James Treweek became the new Mona mine Manager in 1811 and moved with his family to Mona lodge in Amlwch. He had a lot of experience of mining in Cornwall and brought Cornish men and methods with him.
He was in charge of the mine and transport to and from the port. He was also in charge of hiring and firing at the mine. This gave him great power and lead to complaints of nepotism. He was responsible for the setting of the price to be paid for each area of the mine to be worked. These “bargains” were publicly set every fortnight with a ” Dutch auction” method being used. The lowest bidder getting the work.
By 1828 Treweek was also in charge of the precipitation pits at the mine and his control was extended to the operation of the Parys Mine. A few years later he was in control of all aspects of smelting at the mine and at Amlwch port and was also responsible for all movement of shipping for the mine in the port area. He reported to Sanderson who was Lord Uxbridge’s estate manager.
One of his other duties was ensuring that sufficient coal and timber was brought into the port during the summer months to enable the mine to last over winter. In 1830 he advised Lord Anglesey on the application for a concession on the duty on candles and timber which was already given to the Cornish miners. He also secured a rebate on the coal duty for the transport of coal to Amlwch.
He was responsible for paying the smoke trespass to the Curate of Amlwch for the nuisance caused at the curate’s residence by the fumes from the smelting works. He also paid the ” English duty” to allow an English service to be held in the church each Sunday.
When Treweek came to Amlwch the smelters were only seen as a means of concentrating the ore. Treweek saw their potential in their own right. He paid particular attention to their development and even started to bring in ores from other parts of the country to smelt with the local ores. By 1820 the Mona mine had 16 smelter furnaces and the Parys works 9. The output of each group of smelters was around 350 tpa. As the production from Mona and Parys mines dropped additional material was brought in from other parts of Britain. The two master smelters at this time Rees and Morgan also reported to him.
Treweek’s influence in the Amlwch area went beyond the mine. He was the election agent for Plas Newydd. He arranged all the big occasions in the town and played host to the important visitors to the area. In 1831 he arranged a dinner for 1400 people on the mountain to celebrate the Coronation.
Treweek held control of all these aspects of mine operation until his death in 1851.
His family then took control and were also influential in the Amlwch ship building industry which developed in the middle of the 19th Century.