The fells and dales of West Durham bear many scars of the extensive mining operations, thought to have been carried on from the time of the Brigantes (the tribe occupying the area in pre-Roman times) for the extraction of lead, silver and iron ores and other minerals. By contrast the Consett area, in the north west of the county, is more usually connected with coal mining and especially with steel production.

There was, however, a mine at Castleside, which worked the Healyfield lead ore vein, which is located at the easterly edge of the northern Pennine ore field. The ore vein runs roughly north – south and occurs within a major fault zone, which at the surface brings Lower Coal Measures strata on the east against Millstone Grit on the west along much of its course between Wheatley Grange, 3.5 miles (5.6 km) north of Wolsingham and Greymare Hill, 2 miles (3.2 km) south west of Whittonstall. It is thought that the primary mineralisation in the area took place towards the end of the Carboniferous and beginning of the Permian geological period around 280 million years ago.

It has been suggested that the history of this mine stretches back some 800 years (Wade asserts that it operated in the reign of Edward I, 1272 – 1307) but whether or not this is the case it was certainly working from very early times. Whellan's Directory (1894) states that lead mining at Healeyfield is of very ancient origin and that the mine there is considered the oldest in the county. It is known to have been in the ownership of the Dean & Chapter of Durham and at one time supplied silver to the Durham mint.

The mine was situated half a mile (0,8 km) west of Castleside crossroads at Dene Howl National Grid Ref. [NZ068486] from where the main adit level (an adit is an almost horizontal entrance to a mine for access or drainage) at 655 ft. (200 m) above ordnance datum (AOD) extends 4,500 ft. (1.37 km.) in a southerly direction. It was primarily a lead mine and although no pre-1856 returns are available, production for the last period of its activity (1853 – 1891) amounted to 10,490 tons of lead concentrates. However, in the 36 years following 1853, it also produced 108,336 oz of silver.

The concentration of silver in the Healeyfield vein is comparatively high, being given by Dunham as 15oz. per ton of lead and Wellan's Directory as 18.5oz.per ton. Although concentrations can be as high as around 40oz. per ton in the Aston Moor area, this is exceptional, a value below 10oz. per ton being more usual over the ore field as a whole. It can therefore be seen that the Healeyfield mine used to tap a valuable mineral resource.

Healeyfield belongs to the Muggleswick group of mines and in the twelfth century Muggleswick was granted to the Prebendaries of the Dean and Chapter of Durham Cathedral.

In 1545 The Dean and Chapter leased mines in the Muggleswick area to the Duke of Suffolk and in 1624 James I granted George Duke of Buckingham, all Mines Royal within 10 Miles of Muggleswick.

In 1741 the London Lead Co. acquired the Muggleswick mines and it was their agent, a Mr Shirley, who built the Farmhouse at Dean Howl around the beginning of the 19th century.