Rio Tinto Group’s best profit in three years and a record dividend is yet another sign that miners are reaping the benefits of a surge in commodity prices.

Yet the sheer size of Rio’s cash flow is starting to raise another question: how else will the world’s second-biggest mining company invest all its money?

In December, Rio approved spending $368 million to continue the future development of the Resolution copper project in Arizona, a joint venture with BHP Billiton Ltd., according to the statement today.

Shareholders may be willing to support Rio if it moves to add a different commodity to its portfolio -- mainly based around copper, iron ore and aluminum, according to a report from UBS Group AG.

Quimica & Minera de Chile SA, one of the world’s top lithium producers, people familiar with the matter said last month.

“It’s a very consistent message and strategy which shareholders will like,” said Richard Knights at Liberum Capital Ltd. “Given the multi generational nature of their asset base, mainly iron ore and aluminum, they can keep this up a long time.”

Investec’s Hillcoat said it’s unlikely that Rio will embark on any “multibillion-dollar expansions” to chase M&A growth or pay a premium for other commodities, such as copper, given the industry’s history of overspending.