This brings to about US$3 billion the value of mining deals – including its US$1.15 billion friendly bid for Rio Algom and its purchase of a further 56% of the Worsley alumina refinery in Western Australia for US$1.49 billion - struck by Billiton in the past month as it tries to diversify its aluminium-heavy portfolio.

The latest focus of its attention, the Howards Pass deposit in Canada’s Yukon territory, has a resource estimate of 110.5 million tonnes grading 7.7% combined zinc plus lead, with silver and cadmium.

Copper Ridge recently acquired the option to buy Howards Pass from Placer Dome US Steel Group subsidiary Cygnus Mines for C$10 million (A$11.77 million) in staged payments over four years. Placer discovered the deposit in 1977 but never developed it because of its remoteness.

Copper Ridge will commit to expenditure of C$3 million comprising a $2 million concept study and a $1 million initial payment to Placer and US Steel.

The concept study will define the key economic, environmental, geological, mining, metallurgical and infrastructure parameters for development of the project.

Billiton will make a private placement totalling C$200,000 to be used by Copper Ridge to initiate a drilling program on the project, followed by a second placement of C$200,000 following announcement of the successful completion of Billiton’s due diligence review, which is to be completed by October 15.

Following completion of the concept study, Billiton can elect to earn a 50% interest in the Howards Pass property by spending C$5.5 million by November 15, 20002, for the completion of the pre-feasibility study.