Re grade,
A lot depends on where you view the mining step as ending and the benefication step as beginning. The starting position for E25 is that ore is in the ground is 7.6%. This figure is inclusive of all the overburden and other surrounding materials that need removing before you get to Mn containing rock.
I'm not sure exactly what S32's GEMCO mine equivalent is, but current mining is lower than this. GEMCO's strip ratio in 2020 was 5.4:1 (a ratio wasn't reported in 2021). They had a starting ore grade 7.0% inclusive of all rock/dirt needed to be removed to reach this. Within this there were 5.4 parts had no Mn and one part with 44.6% Mn ore. (5.4*0%+1.0*44.6%)/6.4 = 7.0%. The ratio could be lower if rock lost in benefication was not captured in the strip ratio.
Relative to all the clay, dirt and rock that needs to be removed to access the ore, E25 has a higher grade than GEMCO currently does!!
What happens nextE25 has a really low strip ratio and gets to 10.3% ore before washing and benefication
GEMCO has a high strip ratio. High grade ore is recovered that is improved further by washing and benefication. I'm not sure what grade it is after washing but before benefication.
What if E25's washing was considered a mining activity not a processing activity?Washing ore has some characteristics more akin to the mining step than the benefication processing step. The nature of the Mn containing ore is not changed, but surrounding non-rock (clay) material is removed. One definition of overburden from Google is "Overburden is the rock or soil layer that needs to be removed in order to access the ore being mined."
E25's log washer is very close to meeting this overburden definition as it relates to removing the layer of clay that needs removal in order to access the Mn containing ore. If washing the clay off the ore was considered a mining overburden removal step, E25 would have the same containined Manganese metal in its reserves and resouce estimates. The volume of Ore would drop and the grade would increase.
[email protected]% would become 19.1Mt @ 27.3%. If E25 was publicising itself as having a 19.1Mt resource at 27.3% and a reserve of about 100Mt @ 26.3%, no-one would be saying E25 has a low-grade resource. All that would have happened is the log washer would be part of the ore extraction mining step. But that is exactly what the underlying ore situation at Butcherbird is. A lot of clay surrounding high-grade ore.
IMO E25 would have better recognition as a 100Mt resource @ 26.3% than 263Mt @ 10.0% despite both being 26.3Mt contained Mn. As shown below, its basically shifting the "clay removed through washing" step to sit up alongside the "Overburden removal" step
Its how the story is sold. E25 have gone for big and lower grade. There is an alternative of still very large and high grade. Most of the upgrade from 10% to circa 33% is not the benefication process but simply washing the Mn containing ore of surrounding clay.
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