09. North Henblas Mine, Milwr

Introduction

This page describes a disused lead mine site that once occupied land to the west of the Glan-yr-Afon Inn at the hamlet of Dolphin, a mile south of Holywell. The field contains a single deep mine shaft originally described simply as ‘new engine shaft’, but which later became known as North Henblas Shaft. It was sunk to intersect lead ore deposits along the half kilometre long Pen-yr-Hwylfa vein, the eastern end of which terminates beneath the Glan-yr-Afon Inn. At its western end, the vein terminates near Pen-yr-Hwylfa Farm where the vein was worked by North Henblas Mining Company, so-called to differentiate it from the 1850s Henblas Mine, some 600 metres to the south.

The information here is the result of research by this writer that formed part of a study funded by Cadwyn Clwyd. I'm very grateful for their consent to reproduce it (somewhat amended) on this web-site.
 

Working within the constraints of the brief, documentary evidence specifically relating to North Henblas Mine was found to be sparce. The full story is therefore incomplete.

North Henblas Mine worked a lead ore deposit running approximately east-west, known as Pen-yr-Hwylfa vein. A detailed map of the area (FRO:D/GR/1705) shows no shafts or workings along the entire line of the Pen-yr-Hwylfa vein in 1825. In 1845 it became a requirement for all mines to furnish annual production figures. The earliest recorded production figures for North Henblas Mine however, date from 1862. At this time the mine was based around a shaft that now lies just on the western side of the A55 expressway (25” OS map 1869).

Ore was worked from a depth of about 240 feet below the surface at this location (Smith 1921). Several shafts were sunk along the line of the vein, all of which are likely to have been of similar depth.

“The belt of ground between the Caleb Bell cross-course and the Lower Coal Measures includes the richest part of the mineral tract of Halkyn Mountain” (Smith 1921, Pg 63). This large area on the eastern side of the mountain includes North Henblas Mine, Caeau Mine, Milwr Mine and many others. Despite the promising statement by Smith, this western part of North Henblas Mine only produced a total of about 1000 tons of lead ore and 4500 ounces of silver. The highest recorded output was in 1865 when around 200 tons of ore and 1000 ounces of silver were produced in the one year. This is a reasonable figure fairly typical of the mines around Holywell at the time, but small when compared with the annual figures of those such as Maeshafn Mine (1000-2000 tons) and Minera Mine (5000-6000 tons).

By the end of the 1870s the vein at this location appears to have been worked out, or become flooded.

The chief agent (overall manager) from 1866 until 1877 was William Francis of the famous and well respected mining family. After this time Francis left North Henblas Mine to follow his interest in other mines of the neighbourhood.

The above survey is produced with the permission of the British Geological Survey (Sept 2009). All rights Reserved. Based upon BGS Technical Report No: WA/88/2.

Please refer to BGS Terms and Conditions if reproduction is required: http://www.bgs.ac.uk/about/copyright/non_commercial_use.html

Another view down North Henblas Shaft                                                          Photo: Glen Walker
 

It's clear from the OS map above that no development had taken place on the site by 1869

By 1899 a milling complex had been erected on the site and then demolished after just seven years in operation. The disused engine house was then used as a Mission Room

Sinking North Henblas Shaft

It seems that work on sinking the shaft began in 1877. Compressed air for drilling was a new innovation at this time and was likely to have been used by the drillers in sinking the shaft. Although compressed air permitted significantly faster drilling than manual methods, water was not used to dampen down the resulting clouds of dust. Hence when drilling through cherts at the bottom section of the shaft, as already mentioned, miners will have significantly increased their chances of acquiring lung disease in the form of silicosis.

The method adopted probably involved a team of 4 or 5 men working in the shaft. Work would have included the frequent re-positioning of the pumps: raising (before blasting) and lowering (as the shaft became deeper); drilling shot-holes and setting charges. After drilling a ‘round’ of perhaps 20 shot-holes, each would be ‘charged’ (filled) with high explosives and a detonator. Wires from each of the detonators would be connected together and wired to an exploder on the surface. Drilling would re-commence after the poisonous fumes had cleared.

Water would have entered the shaft in the form of heavy rain, particularly as the shaft became deeper, and the team will have worn waterproofs whilst working. Some protection may have been provided by sheeting fixed above the top of the lowered shaft cage. On the surface, a steam engine initially operated a 14” lift pump to keep the shaft ‘dry’. Another steam-operated winding engine operated a cage in the shaft for lowering men. The cage may also have been used for raising wagons loaded with waste rock. A steam capstan winch was also used at North Henblas for installing heavy machinery and pump rods.

By 1879, the shaft had reached the depth of Roskell’s Day Level (330 feet below surface), and levels were being mined east and west along Pen-yr-Hwylfa vein. The pumping arrangement would have been altered at this depth to discharge all water into Roskell’s Day Level instead of raising it to surface; water in the Day Level running north by gravity and discharging into a brook south of Holywell. 

In October 1879, the shaft sinking team again continued sinking downwards at a cost to the company of £6 per yard depth. The team finished sinking in June 1881 at the final depth of 535 feet below surface and were mining to the east and west along the vein about 30 feet above shaft bottom.

It seems that mining at the deepest levels was severely troubled by water: The 14” lift pump struggled to cope and in November 1882 an additional 7” hose lift pump was installed. This proved ineffective and in May 1883 a larger engine was installed in the engine house and the following three months were spent installing an additional 24” lift pump.

By early 1884 mining was still hampered by water: Records suggest that a large Cornish engine was about to be installed. In February of that year, masons strengthened the engine-house wall and 23 men manoeuvered a huge cast-iron beam into place ready for the new engine. It appears however that the Cornish engine may never have been fitted as there is no mention of its installation in the cost-book and the mine closed down just four months later in June 1884. The mines’ sudden closure was probably due to a combination of high pumping costs and low production figures at a time of falling ore prices.

Production figures

The vein at North Henblas Shaft (east of the A55) was not very productive. Mineral statistics indicate that only about 200 tons of lead ore and 500 ounces of silver were produced in total (about a fifth of that produced at the west end of the vein, west of the A55).

Production figures for North Henblas Mining Co. Ltd. held by the Grosvenor family (upon which royalties were calculated at 20 shillings per ton) are even lower. This could suggest an unwillingness by the company to reveal actual output in order to reduce their costs. Conversely, it could also suggest a degree of leniency on the part of the Grosvenors in a difficult mining climate.

4     The Mill at North Henblas Shaft

Ore dressing

It appears the dressing floors may have been covered to protect workers from rain, as the 1893 sale catalogue (for Milwr Mine) mentions “galvanised shedding on pitchpine supports over dressing floors”.

A Blake's stone crusher, manufactured by R. Broadbent & Son Ltd. (copied from a 1930s Halkyn District United Mines catalogue) and typical of the crushers that may have been in use at North Henblas
 

The dressing process:

Cleaning

Cleaning of the ore/waste mix achieved by agitation in running water.

Jigging

After large lumps of pure galena were removed by hand, the mix would be placed into a jig. This is a simple wooden box (approx. 4ft long x 2ft x 2ft deep) shaken by a long rocking handle. By lifting the handle, the box is lowered into a water container. By ‘leaping’ (Ure 1867) up and down on the lever, the box is agitated or ‘jigged’ beneath the water, causing the heavier ore to sink to the bottom and the waste to rise to the top where it can be removed.

Crushing

The remaining material then needs to be finely crushed in order to separate ore from waste rock using buddles. In the days before crushing was carried out by machine, teams of workers achieved the same results using bucking hammers; tools having a thick steel plate about 4” x 4” with a handle about 2 feet long. 

Buddling

The crushed mix was then separated from waste rock in buddles. Although buddles of many different designs have been used at local mines, all buddles use a continuous flow of water to wash the mix down a slightly inclined plane, the lighter waste material being washed further than the ore, therefore becoming separated.