taseko mines ltds shares rallied tuesday after the mining company said it would partner with mitsui  co to develop tasekos florence copper project in arizona a development that would almost double the companys annual metal production when complete in morning trading shares were 14 higher at 195 canadian dollars us143 narrowing the yeartodate drop to 25 the us arm of mitsui has committed to an initial investment of us50 million with the money earmarked for construction of the commercial production facility at florence taseko said the investment would be in the form of a copperstream agreement on roughly 27 of the copper produced at florence mitsui has an option to invest a further 50 million for a 10 equity stake in florence exercisable within a threeyear period after completion of construction of the commercial production facility the canadian company said adding that if mitsui exercises the equity option the copper stream will terminate as part of the agreement the company entered into a contract for 81 of the copper cathode produced at florence in the initial years of production taseko said it said the companies will use this period to develop sales channels in the us leveraging mitsuis existing us cathode trading business taseko which is majority owner and operator of the gibraltar openpit copper mine in canada expects construction of florence to begin next year