The Construction, Forestry, Mining and Energy Union unsuccessfully tried to save the jobs by arguing for a six-day roster to cut production.

“You've got to wonder and we question the motive of these massive multi-national companies about do they genuinely care about their workforces and their local community,” CFMEU northern mining and New South Wales energy district president Peter Jordan told the ABC on Friday.

A Thiess spokeswoman told ICN she was unable to comment on the matter.

Glencore, which holds 100% ownership at Mt Owen, did confirm that Thiess was implementing operational changes at the mine in accordance with production requirements for 2015.

“The changes respond to the economic challenges facing the Australian coal industry and Glencore’s revised production figures for the year, which will be reduced by 15 million tonnes,” a spokesman told ICN on Friday.

Glencore said the current workforce at Mt Owen was 400 and the mine produced 4.5Mt of saleable coal last year.

All of Glencore’s 2015 Australian production cuts have occurred in New South Wales so far. These have included the late March announcement to bring forward the shutdown of the West Wallsend longwall mine to mid-2016 and its production, job and roster cutting changes at Ulan West which are estimated to have reduced 2Mt of annual production capacity.