RTR have only published 3 partial sections that clearly show a...

RTR have only published 3 partial sections that clearly show a significant grade reduction of the Zn-Pb mineralised zone above 60m depth (which is taken to represent the depth of complete oxidation). Sulfide minerals (e.g. sphalerite & galena) appear greatly remobilized (leached away) above this depth. The transition zone (partial oxidation due to fluctuations in groundwater levels) may extend well below this level and some of the elevated grade near the oxidation front may in fact be an enrichment of Zn-Pb leached downwards.

Fine-grinding and sulfide flotation would likely be used to generate separate saleable zinc and lead concentrates (~50%+) and any increased oxidation state would be expected to reduce recoveries of sulfide minerals. Minerals with a coating of rust don't froth well!

Metallurgy will be tricky when dealing with alternate partly-oxidized recovery techniques creating the need for more plant CAPEX to add to the expense of the mine prestrip to remove the top 60m. Not insurmountable, just added upfront costs and a reduction in % recovery overall.

This is quite different from conventional CIL gold treatment where softer, oxidised ores with decreased sulfide species benefits overall gold recovery.

P

@V8 whilst giant deposits at Broken Hill and McArthur River are mostly mined out many others are still in production or yet to be mined. Hermosa is just starting up in the USA!