More than a blip.

With their diverse asset bases, the planned merger of BHP and Billiton marks one of the more significant developments in what is becoming a rapid consolidation of the world's mining industry. Over the past year, merger and acquisition activity has included Rio Tinto's purchase of Ashton Mining (diamonds), North Ltd (iron ore) and its remaining equity interest in Comalco; plus Anglo American's acquisition of the Australian coal assets of Royal Dutch/Shell and its lead role in the record bid to take De Beers private.

The two companies involved in the latest merger plan ha