Mui Wo Silver Mine – Part Two The Mine

Tymon Mellor: On the 28^th March, 1886, the first of many blasts was initiated at the Mui Wo silver mine. The owner, Mr Ho A Mei (see Part One of this article linked below) wanted to extract the galena ore to aid in the mineral processing of the richer ore from a Mainland mine of his. The mineral processing facility was also located at Mui Wo because of the availability of ample water and security of the location. Part Two of this article describes the development and operation of the mine along with the mineral processing facility.

The Mui Wo Mine

This part of the article describes the abandoned underground workings of the Mui Wo silver mine. The shafts, tunnels and adits have been not be maintained in over 100 years and their condition is unknown. These workings should not be entered as they are flooded and unsafe, except for bats to which they are a haven.

The mine is located in the low foot hills to the north of Mui Wo. Its location was described in The Hong Telegraph of September, 1905 as “The mine, which is on the face of a hill not quite a mile from the sea, is approached through a beautiful valley running away from a sandy shore now transformed into a western seaside resort for visitors and pleasure seeking picnic parties”.

At the time of the mines operation, Lantau was part of China and administered from Canton (‘Guangzhou’). The residents were mostly farmers and fisherman, leading a rural life. There was no ferry service, no electricity and no form of modern communications, making the island remote and isolated to all the changes in the region.

The Geology

The geology of the Mui Wo area is predominantly Lantau Granite, but at the location of the mine there is an East- West striking fault, set at around 70 degrees to the vertical separating a magma intrusion of Porphyritic Granite (Rhyolite) dyke to the north. Mineralisation had occurred in the hydrothermal veins in the rocks associated with the fault, with galena being the dominant metallic mineral. Both lead and silver, along with other mined minerals were contained within the galena which were to be found within a series of parallel faults. The change in geology resulted in the formation of the adjacent waterfall, Silvermine Waterfall, that now is an attraction to walkers and visitors alike.

Mine History

There are no formal records for the mine, but contemporary reports are still available from newspaper articles and other reports.

The mineral vein was probably first discovered in around 1619, as reported by Chu and Chan . They note that the village near the mine, Pak Ngan Heung or “White Silver Village” is clearly named after the mining activities. The village has a Man Mo Temple that can be traced back to the Ming Dynasty (1573 to 1620). Legend has it that the Man Mo Temple was built to resolve an issue regarding the silver mine.

It is likely that the mineral vein of galena was first identified at the top of the waterfall, where the mineral vein crosses the river. Intermittent surface mining would have taken place, but without processing facilities, selling the raw ore would generate little income. However, it did raise the fact that the galena was present.

Following the intervention of Mr Ho and Mr Candler, the mineral was exploited for commercial purposes. On the 28^th March, 1886, a Sunday, the Tai Yu Shan silver-mine was formally opened, as reported in the local press “in the presence of about thirty European residents of Hongkong and large number of Chinese”. Mr Chandler with the assistance of Mr Philips, a Cornish miner, had drilled fourteen holes and charged them with explosives. The subsequent explosion dislodged a ton of earth, throwing smaller pieces, two to three hundred metres from the blast. The force of the explosion exposed the mineral vein and the guest collected samples of the ore before retiring back to the shore and the boat back to Hong Kong for toasts and tiffin.

Development of the mine was planned to take six months but with difficult working conditions and unskilled labour, it was 12 months before production would commence. During that time there was sickness amongst the European workers and local labourers on occasion refused to attend work. However, a greater problem seemed to be the lack of knowledge and interference from the Canton authorities. To ensure the mineral royalty of 10% was paid and to look after the interests of the Government a “mandarin” was appointed to the mining venture. Mr Chandler spoke of his frustration dealing with this man who was, “totally ignorant of everything connected with mining” and “men should not be harassed in carrying out their duties by the supervision of a man who knows nothing about the matter”. He encouraged the Viceroy to appoint a capable team to look after the mining and mineral interests of the district.

At the opening of the ore processing facility in April, 1888, Mr Ho presented the company accounts, from November 1883 to February 1888:

In a February 1888 article, the mineral ore is described as; “carrying 150ozs of silver to the ton”. Modern mines yield 8-13 ounces per ton suggesting the 150 may be a typographical error and the true value was probably ‘15’. On this basis, over the ten years during which the Lantau and Tamchow  mines were operating, I would estimate around 60T of silver was produced and 50,000m³ of spoil.

Mine Operation

Although there are no specific details available about the mine operation, we can piece together the key details from the existing structures which remain today.

The mine operated in a time before electricity was generally available and the contemporary reports indicate that the mine winches and water pumps were powered hydraulically using the water pressure from a dam, 100m above the mine. The processing plant was located at the coast and had a number of steam engines to provide the power to operate the machinery. Linking the two sites was a wire tramway carrying the ore from the mine to the processing plant.

A map of the mine was developed by Mr Rocky C H Tan and published in the Geological Society of Hong Kong newsletter, and this has been further refined following recent investigations (https://photomarket.hk/thread-6517-1-1.html).

The original mine development was at the upper tunnel at the main Portal A. The portal is located on the hillside and was the initial location of the mineral find. The adit at this level would allow the miners to extract the mineral with the minimum of development and provides natural drainage. The portal is now blocked with a wall and has been developed as a local attraction.

At portal A, the Government has developed an attractive feature for visitors and within the paved area the mine operational dates are identified as 1862 to 1896 and the notice board advises, “Silver mining began in about 1910..”; indicating a poor understanding of Chinese industrial history and consistency!

Working to the west, shaft number 3 is within the mine connecting the upper and lower parts of the mine. The shaft used to be accessible to the public, allowing people to throw rocks and other objects into the void. With the construction of the wall it is no longer accessible.

Within the tunnels are a number of flooded shafts, linking to the lower workings.

Shaft number 4 further to the west is located on a hillside and would have been constructed to provide natural ventilation of the mine and to allow blast gasses to be exhausted.

A fifth shaft was identified on the plan developed by Mr Rocky C H Tan, but recent investigations suggest the shaft is not associated with the known mine workings.

Unlike the other shafts that are round, shaft 5 is square around 2.5m by 4m. The locals refer to this as the Japanese shaft, suggesting it was constructed by the Japanese in the Second World War as there was a great demand for lead, not only for bullets but also for vehicle batteries. The Japanese mostly likely sunk the shaft to locate the mine vein. The shaft was filled in by the villagers around 20-30 years ago to prevent illegal access, the concern being that if people got into the mine they would never be located.

Excavation of Portal B, close to the river, commenced shortly after the upper adit and by March 1888 a shaft up to 24m deep had been sunk along with 640m of tunnel. The portal had been cut into the hillside and provides access to three tunnels portals and all tunnel levels. This would have been the centre of the mine operation. Material from the upper drive could be dropped down the internal shaft then removed along with material from the lower drive in muck cars through this opening. At the back of the portal there seems to be a flooded shaft to the lower level, and this would be the shaft for removing the excavated ore and containing the pipe work required for the hydraulic water pump.

In the centre of the portal is a structural brick wall, and smaller brick piers are visible as you enter the cutting. The wall could be associated with the rope haul facility, supporting the balance weight of the end wheel, but it is more likely to be a support for the winching systems to the lower levels. Contemporary reports note “a hydraulic system is about to be erected for working a set of 7-inch pumps and for hauling purposes”.

There is a short tunnel perpendicular to the other tunnels. This could be exploratory looking for parallel veins but is more likely to relate to the portal operation. It could lead to the top of a shaft (now flooded) or it could have been used as a back shunt to be used by the hand pushed mine cars. The lifting equipment could automatically tip ore into the cars for removal to a stockpile and loading onto the rope haul facility and transportation to the processing facility.

Shaft 2 is located to the east of the waterfall, and was probably provided for ventilation and clearance of blast fumes.

Portal C is located close to the east end of the mine, and the provision of this access portal was probably related to relieving the logistical constraints at Portal B where all the excavated material would be removed. It may also have been associated with water control, providing a second discharge location. The entrance may also be related to future development of the mine, providing secondary access and egress in the event of blasting.

Mine shaft 1 is located at the east end of the mine, and is located just below the hillside grave yard. The shaft is very shallow with only a nominal rock cover and is now home to a colony of bats who live on the underside of the cover. The shaft would have been primarily for ventilation.

The flooded level of the mine was developed from around 1880, with development works 24m below the lower adit. Connection to the flooded level was achieved with a series of now flooded shafts, and the lifting equipment and pump in portal B.

Water Management

From his experience in Australia, Mr Ho knew that the quality of ore improved with depth, thus the excavation proceeded below the water table once suitable pumps were installed in early 1888. The mine utilised a hydraulic motor, driven from a 12 inch (300mm) water main, supplied from a dedicated reservoir some 100m higher up the hills. The reservoir is still in place, overgrown, silted up and abandoned, and even the cast iron main has been removed.

Contemporary reports describe, “This motor has only recently been patented, but we understand it is a great success, and will carry out the winding and pumping of this mine to a great depth”. By the 1880’s electricity was just starting to be adopted by the mining industry where the steam engine still was the main source of power. For shallow excavations where the depth is less than 10m deep, it is possible to install a pump at the surface and suck the water out with a hose. For deeper excavations and mines, this approach does not work due to the effect of cavitation, where-by air bubbles form in the water stopping the pumping actions.

The beam engine was developed for the Cornish mining industry, utilising steam and later steam engines to drive a vertically mounted piston rod, just like the ‘nodding donkeys’ seen in modern oil fields. The piston rod is extended down the mine and used to drive a pump in a sump at the lowest point in the workings. In the case of the Mui Wo mine, rather than using a rod to provide the power, the pump design used pressurised water, i.e. hydraulic power. This utilised the 100m head of water available from the higher dam, to provide 10 bar of pressure to drive the pump.

At the time the mine was commissioned, a number of new hydraulic pumping systems were being commissioned. In the UK at the Sir Francis Mine, a lead mine in north Yorkshire, introduced a combined pumping and winding engine supplied by ‘Hathorn, Davey and Co’ and which was commissioned in 1881. This would match the description given for the Mui Wo mine. However, in the United States an engineer called J Moore patented in November, 1886 a new arrangement for the control systems for a hydraulic pump that became popular in a number of mines.

Wire Tramway

The contemporary reports all describe a 3,000ft or 914m “Wire Tramway” or aerial ropeway, to transport the ore from the mine to the processing facility. We would recognise this as a cable car for ore which was popular during the period as it was simple and cheap to erect, requiring only limited ground access for the towers and a single steam engine to drive it. The system could use locally sourced timber or steel for the towers, with only the cable and wheels needing to be imported. There are a number of examples in Hong Kong of these systems including a man riding version used during the construction of the Beacon Hill railway tunnel.

The loading station was likely to be located close to Portal B, and here, ore from all the drives could be delivered to the ropeway or stockpiled in the event the system was not operating. The discharge station would have been close to the processing facility, either directly loading in to a hopper to feed the crusher, or feeding a stock pile in the event the crusher was not operating.

Processing Plant

On the 15^th May, 1888 the mineral processing plant was formally commissioned in front of a large group, described at the time as “500 foreigners and as many Chinese”. This was the most modern plant in China and represented a significant investment in the mine. The plant provided two key functions, dressing the ore followed by smelting and the production of silver. The facility was assembled by a Mr C S Turner, who had experience in smelting operations in both England and Russia and was assisted by a Mr Sinclair. The building and equipment was supplied by ‘Robey & Co’ of Lincoln, England.

The processing plant was a steel structure 73m long, with two levels; the upper containing the dressing equipment, crusher, rollers etc and the lower half was the processing and smelting equipment. The whole facility was driven by a fifty horse power stream engine and a thirty horse power steam boiler and designed to process 40 tonnes of ore a day.

There are no known photographs of the plant, but there are pictures of similar plants from the same period.

As recorded at the opening of the plant, the list of key equipment included:

“In this house is a fifty-horse power engine and boiler, a stone breaker, three pairs of crushing rolls, eight jiggers and two buddles, all driven by the engine first mentioned. In the lower part of the works are situated a thirty-horse power boiler engine, driving four frue vanners, a six-horse power engine working a lift to the top of the mill, and also wirerope tramway to the mines, and another six-horse power engine for driving the blasts of the furnaces.”

A report from February 1888 further describes “The smelting works will for the present consist of four Scotch hearths, two calcining furnaces of the reverberatory type, a reverberatory smelting furnace and an English cupelling furnace “. Along with the furnaces, the building also included a full laboratory to analyse the ore and smelted minerals.

Mineral Processing

By the end of the nineteenth century there were four methods used to extract silver from ore, depending on the form of the silver and the availability of resources. These processes were an amalgamation process requiring the use of mercury, a wet process, smelting with lead ores and smelting with copper ores.

Based on the comments by Mr Chandler, it is clear the process adopted at the works was to smelt the Mainland silver ore from Tamchow (see Part 1) with the galena from the Mui Wo facility to extract the silver.

The ore would have been taken into the upper portion of the facility where is was crushed using a rock breaker, most likely the popular Blakes stone-breaker. From the breaker, the crushed ore passed through three sets of rollers reducing the rock to fragments about 1.5mm in size. This ‘sand’ then passes through jiggers where moving water is used to separate the materials by density, the heavier particles containing the best ore. The overflow water from the jiggers also contains fine particles of lead and silver and this was washed again with a buddle embedded in the floor. The fine concentrates would be added to the centre of the buddle and a rotating arm would use gravity to separate the high grade from low grade material, with the light low grade ore travels furthest from the spindle. Once full, the bundle would have been cleaned out with the good material, taken to the furnace, and the low grade material disposed to a spoil heap.

The good ore collected at the jigger would then have passed over a Frue vanner, a vibrating moving belt with water washing away the lighter material and the ore deposited in a collection box at the end. The resultant ore would then be taken to the furnace house for smelting.

The crushed ore would have been heated to a temperature of 1,450°C to 2,000°C within a calcining reverberatory furnace, fired by coal with a steam powered blower. This furnace provided sufficient heat to melt the silicates and sufficient carbon to reduce the oxides. The galena mined at Mui Wo would then have been added to provide a flux and to promote melting of the silver mineral.

During the fusion process, the lead and precious metals sink to the bottom, and the less dense slags floats to the top. The slag would then have been drained off and the remaining heavy material, an argentiferous lead being tapped off and poured into moulds in preparation of the next step in the refining process.

Using an English cupelling furnace, where the cupel is made from a cement material held within an iron frame, the ore is heated again but isolated from all sources of carbon. With the heat blasting over the surface of the metal it would have become iridescent (rainbow tint) as the last oxides are burnt off, the silver can then be run off from the top of the lead.

The fumes from these processes were highly corrosive, consisting of lead oxide, sulphide and sulphates as a fine dust and some sliver. To avoid the noxious vapours, the flue needed to be long in order to discharge the arisings remote from the facility. In the case of Mui Wo, there was a condenser to cool the gases leading to an 18m tall chimney located 30m up the adjacent hill side.

Plant Location

The location of the processing plant has been the subject of much speculation. The contemporary reports identify it on the coast and linked to the mine with a 914m ropeway. In Andrew Wood’s article, he suggests the site of the current Outdoor Recreation Camp as being a possible site. This however is beyond the 914m radius and more importantly there is no sign of any remains of spoil material.

Two other areas could be the possible site for the plant location. The village shown on the old maps as Mang Tong, now the Mui Wo Hotel site, or close to the site of the current Mui Wo Sports Centre. Again, looking at the old maps and 1963 aerial photograph there is no sign of any spoil material at Mang Tong, but the Mui Wo site has a large area of land extending un-naturally into the sea. A quick measurement indicates the areas of land to be around nearly 20,000m², assuming an average depth of 2m, this would give a volume of 40,000m³ or close to the 50,000m³ of spoil generated by the mine.

The adjacent hillside would have made an ideal location for the chimney, and the whole site would have been visible from the bay. The suggested location is shown on the plan below.

There is no sign of any evidence to support this theory as there is nothing visible at the site. There is an old tower on the hill, but this is stone with a design consistent of a lookout. The 1963 aerial photo does indicate a large building in the general area of the suggested facility, and these modern structures may have been erected on the foundations of the former facility. It is unlikely that the foundations were dug-up and the land reinstated to farm land.

Closure

When the mine closed is not recorded, but there seems to be contemporary agreement that it was sometime in 1896. Why the mine closed is also open to debate.

With the ceding of the New Territories to the British in 1898, Lantau Island became part of Hong Kong. A survey of the new lands was carried out by Mr Stewart Lockhart and reported in October, 1898. The section on the Geology of the New Territories by Mr Ormsby, the Director of Public Works, reported, “Silver and lead were worked on the south of the island of Lantao within recent years, but without success financially, possible due rather to Chinese official interference and bad management than to the absence of a paying richness in the ore. Expensive buildings were erected on the sea-shore, and machinery said to have cost 100,000 dollars imported and erected. Even when the speculation collapsed, the plant was valued at $30,000, all of which is said to have been abandoned. Only the foundations and cement floors of some of the buildings remain, and the brick chimney shaft of the smelting works.”.

In a report in September, 1905 a former mining engineer for the mine noted “there is a large quantity of ore to be found”. The same report noted that a group of “influential business gentlemen in Hongkong” were contemplating re-opening the mine. Clearly it was thought that the mine still had value.

Closure of the mine was probably the result of a number of reasons. Firstly, the value of silver had been in steady decline, and reached an all-time low in 1896. Secondly, the owner was also having to make additional payments, in addition to the 10% royalty, as there were feng shui costs and labour issues along with the salary of a “mandarin” appointed by the Government to look after the interests in the mining venture. As recorded in 1888, “this official seems to imagine his principle duty is to interfere and squeeze the mine owners under threat of placing all manner of obstacles in their way”. It is therefore likely that the intention was to temporarily suspend the mining operation, hence the plant and equipment being left in place waiting for the price of silver to rise, but also to put pressure on the Canton authorities to re-negotiate the royalty. Neither happened, and the mine was abandoned, equipment removed and all traces of the processing plant lost or as reported in 1905, “The soft hand of nature now has laid her cloak of green around the remains, the walls have long since crumbled away, and only the cement floor is observed near the beach where it serves the peasants, from the dwelling close by, as a drying ground for rice and fish.”.

The mine and processing facility were originally developed as a template and showcase for private enterprise and the application of modern mining technology within southern China. There was brief window of interest within China, but it closed and it would be another 100 years before private enterprise was welcome once more.

This article was first posted on 19th June 2017.

Sources:

1. The China Mail, 28 March 1886
2. The Hongkong Daily Press, 2^nd February 1888
3. The China Mail, 16^th April, 1888
4. The Hongkong Daily Press, Mail Supplement, 19^th April, 1888
5. The London and China Telegrpah, 22^nd May, 1888
6. The Chinese Recorder May, 1888
7. The Hongkong Telegraph, 30^th September, 1905
8. http://www.lowtechmagazine.com/2011/01/aerial-ropeways-automatic-cargo-transport.html
9. Hong Kong Mining History, Jackie CT Chu and Jacky SL Chan 2015
10. http://vintagemachinery.org/mfgindex/detail.aspx?id=2659&tab=6
11. The Wire Rope and Its Applications, W E Wipkins, 1896, https://archive.org/details/wireropeanditsa00hipkgoog
12. Water Engines, http://www.douglas-self.com/MUSEUM/POWER/waterengine/waterengine5.htm
13. Mining, An Elementary Treatise on the getting of Minerals, by Arnold Lupton, 1893
14. Metallurgy, E.L. Rhead, 1895
15. The Metallurgy of Lead and Silver by Henry F Collins, 1899
16. Machinery for Metalliferous Mines by E Henry Davis, 1902
17. British Progress in Pumps and Pumping Engines, Volume 2, 1905
18. Geological Society of Hong Kong Newsletter Volume 21 No 1 Exploration on the Existing Silvermine Cave and Study for its Re-Opening, August 2015 by Mt Rocky C H Tan
19. Hainan Island: A Brief Historical Sketch by D L Michalk
20. Historic Maps www.hkmaps.hk
21. Images https://www.eggstudio.com/
22. Mine details https://photomarket.hk/thread-6517-1-1.html

Related Indhhk articles:

1. Mui Wo Silver Mine – Part One – The Owner
2. Mui Wo Silver Mine – 1905 newspaper article
3. The Silver Mine of Silver Mine Bay
4. Robey & Company, Lincoln, UK – suppliers of structure and machinery at Silver Mine, Mui Wo