The lovely beach at Aberbach gives some clues. There’s slate nearby and the tiny quarries in the Dinas area were probably the earliest attempts to work slate in the region; George Owen, writing in the very early 1600s referred to sites near Newport which produced ’tiling stones’. The enterprise depended on transport by ship and the stone was loaded in the little ports of Cwm-yr-Eglwys and Newport to be sold around the country. As late as the mid-nineteenth century companies were being formed, money raised on the stock market and fortunes lost.
The problem was that, in spite of the marketing which compared our slate favourably to the north Wales stone which roofed the world in the 18th and 19th centuries, the local blue slate often lost colour and flaked; with its high pyrite content it degraded quickly, causing roof timbers to rot and lichen to grow. Local people used it on their roofs but protected it with a layer of mortar.
There are still some signs in the cliff face of older slate workings, but the ‘Hescwm Slate and Slab’ company, formed with £30,000 in 1878 was dissolved in 1887, probably without any quarrying having been done. Later attempts to revive the company in the 1930s failed and it was noted anecdotally, “The slates were so poor the company went out of business”.
For more information see “The Slate Quarries of Pembrokeshire’ by Alun John Richards, published by Gwasg Carreg Gwalch, 1998.