The mining industry is creating a dotcom-style bubble of companies with dizzying market valuations but which make no money, one of the sector’s most seasoned figures has warned.

Mark Bristow, chief executive of Randgold Resources, a gold miner with a market capitalisation of £1.8bn ($3.5bn) and a significant presence in west and central Africa, said the soaring valuations that have tracked the commodities boom ignored whether companies were likely to turn a profit.