A major disaster took place on 16 January 1862 at the Hester Pit, New Hartley, Northumberland. The massive cast-iron beam of the pumping engine fractured and plummeted down the shaft, striking the cage bringing miners back to the surface and trapping those down in the pit. In all, 204 men and boys lost their lives, despite prolonged efforts to rescue them. Many of the casualties were Primitive Methodists; others were Wesleyans or from the Methodist New Connexion. Many held office as class leaders, local preachers or Sunday School teachers in their local church. Evidence was found that prayer meetings were held among those waiting in vain to be rescued. The Primitive Methodist societies at both New and Old Hartley suffered particularly heavily. John Dobinson and his son William, from Seaton Delaval, grandfather and father of the Primitive Methodist minister Matthew Dobinson (1872-1951; e.m. 1899), played a leading part in the recovery of the New Hartley society.
There was extensive coverage of the disaster, both in the secular press and the Methodist Recorder and denominational magazines. Hugh Gilmore's novel The Black Diamond, serialised in the Primitive Methodist Magazine, was published in book form 1889. There is a memorial in St. Alban's parish church, Earsdon. In January 2012 the 150th anniversary of the disaster was marked at both New Hartley and Earsdon.