The copper deposits at Middleton Tyas were some of the highest grade ore in Europe, although the amount was small. The first copper at Middleton Tyas was discovered in a quarry in c.1733. Trials in 1736 and 1738 were unsuccessful but profitable workings had been established by 1742 on land belonging to Lady d'Arcy. Further deposits were soon being exploited on neighbouring land by the Hartley family and by the Rev'd Tissington. Despite the close proximity of their different workings there was great rivalry between the owners, which is attested to in documents of the period.
The mines at Middleton Tyas suffered from extensive flooding and this was initially dealt with by using hand pumps. By 1752 the inadequacy of this method was apparent and by November of that year at least two pumping engines powered by horses were in use. These too proved unequal to the task and in 1753 two steam powered, coal fired, pumping engines were under construction. One of these built by the Rev'd Tissington was of the Newcomen type.
In 1755 there was a further advance in the pumping technique when ropes were replaced by slide rods. These were able to transmit motive power uphill over a distance of 200m. This more efficient pumping made it possible to reach the under-bed of the ore and consequently output increased.
By 1763 the recoverable ore at Middleton Tyas was virtually exhausted and mining appears to have ceased by 1779. The copper ore at Middleton Tyas was found in three major veins crossing through the area of the monument. Two of these extended north west, past the church, from Kirk Beck and the third lay square to these and extended north east to the east of Layberry Plantation. The mining activity was concentrated along the lines of these veins.
The areas of mining survive as circular mounds of earth, known as shaft mounds, surrounding a central hollow. These are formed by spoil from the excavation of shafts sunk into the ore bearing rock dumped around the shaft head. Some of the shafts were linked together by underground galleries, which followed the veins of ore and acted as drainage levels. The mounds are up to 8m in diameter and 2.3m in height. There are over 30 such shaft mounds within the area of the monument the majority being clustered into widely spaced groups located along the line of the veins. The largest group contains seven mounds and is located to the east of Layberry Plantation centred on NGR NZ23400580. Other groups of mounds are located at NGRs NZ23250576, NZ23450570 and NZ23350563.