rio tinto plc said tuesday that it has approved a 55 million investment to start underground mining and expand production at its kennecott copper operations in utah united states the angloaustralian mining company said that it will initially focus on the lower commercial skarn area which is expected to deliver around 30000 tons of mined coppers through the period to 2027 the company said that the first ore is expected to be produced in early 2023 and full production to be achieved in the second half of the year the company added that feasibility studies are also being progressed to extend open pit mining beyond 2032 shares at 0807 gmt were up 870 pence or 19 at 4786 pence