Eglwys quarry near Abergynolwyn and the Talyllyn Railway that served it. There was some improvement during the late 1930s, with 140 workers employed in 1940, but the Second World War brought further drops in production, with the number of men fell to 40 in 1944. After the war, the industry continued a slow decline, with industrial action closing the quarry for part of 1947. During the 1950s only about 40 men were working, all in Foel Grochan quarry. In 1956, brothers Gwilym and Dewi Lloyd took over the quarry under the name Wincilate Ltd. Rapid modernization and mechanisation of the quarry allowed it to continue to produce slate into the 1990s. Aberllefenni was the last working slate mine south of Blaenau Ffestiniog. However, by 2002 it was no longer economical to extract slate at Aberllefenni and the mine closed in 2003. The slate mill continues to operate, processing slate imported from Blaenau Ffestiniog, Penrhyn and China. Small pieces of Aberllefenni slate are still available for name plates. Operations One of the reasons for Aberllefenni's continued use was the high quality of the slate extracted. There are two major veins of slate running parallel to each other through this region of mid-Wales, the Broad Vein and the Narrow Vein, the latter of which Aberllefenni extracted. The broad vein is of considerably poorer quality than the narrow vein, and the slate it produces is of little use in roofing slates or polished surfaces. Instead it was used in walls, fences and hardcore. The narrow vein was of much better quality and could be used in much higher quality applications and fetched higher prices. Slate extracted from the narrow vein at Aberllefenni is deep blue and extremely hard and dense. It resists fine splitting, so most of the mines' product was large cut slabs rather than split roofing slates. Foel Grochan mine consists of eight near-horizontal tunnels at approximately vertical separation. These were bored into the valley side just to the north of the near-vertical narrow vein. Each tunnel connected to a large chamber from which the rock was extracted. These chambers ranged from in length with of rock left between the bottom of one chamber and the top of the next lower chamber. As more slate was extracted, several of the upper chambers were joined vertically to form an extremely large cavern known as Twll Golau which is open at the top.