Eventually, the biggest quarry in the area, Bryn Eglwys closed. Most of the people who had jobs in Abergynolwyn worked at that quarry. Many people were hurt by the closure. A man who lived in Abergynolwyn, named Henry Haydn Jones bought Bryn Eglwys. He also became a MP for the Liberal representing Merioneth. The quarry, which had closed, reopened in January 1911. Haydn Jones had no money to put into the quarry. But, when workers started mining in the quarry they pulled slate from the "Broad Vein" section. That section had slate that was very hard. It was not popular and most people did not want to buy it. They stopped getting slate from the Broad Vein and started getting slate from the "Narrow Vein," which had slate that was softer and that people wanted to buy. It was very expensive to build a new mind in the Narrow Vein. So, to save money, Haydn Jones made very small entrances into the mine, which were considered unsafe by many people. The sales of slate rose during World War I because people started building new buildings after they were destroyed in the war.