For the past 13 years, it has officially been named BHP Billiton but once the world's biggest mining group flings its "non-core" assets, announced today after months of speculation, it is more likely to resemble the BHP it once was.

For most of this year, under the guidance of recently appointed chief executive Andrew Mackenzie, BHP has been engaged in what it has dubbed a "simplification" process; a euphemism for working out a plan to hive off the company's unwanted assets either through a sale or a split.

Not surprisingly, it has opted for a split, with shares in a new company to be handed gratis to existing Australian and South African shareholders.

With almost every resource company around the globe engaged in the same process, it clearly was not a seller's market.

And given the size of the resources portfolio BHP now wants to shed, there were precious few buyers with sufficient cash.

Along with the southern African assets it inherited through the 2001 merger with Billiton, the new spun-out company will include BHP's Australian nickel assets including the Mt Keith, Cliffs and Leinster mines and associated infrastructure with the Kalgoorlie smelter, Kambalda concentrator and the Kwinana refinery.

The nickel division alone – dubbed Nickel West – was being hawked around the market for months with a price tag of $800 million.

Also included will be the Cannington silver lead mine in Queensland along with its South African thermal coal and aluminium assets and its Australian bauxite, alumina and manganese operations.

But the split will be no simple task. With the company now occupying a dual listing in London and Australia, the demerged company will be spun out only to Australian and South African shareholders with reports that London-listed shareholders will be compensated through a cash return.

For years the company has portrayed itself as a disciplined owner of what it describes as long-life tier one assets.

But the 2001 merger with Billiton saddled it with a portfolio that held greater risk than many investors would have liked. The merger was seen as a great deal for Billiton and less so for BHP.

The new slimmed down BHP will comprise four pillars; its huge iron ore division focussed on West Australia's Pilbara, its coal assets in Queensland, the petroleum business in the Gulf of Mexico and Texas and copper operations at Escondido in Chile. A potential fifth pillar is potash in Canada.

BHP has a long history of reinvention. Born as a mining group in 1855 in Broken Hill, for generations it was identified as the country's biggest industrial company, with steel mills in Newcastle, Port Kembla and Whyalla that defined the identity of the nation.

Newcastle was shuttered in 1999 and the Port Kembla and Whyalla were demerged into separate companies, Bluescope Steel and OneSteel.

If there was any emotional attachment to those assets, it has long since evaporated given both groups have struggled to adapt to the changes sweeping through the Australian economy.

During the 1980s gold rush, BHP assembled a massive portfolio of gold mines which it later spun out into a separate company called, unsurprisingly, BHP Gold.

Those assets later formed the bulk of what now is Newcrest, which has been the subject of controversy and massive losses in the past two years, since the plunge in the price of the precious metal.