The copper concentrate is on the low end of acceptable copper percentages for 'attractive' smelters. Context in how the smelters make their money is required here, to understand this. Generally, the smelter charges a fee for services for treatment (TC) and refining (RC). PGE's in copper concentrates are attractive to copper smelters (as are gold and silver credits) because the smelter tends to (in broad terms to make the point; the real mechanism is a bit more complex) 'take' the first couple of grams of gold as a refining charge. Therefore, if your copper concentrate has low precious metals, you tend not to get high 'payability' of the precious metals.
So, a smelter will take a PGE rich copper (chalcopyrite) concentrate and skim the first couple of grams off the top for themselves, and pay the company for the rest. This will be attractive with Pd, Pt and Au, and somewhat so with Ag.
The problem being, the PGE's are an incredibly variable set of minerals (see this release), and in this case the PGE mineral assemblage has some potential embuggeranes welded into it, being a tin-bismuth-arsenide assemblage. Arsenic is a penalty (again, above a certain amount in the concentrate) that the refinery charges you to deal with, and whilst I am not familiar with the specifics of smelting palladium-tin alloys and palladium arsenides, it's not quite as straightforward as sperrylite.
So, you have a moderate grade copper concentrate (25% is average, 27% is good, 29% exceptional) with good prospective payability of Pd, reasonable Pt, and normal Au payability. Note also that the grade is variable (Figure 2) between two populations; AM78-51, AM78-52 and AM78-50 provide the 20-27% Cu concentrates, the remainder provide lower grade Cu concentrates in the 15-20% range, which will be less attractive.
Nickel wise, 12% Ni is not exceptional, but it's good. Again, the various composites have wildly different Ni tenor (%Ni in 100% sulphide), representing the different ore surfaces. There's two populations; low-grade pyrrhotite dominant stuff like AM78-48 and AM78-49 running 0.15-0.19% head grade and producing poorly payable low grade nickel concentrates at 6-8% Ni and low recovery; and higher grade, more pentlandite rich surfaces at 60-80^ recovery and 12-18% Ni in concentrate.
Ultimately this will be dealt with by blending, assuming the stoichiometry and mass-balance allows blending to a specification. If the Gonneville is dominated by too much sub-grade, pyrrhotitic gumf, then there will be mountains of unsaleable 6-8% Ni concentrates, and the oxidation or vat leaching option will have to come on to the table versus direct sale for smelting.
Basically, this is going to take a couple of years to sort out, but the box is ticked ahead of the maiden JORC resource.
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