Sydney Coalfield and the Princess Mine

Mines in Cape Breton towns like Donkin, Glace Bay and Sydney Mines all mined the same huge coalfield - named for Sydney - which extends from Cape Morien to Cape Dauphin, and 300 kilometres offshore. 98% of the Sydney Coalfield is underwater – it extends almost to the south coast of Newfoundland.

There have been about 100 mines in the Sydney Coalfield and it has produced more coal than all other Nova Scotia coalfields combined.

The Princess Colliery in Sydney Mines was the first to mine undersea coal in the Sydney Coalfield. Its main shaft was near the shore and the workings were entirely under the ocean.

The shaft was started in 1868 but due to issues with water leaks, the seam was not reached until 1876. The shaft had to be lined with metal through 300 feet of water-bearing rock to ensure safety.

Miners entered Princess in a cage that lowered them to the shaft bottom. Then they got into wagons (called a rake) and coasted thousands of feet down sloping tunnels to the working areas of the mine. In 1938, the cable that pulled the rake broke and 21 men died when it crashed.

The coal seam averaged 5'6" in thickness so miners could usually stand while working – narrower seams in many mines meant miners often had to work in very confined spaces, even lying down.

The coal was suitable for metallurgical purposes, being fairly low in sulphur and ash. (Thermal coal is burned to generate power and metallurgical coal is used in steel-making. Steel is mainly iron and carbon. The carbon is derived by heating metallurgical coal to around 1000-1100ºC in the absence of oxygen to drive off impurities until only the carbon remains.)

In 1955 the mine was connected to the surface by an inclined tunnel 3,445 feet long. This made it easier to get miners, equipment and coal in and out of the mine. For example, a 42" wide cable belt conveyor was installed to bring coal from the shaft bottom to surface - the first of its kind in North America.

Princess closed in 1975 after a century of work. It went as deep as 2000 feet under the ocean floor and extended almost 9 kilometres from shore.