The Sydney Coalfield is located on the northeast coast of Cape Breton Island (see map), where coal-bearing rocks extend 50 km (21 miles) from Cape Dauphin east to Morien Bay. These rocks extend nearly to the south coast of Newfoundland and more than 98% of the coalfield lies beneath the ocean. The coal can be mined as far as 6 km (3.7 miles) offshore, but the seams have been identified in bore holes 40 km (25 miles) from the land.

The Sydney Coalfield hosts the largest coal resource in eastern Canada and in recent decades has been the centre of coal mining in Nova Scotia. Most of the province's electricity is generated from the coal mined there.

Fossils

Many fossils from the Carboniferous Period have been found in the shales and sandstones overlying the seams of coal in the Sydney Coalfield. In some cases, the trunks of extinct trees such as Sigillaria sp. and Lepidodendron sp. still stand upright above the coal. Impressions of fern leaves, bamboo-like Calamites sp. and other plants are often found. Beneath the seams large roots called Stigmaria sp. are commonly encountered. It was the consistent presence of Stigmaria under coal seams that led Sir William Logan to formulate his theory of the origin of coal back in 1840.