Geology & GeoMetallurgy

Geology & GeoMetallurgy 2017-04-04T06:58:01+00:00
  • To participate in the 911Metallurgist Forums, be sure to JOINLOGIN
  • Use Add New Topic to ask a New Question/Discussion about Geology and Geometallurgy.
  • OR Select a Topic that Interests you.
  • Use Add Reply = to Reply/Participate in a Topic/Discussion (most frequent).
    Using Add Reply allows you to Attach Images or PDF files and provide a more complete input.
  • Use Add Comment = to comment on someone else’s Reply in an already active Topic/Discussion.

Biased sampling for exploration (4 replies)

1 year ago
Oberfuhrer 1 year ago

In exploration the goal is often to deliberately bias the sample to find trace concentration of target minerals. The classic example is panning concentrates in search of diamond indicator minerals. I'm interested in comments from members on the more successful stream sediment and soil sampling methods they have used for targeting base metal and gold deposits.

John Koenig
1 year ago
John Koenig 1 year ago

The goal (in metals exploration) is more commonly a consistent sample, rather than a biased sample in my opinion. This is because you need to be able to compare the analytical results across a large number of samples to identify the anomalies. We may sieve to a particular fraction in soils for example, to avoid fractions that may be foreign to the site (e.g. windblown material), but this is in order to raise the concentration target elements above the analytical detection limit. If the sieving doesn't produce a consistent sample, such as when the soil type changes dramatically, then it's value starts to decline <--- unless you level for soil type effects of course :)I don't see that many panned cons taken for routine analysis as such, more for the ability to identify key phases or give an indicative result that some mineralization may be around. That's a significant difference in application.

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

I was on a sampling crew that sampled over the Gerrit Canyon, Snow Canyon and North Fork/Big Springs, Nevada gold deposits. Our sampling was excellent, the QC/QA was spot on, but our company missed those deposits.

When the results would come back from the labs, the Project Geo would take a red pen and arbitrarily cross off all the Au numbers he "felt" were too high or aberrant.

Later, as a consultant, I had the opportunity to re-sample the North Fork/Big Springs area once again. We sampled on 60m centers over a 15.5 square kilometer area.

That time, the Project Geo was upset and disillusioned with our work as very few of the assays returned Au. However, It was pointed out to him the As anomaly was several orders of magnitude higher than the regional norm. A new 'model' was put into place and a major gold discovery was made.

We utilized a very standard practice of consistently sampling from the "C" Zone, field screening the samples to a -40 mesh after which the lab would screen to a further -80 mesh and then assay with either Fire or AA or both.

Quite often, the methodology of sampling is not the most important factor in discovering a blind ore body, but rather, the interpretation of the results against an unworkable model can be the 'killer' element.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

You summarizes the key points effectively, and as points out it's all about pattern recognition and contrast. For actual information and case studies (albeit with an Australian flavor), check out the CRC LEME website which summarizes the decades of work by people like Ravi Anand and Charles Butt. There are some great documents about how certain elements behave in the regolith and therefore sample selection criteria.

I can't put my name to any discoveries, but I think I can say the team I worked with in WA in the 1990's missed a few because of our lack of understanding of the importance of putting assay results in a landform/regolith context.

1 year ago
Unterstarm 1 year ago

Thank you for a very interesting discussion. About diamonds and panning I think, it is matter of a standardization of concentration method. It can be manual panning with people who pan the same, better one person or a separation device. But at the end Geologist who analysis the data is the most important link in the chain as it was depicted by. That is why using semi quantitative analysis can be better than precise and expensive techniques.

Please join and login to participate and leave a comment.

BUY Laboratory & Small Plant Process Equipment

We have all the laboratory and plant equipment you need to test or build/operate your plant.

ENTER our Mining Equipment' Store

We Sell EQUIPMENT for all types of Mineral Treatment PROCESSES and Laboratory Testing needs

Have a Mineral Processing QUESTION?

Come in, ask your question

911Metallurgist Community Forums

Talk to other metallurgists and be helped.


We can IMPROVE ALL PLANTS / Mineral Processing Engineering & LABORATORY Ore Testing

911Metallurgy Engineering

Contact us for process engineering, metallurgical investigations, plant optimization, plant troubleshooting, needs. WE “FIX” METALLURGY.