Coal was first reported in the Nanaimo area in 1849. The Nanaimo Coalfield was developed and more or less depleted between 1852 and 1953, during which time a total of 49 megatonnes of coal was produced.

Production in the Nanaimo Coalfield was from three major seams: the Wellington, the Newcastle and the Douglas. The Wellington seam was worked in the Wellington field, the East Wellington field (includes the Chandler/East Wellington 092GSW030 and Wakesiah 092GSW040 operations), the Harewood mine (092GSW033) and further to the south, the Extension field (Extension No.1 thru 3 092GSW028, Extension No.4 092GSW053, Extension No. 8 092GSW042, Beban's 092GSW026, Old No.1 Slope/Vancouver 092GSW027, Extension Prospect 092GSW036, White Rapids 092GSW043). The mines are separated by faulted strata or areas where the seam thins to unprofitable thicknesses. The total workable area was 19.3 kilometres long and averaged 1.6 kilometres in width.

The main Wellington seam (No. 1) occurs in the Northfield Member at the base of the Lower Campanian Extension Formation of the Upper Cretaceous Nanaimo Group. The coal is commonly underlain by sandstone and overlain by conglomerate of the Millstream Member. Shale partings are common in the main seam and thickness is extremely variable, ranging from 1.2 to 2.13 metres, due to minor folds, faults or bands usually in the roof (the base of the overlying Millstream Member is often a scour surface). The average thickness is 1.9 metres inclusive of minor dirt bands. The floor is marked by a distinctive rooty bed. The main seam, high volatile bituminous in rank, was the main producer of the Wellington field coal.

Minor workings were established on three upper seams designated the Wellington No.2 or Little Wellington, Wellington No.3 and Wellington No.4. These rarely exceed 0.60 metre in thickness and lie above the Wellington at intervals of 10.67 metres, 18.29 metres and 22.9 metres, floor to floor.

The strata strike northwest and dip towards the northeast (approximately 10 degrees). To the south and west, the beds are cut off by a northwest-southeast trending normal(?) fault and a number of broad northwest trending folds occur in the coal bearing formation to the north and east.

The area encompasses the Wellington Colliery workings, the Wellington No. 9 mine (092F 312) and the Northfield mine.

The Wellington field, northwest of Nanaimo, was initially discovered by Robert Dunsmuir in 1869 and mining operations began in 1871. Production for 1871, 1872 and 1873 was 134,682 tonnes.

The Northfield Mine, immediately east of the Wellington Colliery was worked in the Wellington seam from 1889 to 1895 and later these workings were used by the Dunsmuir interests to enter an area of the upper Wellington seam. The Wellington mines were exhausted near turn of the century and activity moved southwards to the East Wellington and Extension fields.

The last production of the Nanaimo Coal fields was from the Loudon No. 6 mine, which was worked until July 1968. The old workings were also mined as the Carruthers and Wakelem No. 3, the Stronach No. 2, and others.