Geology & GeoMetallurgy

Geology & GeoMetallurgy 2017-04-04T06:58:01+00:00
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How to sample an ore or waste dump (10 replies)

Bill Rico
1 year ago
Bill Rico 1 year ago

Have anyone had any success with getting a reasonable sample from an ore/waste dump (the sample will define which it is)? I am assuming that RC is the way to go but are there any extra precautions (e.g. casing) which will help in getting a sample suitable for evaluation?

David Kano
1 year ago
David Kano 1 year ago

The usual answer I get on this one is to try sonic drilling as it is least likely to blow away the fines. The usual problem with this is will it get through the large rocks? My questions would be what are you trying to estimate (local or global) and if local are you trying to locate 'higher grade' parts of the dump?

The conclusion as the Sampling Conference earlier this year on a related question is that you can't get reliable sample from waste dumps - albeit we geologists are still asked and continue to try. Perhaps drill a bit a patch and the batch feed that part to see if you are getting any confidence at all as to what the drilling indicates. 

Dizzy Flores
1 year ago
Dizzy Flores 1 year ago

There is a reliable way to sample a waste dump: dig it, process it wholly and calculate the mass balance!
More seriously, RC or sonic drilling is useful tools as most waste dumps are stratified, according to previous extraction and processing history. But they will not provide the same results. It all depends if you plan to take the best fraction of the dump, or if you plan to mine it in bulk.

It depends also of the constraints on residues management. If local regulations (or corporate governance) require a clean, well managed final repository, bulk mining and reprocessing of the dump is the only option. This will require a precise calculation of composition and assessment of waste behaviour vs. AMD. Sonic drilling or trenching!

1 year ago
Gruppen 1 year ago

I have had some experience with sonic drilling and agree with you that it appears to give the best result. Also agree that trying to get a local estimate is probably a waste of time, so estimating on a global scale it your best chance of getting a closer result.

John Koenig
1 year ago
John Koenig 1 year ago

Sonic Drilling designed by BoartLonyear can be successful. It uses thin wall rod technology and advances casing every 3m with every run (1.5m or 3m).

Ace Levy
1 year ago
Ace Levy 1 year ago

As one responsible for payment of a sampling program, I agree that sonic drilling is probably the best option. The number of samples taken and their proximity to each other will help provide a more accurate estimate of the grades. Whether samples are taken vertically or horizontally in a given pattern is also a consideration. This all begs the question of economic value vs. cost of sampling. It is good to have some background on previous production grades and a good number of hand samples to determine whether the drilling is worth it. Just my two cents from an economic perspective!

1 year ago

I have to agree with you. Due to the nature of the construction of an ore/waste dump there is no simple way to assess the values present. Variable truck size used in dumping material is one problem, size range of particles dumped; variations in material dumped and dump stability come to mind as some of the potential variables faced. He is right about the Sonic drilling as long as the particles are small.

Dizzy Flores
1 year ago
Dizzy Flores 1 year ago

It points to the necessary compromise between sampling and analysis costs, and vertical resolution. Field instruments, and especially portable XRF, do not provide defendable analysis results, but most often very good geochemical profiles. This is true, not only for ore elements but also for matrixes and for valuable accessory elements. They provide the most cost-effective option to sample selection for the lab.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

As already noted, the homogeneity and/or continuity of the material contained within the dump are a key factor. Hence, does the sample have to be perfect? The issue really is what is the practical / realistic extent that can be assigned to grades obtained from even the very best sample? Challenges and costs associated with obtaining samples may need to be balanced against spacing of samples both horizontally and vertically given the dump geometry and method of retrieval. Close spaced drilling and small sample intervals are best in my experience. But even then there will be surprises. So, when estimating the grade, tonnage and metal perhaps look to provide ranges rather than a specific value.

Bob Mathias
1 year ago
Bob Mathias 1 year ago

I've just reviewed a case where sonic drilling was employed to drill series of waste dumps. While I've not had direct experience with the method, the recoveries indicated by the core photography suggest that as a method for physically obtaining a sample from a broken pile it is quite good.

Reading the propaganda regarding its applications, there is suggestion that it will both cut through larger size particles while at the same time vibrate its way through a matrix of smaller size particles, so it is good for dumps where broken particulate size is variable. I would think personally though that the effectiveness of this will be dictated by the hardness of the material and size mix.

As for obtaining a "representative" sample, that is a whole different kettle of geo-statistical and sample theory fish. I would tend to agree with above comment, in that if the purpose of the sampling is for a binary yes / no or ore / waste determination, then lots of distributed little samples would give you a "feel" for the overall tenor of the dump, but I do not really see a way of suitably quantifying a global estimate for a dump geo-statistically, given that you must assume essentially random development and therefore no spatial structure.

1 year ago
OberstGruppen 1 year ago

Perhaps a bit too late but herewith a link to a site showing you pictures of sonic applied for waste dump material sampling. The stock pile is 9 meters high and consists of brick, concrete; prefab reinforced steel slabs, steel, etc. The cores here are 4" OD and the hole was cased off with 6,5/8" casing. Coring was applied dry. 1 hole took approx 40 minutes.

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