Copper was rediscovered at Parys Mountain between 1761 and 1768 on the estate of Sir Nicholas Bayly (1707-1782) of Plas Newydd, who owned Cerrig-y-bleiddia Farm, on the east of the hill and also had a share in Parys Farm on the western part. A legal dispute between Sir Nicholas Bayly and the other owners of Parys Farm resulted in the engagement of solicitor Thomas Williams (1737-1802) of Llanidan. In 1778 Sir Nicholas Bayly leased his share in the Parys Mine to a Macclesfield company in which Thomas Williams was partner. By 1785, the lease had run out and Sir Nicholas' son and heir, Henry Bayly, Earl of Uxbridge (1744-1812) went into partnership with Thomas Williams to form the Mona Mine Company. Production began to decline around 1850 although it continued until 1883 and ore recovery carried on into the twentieth century on a small scale.
From the guide to the Mona Mine Papers, 1787-1865, (Bangor University)
