Geology & GeoMetallurgy

Geology & GeoMetallurgy

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inconsistency of grades (3 replies)

4 years ago
louwrens 4 years ago

Hi all we have a mining operation, and our lab cannot explain the fire assay results provided, we did quite extensive test work on the ore and have received inconsistent results.

Once the ore is delivered to our site the ore tests at 40-60 g AU per ton this will be three samples from a 10 cube truck. 

This obviously makes as hell excited, however a week later the same pile will be sampled and a consistent grade of between 3-6 g/ton is tested.

What can the cause of this be is there a possibility of chemicals that someone can throw on the ore to give false readings? 

Thanks in advance for assistance herein.

4 years ago
Nurettin 4 years ago

Are all tests fire assay?

what about S content and types, Cu(I), feldspats?

small but rain effect?

Craig M
4 years ago
Craig M 4 years ago
1 like by David

What you have described in your initial post, was an effort at 'grab' sampling. It was also practiced on some of the most difficult gold ore possible, high grade ore. In order to obtain results that are statistically representative, and perhaps reproducible, you would need to follow standard practices and sampling theory.  You will find that the errors in sampling are greatest early in the process, such as at the drill, or in the mine (ie., truckload sampling?). Standard practices would have you reducing the particle size, applying these particle sizes through theory and taking representative samples, timed samples, using geometrically designed and installed samplers. There are also some chemical/elemental components that can interfere with fire assay, and there are frequent pitfalls throughout the size reduction, sampling, blending efforts.

4 years ago
Siddiquf 4 years ago

Representative sampling of broken ore is always problematical. Inconsistency in your case may simply be due to the sampler picking up the well mineralized pieces selectively in the first sampling.  

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