Thanks for checking, I need to be super careful here with the target on my back lol. Sometimes it's looking you right in the face but you can't see it.
A lab error is the obvious explanation for the HA067 sample outlier, and why the company asked the lab to re-test their results. The duplicate sample next batch as flagged should clarify that situation. Errors are much more common in standard THM lab assay in my experience than mineral assemblage analysis. The process is completely different, a lot more analysis of many individual minerals means that simple translation or data errors are generally picked up and corrected during a re-test. Like so much of the bull/bear arguments, time will tell.
As per my earlier post, a physical sorting process is unlikely to separate so completely only the Ti-mag and Low Ilm Ti-mag from the other heavies. I'm thinking perhaps extreme weathering alteration that strips a lot of iron from the Ti-mag might explain why it all reported to the Ilmenite phase? A bit of digging around and that explanation starts to look a possibility, especially the way the numbers have been reported. Weathering above the water table near the surface can strip Ilmenite of Fe leaving a higher TiO2 % in the residual, altered ilmenite grain crystal structure. Thus a primary Ilmenite with TiO2% in 40s increases with weathering and right conditions to TiO2% in 50's, then altered ilmenite in the 60's, then to Leucoxene between 70 and low 90's.
Magnetite (Fe3O4) can oxidise to magheamite (Fe2O3), also losing Fe and increasing the TiO2 content in the case of Ti-mag. Given we know ilmenite exists as a an inter-growth in the Ti-mag, it's possible in extreme weathering that TiO2 content may increase by >10% for lowIlm Ti-Mag and Ti-Mag. Certainly in low-slime sand very near the surface weathering from continuously percolating water and exposure to air, the alteration process is sped up and the assemblage can look quite different. In older deposits, surface samples are notoriously elevated in altered ilmenite and lower in primary ilmenite compared to the majority of the deeper sands for this this reason. Although this overprint doesn;t usually go very deep it can under the right conditions (eg a relic drainage area where percolating waters were greater than elsewhere).
I went back and looked at the July 2019 assemblage results release, done on three surface samples in run-off concentrations collected across Corridor. The bulk of the ilmenite was highly altered ar around 70-85% TiO2 which is well and truly into the altered ilmenite phase.
Last weeks assemblage results release defined ilmenite as between 43-55% TiO2. 13th July 2020 KM mineral separation work assemblage product release reported an ilmenite between 46-50% TiO2. I caclulated after removing the Chromite the ilmenite would be ~53% TiO2. This is a KM deposit wide sort of result and proves that highly weathered/altered surface samples do not materially impact of the deposits overall assemblage features.53% vs 70-85% TiO2 are chalk and cheese. Now I wondering why last years surface samples had much lower Ilmenite % than the latest HA067? The answer is in changes to grouping intervals for the reported assemblage. Below is the July 2019 release showing Ilmenite% very similar to Corridor 1 as per Southern Mining Corporation annual report 2000. Note the ilmenite = altered ilm (70-85% TiO2) and ilm (50-70% Ilm).
Everything below 50% TiO2 was deemd "highly likely to be lower-TiO2 ilmenite".
In last weeks assemblage update the company has chosen to change the definition of "ilmenite" to now include everything above 30% TiO2.
So how much of the 'weathered and altered Ti-mag" has now reported to the "ilmenite" fraction with a lower 30% TiO2 cut-off? From the KM MRE report we know that the Low Ilm Ti-Mag already had a range generally between 20-30% TiO2. Obviously heavy alteration and Fe removal will lift this phase into the 30-40% TiO2 bracket and thus become redefined as "ilmenite".
Further, from the July 13th assemblage product release we know that the Ti-mag representing 32% of the HMC has a TiO2 of 15%. That product may well contain a considerable amount of magnetite with no/low TiO2 bring down the average TiO2 levels to 15%. Maybe on a grain by grain basis a 15-20% TiO2 Ti-mag has been upgraded through heavy alteration to >30% TiO2 and also thus reported as the new "ilmenite'?
Although an extreme amount of weathering/alteration such that virtually no low ilm ti-mag or ti-mag exists anymore within HA067's 10.5m composite , it makes more scientific sense than a physical sorting separation. Change the grouping TiO2 cut-off definition enough and sure, you can make it all 'ilmenite'. By the definition of a 30% TiO2 cut-off the three surface samples form July 2019 would be in the 60's maybe. A more reasonable surface alteration effect is seen in sample HA064, where rather than completely disappearing, the low Ilm Ti-mag halves to 5% and the Ti-Mag halves/thirds to 7%.
Before anyone gets carried away with the "weathering upgrade effect" keep in mind the ilmenite will also be highly altered, low recovery, and likley high in contaminants (residual Ca, Mg, Sio2, U, Th) that get left behind and concentrated in the altered ilm grain. Also, the mine and Dry Plant are built to process and sell a consistent quantity of product as delivered by a large mining operation. Small amounts of highly altered surface assemblage don;t work in this context and don;t usually add up to meaningful quantities. As we saw at KM, the july 2019 surface samples are unrecognisable in the context of the global MRE.
(20min delay)