I've been following this for a while. The explanation originally made for the precious metals inability to be extracted by conventional methods was due to relativistic effects of the motion of electrons in the gold and platinum.
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This still remains the only reason put forward so far. My training is in physics and when I looked into this a long while ago I found that relativistic effects in chemistry can be considered to be perturbations, or small corrections, to the non-relativistic theory of chemistry and I don't seem like likely candidates for the problems with the assaying . Small perturbations mean small energies.
They will need the best chemists they can get as these exceptional precious metal grades can't be seen in visible light under any magnification. Esh