There is nothing overly obvious here. Table 1 are seperate rock...

There is nothing overly obvious here.

Table 1 are seperate rock and slag values for each sample, obtained using combinations of different numbers of fluxes (metallurgical techinques)

Table 2 are the grades of the slags from these samples determined by a standard fire assay technique.

All the grades have supposedly been accurately back calculated to the original sample size and all come from a well homogenised bulk sample of fresh gabbro (now dolerite).

Curiously the flux combination which is most sussessful at recovering the precious metals is also the one that left the most gold in the slag. You’d sort of expect the more efficient/successful method would leave less gold in the slag. It almost feels like the more flux components that are added the more gold appears. It would be interesting to know the quantities and types of fluxes used, the smelt temperatures required and the amount of nitric acid required per unit weight of sample being refined.

Also on the use of nitric acid.

Traditionally only a combination of nitric acid and hydrochloric acid can dissolve and precipitate out gold, neither acid can do it by its self.

You can read about dissolving gold here

https://en.m.wikipedia.org/wiki/Aqua_regia

I suppose the strange and unexplained “ionic” gold in these rocks has changed the steadfast rules and that’s why the samples can’t be assayed by conventional means which often also involve an Aqua regia digest.Esh