Assaying, Microscopy, Mineralogy & XRF/XRD

Assaying, Microscopy, Mineralogy & XRF/XRD

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Gold particle size distribution in Au deposits (2 replies and 1 comment)

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el_francis
6 years ago
el_francis 6 years ago

Hi there, I'm completely new to 911 Metallurgist, but maybe someone here can help me out! 

I'm looking for studies that characterize the gold particle size distribution in different geological deposit types (I'm a geologist).  I would like to know how the size distribution of Au particles varies in different deposits, so that we can better target our Au exploration programs. 

We are looking at doing large-scale till sampling programs in the Canadian Shield where the dominant deposits type is orogenic Au (quartz-carbonate shear-hosted veins with Au).  The glaciers came along and milled everything up in the last ice age, and before sending the till samples for analysis they are sieved to a certain size fraction based on standard sieve sizes.  I'm trying to find out what's the best sieve size, which to me, would be determined by the Au particle size distribution (for free gold), and also the mineralogy and where the Au occurs in most of these deposits.  

I've been looking around in some metallurgical sections from 43-101 reports, but they don't really get to the data that I would like (most are focusing on optimizing grinding size for the economics, but they don't really touch on the Au particle size distribution).

Where should I look for this information? Mineralogy reports? Is there anywhere I should be looking in the public archives i.e. 43-101's, scientific journals, etc.?  

Many thanks for any help, 

Francis

J
goldivanti
6 years ago
goldivanti 6 years ago
Like

1

Different projects may make different reports or studies. One file that I have is the one you may find on this link: https://duckduckgo.com/html?q=british+geological+survey+review+of+particle+size+distribution+filetype%3Apdf&t=gnu

You could be researching archives of Canadian geological survey, or simply making an inquiry there.

In my opinion, to use studies or reports of other people in your project is hardly to bring some benefit. Your project is specific to the land where you are working. Thus the study shall be made by you, and be specific to such land, including to the layers, depths, veins you are researching.

Practical advice:

First step would be to properly obtain samples, and know how to concentrate gold of all particle sizes properly. Such concentration alone is IMHO expensive, as you must be sure you are not loosing almost nothing, and whatever you are loosing you would need to analyze as well.

Next step would be to classify the concentrates and be sure to know how to obtain proper values. You may use the popular plastic sieves, or US standard testing sieves or Tyler sieves, that depends of your investment range.

Thus:

  1. Proper sampling.
  2. Concentration of material for all particle sizes (required good technology to make sure it works)
  3. Accurate analysis of the losses in tailings after concentration and particle size analysis of it.
  4. Particle size analysis of the gold particles, provided you have good methods to actually recover them.

 

f
el_francis
6 years ago

Thanks for the BGS link, the section on bedrock gold is definitely what I'm looking for, but for a big enough number of deposits to look at things statistically. I would be very interested in any other studies such as this, if anyone has other information.

We don't really have time/money to do a large orientation survey where we would sample all of the different size fractions for Au, and also we would have to use a known deposit, which might not give us data about what could also be around elsewhere on the property (the property is ~60,000 hectares). This is why I would like to look at things statistically, from other deposits across the world, to try to cover all the bases.

D
Deano
6 years ago
Deano 6 years ago
Like

The advice given is spot on, the best method of concentrating the free gold is with a super panner. Look for a lab or test facility which has one.

Always keep in mind that gold which is present as free gold in your circumstance has been milled naturally so that the gold particle sizes will be larger than the original unmilled particles in the ore.

You are probably looking at optical sizing of the gold particles in the concentrates from the super panner.

 

 

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