Reports from the mid 19th century indicated that the mine was not particularly rich. By 1885 three stoops were being worked yielding between 10 and 15 hundredweight per fathom. At this time the manager was John Trelease who had succeeded James Blenkiron and he was supervising extensive development works.

In 1885 a beam engine was purchased for the mine. It was delivered to Rowley Station in early July and was commissioned with some ceremony by Lt. Col. Monk of Durham a director of the owning company. It was given the name 'Whitwell'. Despite the optimism of this time the mine was nearing the end of its working life and closed in 1891.

Between 1860 and 1871 the mine is recorded as being worked by the Healey Field Co. from 1872 until 1873 by William Muschamp and from 1874 until 1891 by the Healey Field Mining Co. (The latter company being recorded in 1881 as William Whitwell, Lane and Blenkiron). The Healeyfield Mining Co. (Limited) was registered in July 1882 with directors named as: W. Whitwell, J. Blenkiron, H. Pritchard, J. Monk and E. Reid. The capital of the company was £30,000 in shares of £1.

The main adit level, mentioned earlier, was entered from near the farmhouse and was known as the 'Horse level' because in it ponies were used to pull the tubs containing ore. Dunham mentions two other adit levels, the 'Derwent Level', which emerges at [NZ 0656 4980] under a crag at the River Derwent and another, which was driven from near the farm at [NZ 0687 4870] for a distance of 800 ft. (244m) northwards.

It is likely that the Derwent level drains the whole of the mine above this level, the portion below being flooded; it is still open and has a stream emerging from it. While the mine was operating, the levels below the Derwent level had to be pumped out to prevent flooding and Wade claims to have seen pictures of large Cornish pump which was used for this purpose.

As well as the adit levels, there were a number of shafts each of which would have had levels driven from them (up to 10 old shafts are indicated in the area on both the 1923 and 1953 editions of the 1:10.560 scale OS map).

Dunham mentions the 'Gill shaft' at [NZ 0705 4763], the 'Spottiswood shaft' at [NZ 0693 4807], the 'Main or Whitwell shaft' at [NZ 0687 4863], two shafts south of Healeyfield Farm at [NZ 0695 4815] and a southernmost shaft near Charlton Howl at [NZ 0711 4702].

The Main or Whitwell shaft was sunk to a depth of 350 ft. (107 m) and had principal levels driven from it at the following heights above Ordnance Datum (AOD)

580 ft. (177 m) AOD – driven 920 ft. (280 m) south. 570 Ft. (174 m) AOD – driven 600 ft. (183 m) north. 485 ft. (148 m) AOD – the Derwent Level – driven 4,000 ft. (1.22 km) north to the river and 1,370 ft. (418 m) south. 320 ft. (98 m) AOD – driven 1,970 ft. (591 m) south and 250 ft. (76 m) north.

Above ground at the mine were several stone buildings, the only remaining of these being the old steam winding engine house. This is the square, two-story structure with arched openings where the ropes from the winding engine passed through to the headgear over the shaft. The building now contains straw bedding material and is obviously used as a byre. Its roof, have been tiled, is now covered with corrugated iron. The tallest building housed a beam-pumping engine. There was also a high, square chimney close to the engine house but this was demolished many years ago.

However, most of the buildings associated with the mine have gone and walking through the peaceful valley that is Dene Howl today, it is difficult to imagine that any type of industry ever existed in this isolated rural location