Rio Tinto Group, the world's third-largest mining company, has made a A$3.5 billion ($4.53 billion) takeover proposal for Riversdale Mining, which is developing coal mines in Africa.

Kiwi diamond buyer Ange Hardy went up against the big boys to secure the rare 22-carat white diamond which Hollywood celebrity Kim Kardashian will brandish on her finger on Tuesday.

NZ oil and gas exploration will get a substantial boost in government resources, including funding to chase deep-sea methane hydrates that have yet to be commercially exploited anywhere in the world.

Nearly 2000 engineering and manufacturing workers have agreed to accept a 3 per cent pay rise this year and the same again next year.