Yes Esh - all questions worth asking - what happens to the slag...

Yes Esh - all questions worth asking - what happens to the slag and what are the total energy inputs into recovering the gold minus the cost of the silver and copper collectors/reagents and minus the cost of relining the furnace.

You could start a gold recovery business by burning enough actual paper currency and recovering the minute trace amounts of precious metal contaminants on the paper money if you wanted to but it wouldn't be a profitable business..

Jokkes aside - so far it seems that the comapny has developed a non-repeatable method to consume a vast amount of energy and metallic reactants to produce a gold rich slag which then consumes a vast amount of energy and metallic reactants (after relining the furnace) to produce a small golden coloured metallic button of unknown content.

Until they solve some of these chemical mysteries that seem to fly in the face of all known metallurgical science, then they will struggle to convince people that they have a gold mine.