Soil or Ground Sampling

[Nitric]

Ok, another Question!

Sampling or deposit evaluating?

I don't know the terms and I'm trying to search for information on every detail of how this is done. I have a basic understanding. I want to know more. I'm looking for more on a large scale. I understand they core drill to get samples and averages, that's all I know. I also have a basic understanding of creek sampling with a pan.

But, I know a major company doesn't walk around with a pan and find some gold, then bring in millions of dollars of equipment!

I want to know more, and don't know the terms or what it is that I'm looking for in wording for a search. There has to be a process and formulas for doing this. What's it called? What field would this be considered? A type of surveying I guess? I'm guessing it's done on a grid at different depths to follow out the deposit? I'm sure soil is done different than rock.

This would be done for everything not just gold.

 

[Nitric]

I think I found it! Mineral surveying

I was trying to do a search and it was driving me insane, that I couldn't find what I was looking for, when I posted!

 

[Nitric]

Just in case anyone else is looking into the subject, here are a few I've found so far that get you going into the direction.

Mineral Survey
Mining surveyor
exploratory survey
deposit survey
Geomechanics
Geochemical

 

[goldenIrishman]

Sampling can range from a very simple test pan to hundreds of thousands of dollars. It all depends of the size of the operation in question Nitric. In my mind, the most important part of any sampling / testing process is detailed records of the individual results for each and every site a sample is taken from. Accurate GPS readings are a must so you can plot everything out on a map of the site to ID pay streaks. Of course the more samples you do and plot, the more accurate you're going to be. Unfortunately the more samples you do also means the higher the cost! Most placer sampling usually goes down to bedrock and they charge by the foot. If you're sitting on land that's 50 ft down to bedrock it's going to cost you 5X more than if it's only 10 ft. down to the bedrock. Lots of variables are involved on how much it can cost.

Sample drilling for a lode mine is a whole different game to say the least. Usually much deeper core drilling and testing of the samples is also handled differently.

Sampling can be both a blessing and a curse. More than one operation has gone bust due to testing that either was done to excess (no materials moved in the end) or not done correctly. (either in the working of the samples or bad record keeping ) When sampling is done right it can really up your game, when it's done wrong, it can put you out of the game.

And most of the time... A guy with a pan is where it all started in the first place.

 

[Nitric]

I started thinking about it...(my first mistake!lol)

They have to know what's in the ground and I would think that could be pretty accurate. So, I went looking to find information that went in depth. I still haven't found much that describes what is done. I can guess by what I've read on a few different subjects real fast, just barely touching the surface of them. My biggest problem is not knowing the terms to what I'm trying to look up. Another, is if you were to show me a map of a deposit, I wouldn't know how to read it.

as an example....If you were to drill down, start hitting it at 10 ft and run out of it at 20ft. A 100ft away you hit at 15 ft and run out at 20ft. etc.....
And this is done in a grid. Tighten up the test holes in the concentrated section. The average still has to be described. one corner could be more concentrated and thinner than the other corner of the grid that was thicker and less concentrated in the deposit. If that makes any sense at all! lol I know this is part of how they figure out how much is in a yard. Where I'm mixed up at, is the details of the average. And how it would be described.

So, the person or company, should be able to figure out almost exactly what is there and know what they need to get it out, before equipment is even brought in to mine. cost,what equipment,and how much is going to be recovered for profit.

I probably won't ever have this problem! I was just curious about all of it.lol

 

[DDancer]

I know how your feeling Nitric. I had just a basic understanding of alluvial sampling till I got down to Australia and saw what the drillers did then dug into it a bit more. While the methods are basically the same~ test holes and gridding coupled with records and assay~ I found it to be like apples and oranges the way one goes after surface deposits and the hard rock. Hehh what really keyed me off to read up on it were the holes themselves. The drillers often left different colored piles of samples in neat little lines or boxes near the hole. I then read, actually tried to read, a few drill reports. That was a headache and it got worse trying to tie them to geology reports. Have fun with the reading... me I'll stick with potholes, pans and mapping An occasional rock chip and dolly pot as well. *grin*

 

[goldenIrishman]

Yup! You're on the right track Nitric. The miner(s) can get a pretty good picture of what's under the surface with ACCURATE sampling. Of course the more samples you take and record the better that picture is going to be. When people sample a claim in the way you're talking about it is usually for a medium to large scale operation and usually done so they can make their investment back quickly. It helps to keep them digging where the highest concentrations of gold are at.

When they plot/map out the results, it's not done on your typical USGS topo map. Those are not large enough to get the needed detail. A large scale map of the claim (or part thereof if it's a large claim) is drawn out in detail. Each test location is then recorded on the map. Samples are taken and checked for gold content per yard and then that information is also recorded on the map. Exactly how and what data is recorded varies between operations and exactly what they're digging for. Doing samples like this is not restricted to only gold operations. One of the tricks when doing this kind of sampling is to lay your sample sites out in a logical progression. That makes it easier to be able to see trends as they relate to the actual terrain. If you go drilling here, there and everywhere with no plan, your picture will be like looking in a shattered mirror. The image is there but it's fragmented. Make sense?

Don't stop thinking Nitric! It's how we grow as miners as well as people. And don't be afraid to do that thinking from outside the box either! I was taught years ago. "You can teach anyone anything as long as you can put it in terms that THEY can understand." The only dumb question is the one that is never asked. I've had some great teachers over the years and I feel that the best way to pay them back for their help is to pass on knowledge whenever and where ever I can.

BTW... Check your PMs.

 

[Nitric]

I know how your feeling Nitric. I had just a basic understanding of alluvial sampling till I got down to Australia and saw what the drillers did then dug into it a bit more. While the methods are basically the same~ test holes and gridding coupled with records and assay~ I found it to be like apples and oranges the way one goes after surface deposits and the hard rock. Hehh what really keyed me off to read up on it were the holes themselves. The drillers often left different colored piles of samples in neat little lines or boxes near the hole. I then read, actually tried to read, a few drill reports. That was a headache and it got worse trying to tie them to geology reports. Have fun with the reading... me I'll stick with potholes, pans and mapping An occasional rock chip and dolly pot as well. *grin*

Maybe, I'm looking at it more complicated than what it is. Then I'm reading about mineral Bleed(? Forgot the word already lol) Anyhow, where the soil and plants have the traces of the mineral in them from a deposit in the area. I start on one thing and end up somewhere else in reading! lol

 

[DDancer]

Well said golden

You'll get into yet another ball field if you start with the biology of gold deposits Nitric That was another lesson learned down under~ plant associations with mineral deposits. Problem is gold nuggets aren't found under cabbage leaves like little kids

 

[Clay Diggins]

Here's a term for you to study Nitric. Pay very close attention to the "nugget effect" when it comes to placer sampling. "Good" numbers rarely are.

Heavy Pans

 

[russau]

Nitric here in Missouri they have a book/dvd out called "Missouri soil survey" I don't know if any other state having this(Im sure they do!) but it is done by the Missouri Department of Natural Resources and its listed in the Missouri list of publications. im sure your location has such a list . Ive noticed that some realestate companys use this in their adds for land forsale.

 

[Nitric]

Here's a term for you to study Nitric. Pay very close attention to the "nugget effect" when it comes to placer sampling. "Good" numbers rarely are.

Heavy Pans

I just looked up part of the meaning. That's the kind of stuff I was trying to find. How the averages were figured with these kind of problems. If someone says "this ground holds 1/2 gram per yard". How did they get the average with, varying depths, and concentrations etc. So, you would have to know the way it was tested and calculated to understand if they are giving you real numbers or if they did a quicky, and are giving you a average, but maybe not the average you are looking for the way you would have calculated it.


Yep, that's what I was trying to find, The variables, the error's, how to read what was done and how it was done. How it was figured and mapped. The errors that occur depending on how it's tested or sampled. Or the errors in the methods used to sample, the percentage of error.

Geostatistics! Now, this is getting deep! This is interesting!

 

[Reed Lukens]

When they survey the deposit, it's just that, it could be ½ a gram per yard 20 feet deep. That doesn't include the 17 feet of barren soil above it. Drilling a large deposit is the best way to sample a large area but when you suspect a small deposit that may take up a ½ acre or less it can be cheaper to use a backhoe or an excavator depending on if you have one or how much they are to rent. I had one small deposit that I rented a local backhoe for to sample and check depth on a ¼ acre are. It cost $210.00 a day to rent a backhoe and I spent 2 days there. So for $440.00 (and that doesn't count my time of course), it was cheaper for that discovery to just rent a backhoe to make sure that the gold was there. I have done this a few times on small deposits and sometimes you make out and sometimes you don't. But for under $500.00 you can quickly find out what is going on, the type of soil, boulders, barren dirt depth, etc.
I found this pdf you can check out - http://137.229.113.30/webpubs/usbm/b/text/b356.pdf

 

[Nitric]

When they survey the deposit, it's just that, it could be ½ a gram per yard 20 feet deep. That doesn't include the 17 feet of barren soil above it. Drilling a large deposit is the best way to sample a large area but when you suspect a small deposit that may take up a ½ acre or less it can be cheaper to use a backhoe or an excavator depending on if you have one or how much they are to rent. I had one small deposit that I rented a local backhoe for to sample and check depth on a ¼ acre are. It cost $210.00 a day to rent a backhoe and I spent 2 days there. So for $440.00 (and that doesn't count my time of course), it was cheaper for that discovery to just rent a backhoe to make sure that the gold was there. I have done this a few times on small deposits and sometimes you make out and sometimes you don't. But for under $500.00 you can quickly find out what is going on, the type of soil, boulders, barren dirt depth, etc.
I found this pdf you can check out - http://137.229.113.30/webpubs/usbm/b/text/b356.pdf

I'll probably never have these problems or have to worry about a large deposit where I would need more than a pan and High banker. lol But if someone were to put the information in front of me, of a good area? I wouldn't know how to read it or how they came up with the information presented. So, out of curiosity I was trying to understand big, then work my way backwards. It sound like a waste of time, but I have a lot of time on my hands right now.

Thank you for the link! I'm going to read that now.

 

[Clay Diggins]

Good points Reed. The backhoe method will get you much more accurate figures than drilling. Drilling is really only done for large placer deposits or area sampling.

The nugget effect is very hard to overcome. As much as 50% of drill samples need to be thrown out in your calculations making drill sampling much more expensive on placer deposits. The results are always rather suspect with drill methods when sampling placers. It's not voodoo science but the reliability depends largely on who is doing the analysis.

I've got to disagree with you on the overburden statement Reed. Any material that needs to be moved to recover the gold is a factor in estimating yield. That 17 foot of overburden takes that 1/2 gram down to .08 gram value on the deposit. There is a big difference between calculating lode and placer deposits. See SEC regulations and CIM standards. All placer deposits are calculated in situ with overburden.

Here's a good ALLUVIAL EXPLORATION & MINING primer from Minelinks on the various methods of sampling and their relative uses.

Heavy Pans

 

[Nitric]

Good points Reed. The backhoe method will get you much more accurate figures than drilling. Drilling is really only done for large placer deposits or area sampling.

The nugget effect is very hard to overcome. As much as 50% of drill samples need to be thrown out in your calculations making drill sampling much more expensive on placer deposits. The results are always rather suspect with drill methods when sampling placers. It's not voodoo science but the reliability depends largely on who is doing the analysis.

I've got to disagree with you on the overburden statement Reed. Any material that needs to be moved to recover the gold is a factor in estimating yield. That 17 foot of overburden takes that 1/2 gram down to .08 gram value on the deposit. There is a big difference between calculating lode and placer deposits. See SEC regulations and CIM standards. All placer deposits are calculated in situ with overburden.

Here's a good ALLUVIAL EXPLORATION & MINING primer from Minelinks on the various methods of sampling and their relative uses.

Heavy Pans

Awesome! Now, my brain will be smoking! Hope, there is enough oil up there!!!! After I get a basic understanding of this stuff, I'll try to go backwards,and learn the history.

Thanks again! To everyone!!