Henry Simpson's Black Diamond Line began operating as a coal importer in 1854. In 1882 he acquired his first steamship the Birksgate, which had some cabin accommodation and carried passengers in addition to its coal importations.

So successful was this side of his business that Simpson ordered another steamship for the Black Diamond Line; Tenterden arrived in July 1883. Her passenger accommodation was increased later that year.

Henry Simpson was the right man in the right place and was able to take advantage swiftly of the demand for coal by the Wallaroo copper smelters. Trade with the Newcastle coalfields had been opened up following the breaking of the Australian Agricultural Company's monopoly in the early 1850s. Simpson used his own ships and chartered others to fill the need. Later he would charter a steam ship in an emergency situation and was impressed by their capacity to run to a schedule. He bought one of his own and later added the Birksgate.

After Henry Simpson's death in 1884, the business was continued by his son. The success of the Black Diamond Line mirrored the growth and decline of the copper mines and smelters at Wallaroo. When these began to decline so did the Black Diamond Line. Its cargo and passenger business was purchased by the Australasian Steam Navigation Company in the late 1880s and by 1895 the Black Diamond Line had ceased operation.