The price of Australian coal has slumped to a three-and-a-half-year low on surging supply, signalling the end of a super-cycle that propelled local miners to record profits and created billions of dollars in wealth.

The benchmark price for top-quality NSW thermal coal has fallen by more than 4 per cent to $US115.51 a tonne, according to GlobalCoal. The price has fallen 23 per cent over the past five months and is below the low of $US116.08 a tonne recorded in February last year.