03/27/2012 04:32 EDT | Updated 05/26/2012 05:12 EDT

Rio Tinto reviewing if diamond assets, including NWT mine, continue to sparkle

MONTREAL - Global miner Rio Tinto is considering whether its diamond operations, including one in Canada, will continue to sparkle in its hands or should be sold.

The company, which operates three diamond mines, including one 300 kilometres northeast of Yellowknife, unofficially encouraged bids in a news release on Tuesday.

"We have a valuable, high-quality diamonds business, but given its scale we are reviewing whether we can create more value through a different ownership structure," said division chief executive Harry Kenyon-Slaney.

He added that diamonds are a high-quality business with growing demand.

However, Kenyon-Slaney said the company was reviewing whether diamonds fit with its strategy of operating large, long-life, expandable assets. Rio Tinto (NYSE:RIO) did not announce a deadline for a decision.

The review could lead to the sale of its stake in diamond mines or an alternative ownership structure.

The announcement marks the second time in recent months a miner has said it is looking at selling its Canadian diamond operations. Late last year, Anglo-Australian mining giant BHP Billiton (NYSE:BHP) said it was selling its stake in two Canadian diamond mines.

Analysts have estimated that the diamond operations could sell for between US$2.4 billion and US$5 billion.

Tony Robson of BMO Capital Markets said the two mining giants face the challenge of generating scale despite rising diamond prices and profitability.

Rio's main diamond assets are mature or located in politically difficult operating regimes.

"Whilst Diavik in Canada continues to be a good operation, it only has around 10 years of life left based upon current reserves," he wrote in a report.

Australia's Argyle mine is moving to underground operations and has been plagued by operational problems and capital expenditure overruns.

The Murowa mine is located in Zimbabwe, an increasingly challenging country to in which to operate politically. The project in Bunder "appears to show positive economics, although its location in India mires all work in bureaucracy."

Robson suggested Diavik partner Harry Winston (TSX:HW) could acquire Rio's 60 per cent stake. While it is debt-free, the acquisition is likely too large "to be digestible without a strategic partner."

"Furthermore, as Harry Winston does not currently operate Diavik, it can be argued that it lacks the necessary in-house mining expertise."

Rio Tinto is one of the world's largest miners, with iron ore and aluminum operations in Canada. Its major products are also copper, thermal and metallurgical coal, uranium, gold and industrial minerals (borax, titanium dioxide and salt).

Its net profit fell 59 per cent to US$5.8 billion in 2011 because of an US$8.9 billion impairment charge for its aluminum business.

Adjusted earnings increased 11 per cent to a record US$15.5 billion.

Rio's diamond production decreased by 15 per cent to 11.7 million carats last year as Australian production fell 24 per cent due to heavy rains. That was partially offset by a three-per-cent increase in throughput but lower grades.