Lets frame the overall discussion to get an idea of what we are working with here.
The carbonatite that hosts the mineralisation is a relatively soft host rock. This makes open pit mining feasible and efficient. Added to the fact that we are seeing mineralisation begin on average beginning 30-40m due to the transported cover (fig 2 pg 3 of latest announcement - plus similar figure in previous announcements), this is the first big tick. Bearing in mind that Araxa utilises open pit mining very effectively in their operations.
In terms of mining and the existence of other materials. Carbonatites are significant sources of rare earths. This is why we are seeing these TREO grades at the level reported. 3% is normally the yardstick for when it comes to the economic viability of mining those rare earths. I haven't looked across the announcements but looking at this weeks one, we can see anything from 0.09% to 1.68%. Not profitable in their own right, however as mining credits, surely something that will invite discussion.
Now in order to facilitate that discussion around further credits, the mining technique used to extract the minerals is key. For Niobium, the process for us will involve utilising open pit mining. Depending on the Luni deeps, there may be a transition to underground mining, but that relies heavily on the characteristics of the deposit and economic factors. There really isn't a rule of thumb when it comes to a depth where open pit ends and underground mining starts. Once we get a greater understanding of the geological constraints, then this is a discussion that will begin.
Once the ore is extracted, it will require a concentration process to increase the Niobium content. This includes the typical grinding, crushing and separation techniques that we see across most minerals. The separation techniques often are the ones that help determine the recovery rate that we are looking for (typically 30-70% - see pg 5 of latest announcement). Araxa has a recovery of about 60%. These separation techniques could be gravity separation, magnetic separation or flotation. The metallurgical studies will delve into these, so providing my rudimentary commentary of them will be just pure speculation. There is a great breakdown also on page 5 of the latest announcement which sums up that magnetic separation and desliming will precede a three stage flotation process to achieve a lower grade niobium concentrate. This will then go through a hydrometallurgical step (water based) and a pyrometallurgical step (heat based) to improve purity and grade. This is the step where deleterious elements are removed and will be responsible for dropping our recovery % the most, so we will want to have a little waste as possible to keep the recovery % on the higher end of that scale 30-70% above. This is why the met studies are key, because they will determine how many digits are in front of the $B in our market cap (if we go in the direction that our project suggests we will).
Back to the point of Niobium v REEs. The latter requires far more complex flotation and separation techniques. This is an economic consideration because the higher the TREO content, the more costly it will be to separate it from the niobium. REEs may co-precipitate or co-dissolve with niobium, affecting the purity of the final niobium product. Again, this is something that the metallurgical studies will illuminate. Cast your memory back to AZS in recent times. When their met tests were released with some question marks over a high Iron content, there was a mixed reception to those results. However, once it was demonstrated that the Iron (which is deleterious to lithium) was significantly reduced through further separation testing, Gina Rinehart and Chris Ellison didn't hesitate to sink their teeth into that project. The same principle applies here. In my opinion, we have demonstrated scale, it is the recovery that will get the big boys foaming at the mouth.
Now on the point of Uranium v Niobium. The Uranium can be deleterious to the niobium if it is in high concentrations. What constitutes a "high concentration" of uranium can vary depending on several factors, including the specific characteristics of the ore deposit, the extraction method employed, and the intended use of the extracted niobium. These are all considerations that we are too early on the journey to really answer. Also, the uranium may be present in niobium ore in various forms, including as uranium oxides or uranium-bearing minerals. We don't have this information yet, so no need to delve into further speculation. If we do have to separate this uranium from the niobium we may look into heap leaching, in-situ leaching, or the cheapest and best option being solvent extraction. It would be a dream for us to have solvent extraction as the preferred method because it is the cheapest and most efficient (using simple organic solvents) and is also commonly used when separating niobium from tantalum.And guess what our table shows in numerous announcements Ta2O5 (tantalum oxide). Economic grades for tantalum start at around 0.03% or 300ppm. We are seeing grades up to 209 ppm (only in the most recent announcement - I didn't cross check the others). Now, of course niobium does not exist in a vacuum and many elements co-exist within any given host structure. This is why we are seeing recovery rates fall as more complex separation techniques are employed. I wish I could comment on the deleterious nature of these other minerals, however on my uneducated reading it does appear that the tantalum can be cheaply separated from the niobium, and the uranium is super low. Both of these point towards solvent extraction. But I will be cautious not to succumb to confirmation bias when making that assertion because the REE extraction as seen above can be a complicating factor. That is where the cost benefit analysis will be conducted when determining how much purity we are willing to sacrifice in order to take advantage of those REE credits. And who better to help in making this decision than a chap by the name of Clovis Sousa, our resident "Niobium Processing Advisor."
What I can say with confidence is that if we start to hear discussion of solvent extraction in the met studies and low incidence of deleterious elements, then we could be looking at a far simpler and cheaper separation process. And you can throw away all your bollinger bands because the only bollinger you'll be hearing is the pop of the champagne bottle as you celebrate your new found wealth.
TLDR: Wait for the met studies to answer whether other materials outlined in pp. 9-10 of the most recent announcement will materially affect the niobium recoveries and if they are deleterious in any way.
Good luck to all and hope this helps!
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