In 1929 colliery owners on the Northern New South Wales coalfields combined Cause_to_amalgamate as the Northern Collieries Association .

On Thursday 14 February 1929 the mine employers gave Giving their 9,750 employees 14 days ' notice , that they ( the miners ) should accept Agree_or_refuse_to_act the following new conditions : A wage reduction of 12½ per cent on the contract rates , one shilling ( $ 0.10 ) a day on the `` day wage '' rate ; all Lodges must give Giving the colliery managers the right to hire Employment and fire Process_end without regard Know to seniority ; all Lodges must agree Agree_or_refuse_to_act to discontinue Process_end pit-top meetings Social_event and pit stoppages .

On 16 December 1929 about 5,000 miners demonstrated Protest against the introduction of non-union labour into the Rothbury mine by the conservative Bavin government , which had taken over Change_of_leadership the colliery .

The government called in Come_together 70 New South Wales police officers from districts outside Newcastle to protect Defending the colliery and allow Preventing_or_letting the entry of non-union labour .

The Aberfan disaster Catastrophe was the catastrophic collapse Catastrophe of a colliery spoil tip at around 9:15 am on 21 October 1966 .