Whitehaven investors have punished the company for cutting its expected output after issues at its Narrabri coal mine.
The ASX's best performed coal pure play miner suffered a reversal of rare proportions in recent times on Thursday when 6.18 per cent was sliced from its share price.
The slump came after the company's quarterly update showed that underground mine stability issues at its Narrabri coal mine had lifted operating costs and trimeed its previous production guidance by between seven and nine per cent lower.
"Reflective of the experiences at Narrabri during the December quarter, saleable coal production guidance for [the financial year] has been reduced to the range of 20.5 to 21 million tonnes," Whitehaven said in a company statement.
Whitehaven recorded a massive jump in its coal sales, up 16 per cent year on year, rising from 10.278 million tonnes to 11.88 million tonnes.
Much of this was driven by continued strong performance at its Maules Creek mine, where coal production was up three per cent compared to the previous quarter, and expected to reach 11 million tonnes for 2018.
Whitehaven's Narrabri operations, however, dropped 12 per cent in its coal production levels for the December quarter, caused by the underground coal mine's roof needing increasing levels of support.
As a result, Narrabri's production outlook has been lowered to between 6 and 6.5 million tonnes for 2018, and it forecasts operational costs to increase by around $2 per tonne of coal.
The second half of the year is forecast to be stronger, as Whitehaven reopens its Sunnyside open cut mine, which has been shut since November 2012.
The miner also took control of its Tarrawonga joint venture, acquiring its partner Idemitsu's 30 per cent stake in the mine to take Whitehaven's ownership up to 100 per cent.
Whitehaven was unable to give a definitive date for the start-up of its Vickery coal mine, putting its operation around the point when its Maules Creek mine ramps up to its full 13 million tonnes per annum capacity.
Fat Prophets analyst David Lennox said Whitehaven had seen such a huge drop in value as it had been "priced to perfection".
"Unfortunately, they didn't deliver that perfection, so the share price was somewhat crucified. Perhaps they didn't quite convey the Narrabri issues to the market enough prior to these results," he told Fairfax Media.
Whitehaven opened the day's trading at $4.48, rapidly falling to $4.37 before charting a recovery to sit at $4.46 by mid-afternoon.
Despite this fall, Whitehaven is still at one of its highest trading points in five years.
