials that don't like to settle easily and I want to capture all of those separately and weigh them and assay them to find out where the heck the gold is going and how much is where with any luck basically the gold will be both in the super concentrates and the concentrates nothing else will have much so everything else has its own collection container except for the fine slimes which just use the recirculation tub so I'm going to put a catch tray in the recirculation tub and it will catch a clean sample of the slimes however we will not know the weight we'll have to infer that by weighing everything else subtracting it from 200 pounds and that's our fine slime let me put this in here so that's the first one of the sample and this is how much oversize we have left now we have to go and regrind this and run it and now we rerun the course material that's been reground very important to run 100% of the material where you can't tell for sure what the results mean now you folks may have come up with an interesting plot what ends of the gold is bigger than that input screen because gold being malleable will not crush if you have a Beebe 0.035 inches in diameter which wouldn't go through that screen they go through the rolls crushers that sucker is going to be 0.05 0.06 so something like that so if you got coarse gold is never going to get onto the table because you have to screen it so what do we do is very simple we keep regrinding the course until it's a small enough quantity to hand pan and then we'll hand pan and that way if there's any coarse gold we'll find it in the pan so these are our course that we rejected off the input screen I'm gonna pan this down to see if there's any coarse gold in our sample here okay get the iron out of there now you can do a standard tail it out technique I don't see anything with the naked eye I'm gonna get my loop out nope nothing that's what we got from the gold traps okay so we've processed the 200-pound composit sample on the table we've taken the various fractions that came off of that table and dried and weighed them and what we came up with is this over here 87 pounds of course tailings here 32 and a half pounds of fine tailings here 22 and a half pounds of course slimes 14 and 3/4 pounds of concentrates and an estimated 43 pounds of fine slimes can't weigh them because they're just too fine to collect very well so that's what we have now and now there's two things we need to check first of all we want to check the recovery of the table and secondly of all we want to check what's known as the mineral liberation when you have one mineral bound to another and you crush it there comes a point where virtually all the particles are either one mineral or the other not combinations about what that size is depends upon the or the minerals etc what we're specifically trying to do is get the gold broken free from the quartz if it's still in the heavy minerals that's okay because then we can play games with those a heck of a lot cheaper right now we took 200 pounds and turned it to fourteen point seven five pounds so it'd be a lot cheaper to play expensive games with this than the original Lord now first thing we have to do is see did we get a good separation of the heavy minerals or is there a lot of heavy minerals still left in there okay what I have here are the light materials panned out of the coarse tailings here is the heavy materials and here is a reference sample of the head or now I'm not happy with that it looks to me like we only got about 75% recovery and we often get much better than that so I'm going to rerun this or over the table again if you're not going to listen to your results you shouldn't even bother running the test the tests say the table didn't work very well we had a lot of silt in it it was impossible for me to see what was going on I may not have had adjusted right the silt itself might have affected the viscosity of the water I don't know but I'm going to redo it I've also tested these others the fine tailings and the coarse slimes still have way too much heavies for my taste again about 75% recovery the fine slimes on the other hand are virtually barren of any heavies and at this point we've recovered half a gram of gold for about one-sixth of an ounce per tonne of gold in the head or actually recovered that's below our target figure for operational mining but we also have to assay what's in the heavies the heavies themselves may be very very rich and more than make up for it we might double or triple the amount of gold in the ore when we take into account the heavies that'll have to wait for an assay we are going to try and regrind those a little bit and see whether or not we can get more gold out of it that way also well here we are and we've processed the coarser materials from the last run again they had to be dried for weighing so the easiest way to break them up is to run them through the crusher again just for thoroughness I decided to run them through twice because I could ran them over the table again and here's what we have left 48 pounds of course tailings 15 pounds of fine tailings 12 pounds of course slimes 4 pounds of concentrates and the rest is in the fine slimes hand panning all this which I have done indicates to me that we're probably well in excess of 90% recovery on the heavy minerals however we do not know what our recovery is on the gold because it can be bound up and things so now it's time to send off samples to the assay lab we're going to do that now and when we get the results back I will be able to finish the tape give you the results and explain what information we've acquired from all this work

Channel: Hard Rock University

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Keywords: prepare an ore sample, sampling mineral ore, ore samples, representative sample, sampling lode gold, send a sample for assay, splitting ore samples, small mining, gold mining, mining claims, sampling ore deposits, crushing ore samples

Id: fzL5JI80AHw

Length: 19min 25sec (1165 seconds)

Published: Sun Jul 26 2015