History of Roofing Slate
Slate has been quarried or mined throughout the United Kingdom, Europe, America and Asia for many centuries. The majority of the best grades of roofing slate were quarried in the United Kingdom and Europe, usually in mountainous terrain and often in hazardous working conditions. Due to the difficulties of transportation, slates were only used to roof houses close to the source of supply. With the advent of the Industrial Revolution (particularly in the United Kingdom) transport and technical innovation led to mass production and slates were sent throughout the country as well as to the wharves.
Many engineering advancements were made in the main slate producing areas. Machinery was being used to not only cut the slate, but also to haul it to the surface and transport it to rail.
In the United Kingdom, particularly Wales, these advances enabled slate to be transported to Bangor, a major trading port in the late 1800's and early 1900's. This was significant to Australia as many cargo ships would arrive from Australia laden with produce (eg. Wool, wheat) seeking a quick return voyage. Roofing slate was an ideal product for the return journey as it was available on the wharves and also provided ballast.
Fortunately the slate most commonly available was from Bethesda region, notably the Penrhyn quarry which is renowned for producing the worlds leading slate. As a result approximately 95% of all slate shipped to Australia (particularly the East Coast) around the 1840 - 1910 period was from this quarry. It is uniform in colour and often referred to as "Heather Blue" or "Purple Bangor".
As shipping from the U.K. changed from the West Coast to the East Coast the amount of slate shipped to Australia declined and significant imports did not resume until the early 1970's.