Metal and stone, culture and technology: how Cornwall's industrial past has shaped the modern landscape.

 


Lode and Shode

 

Introduction

Mount Hermon, St Just. Slot-like cuttings in the cliff face where tin ore has been extracted. Although the date of these workings is unknown they are potentially the earliest excavations of tin in the county. Photo © Cornwall County Council Historic Environment Service Mount Hermon, St Just. Slot-like cuttings in the cliff face where tin ore has been extracted. Although the date of these workings is unknown they are potentially the earliest excavations of tin in the county. Photo © Cornwall County Council Historic Environment Service

Before 1700 the tin industry in Cornwall was of international importance whilst copper was of little commercial interest. A substantial amount of the tin produced in this period came from tin streaming. In some places however, streamworking was not feasible and the tin ore had to be dug from dry ground.

 

In some cliff-side locations veins of tin (known as tin lodes) were exposed and these were quarried out, leaving tell-tale linear cuttings in the cliff face. It is likely that these cuttings, or ‘open-works’ are amongst the earliest attempts at tin mining in the county.

 

Open-works were also used to quarry tin from inland lodes. But a much more widespread feature of the early mining industry are lode-back pits. These are lines of shallow shafts strung out along lodes. They are interconnected by underground tunnels and alongside some are the remains of platforms for the machinery used for lifting spoil and ore out of the pits.

 

Lode-back pits and open-works represent the beginning of the move underground which led to the more familiar deep tin and copper mines based on shafts and engine houses.

 

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Shode workings

A substantial amount of the tin produced before 1700 came from tin streaming. Some works exploited material known as ‘shode’; tin-rich stones lying on the ground surface after being eroded from an exposed outcrop. Streamworking techniques involved washing the shode to remove unwanted material and retain the tin ore (cassiterite). The process required large quantities of water to be brought to site and could only be carried out on sloping ground.

 

Shode works at Belowda Beacon, Roche. Shode pits in the foreground and in the distance appear to be randomly dug; those in the main area of the photo are following the line of lodes. The larger pits and the linear trench in the foreground are later lode-back workings and shafts. Photo  ©Cornwall County Council Historic Environment Service Shode works at Belowda Beacon, Roche.  The larger pits and the linear trench in the foreground are later lode-back workings and shafts.  Photo © Cornwall County Council Historic Environment Service

 

At some locations deposits of shode were located on hill tops or on level plateaux, where streamworking was not practical. Here the areas of shode were dug over by pick and shovel, leaving a pock-marked landscape made up of hundreds of small pits and spoil dumps. The hillocks left by the tinners were known as shambles. Material excavated from the shode pits was taken downhill to a water source for cleaning and processing.

 

At some sites the shode pits are clearly following the lines of lodes, but at others there is no obvious pattern to the workings. This suggests either that a spread of material in the ground adjacent to the lode has been worked or that the shode ground has been dug over again and again.

 

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Open-Works

The tinners gradually turned their attention away from the increasingly exhausted alluvial tin streams and surface deposits of shode and towards the lodes (mineral veins) themselves. Open-works are one type of early lode working site, sometimes called ‘beams’ or ‘coffens’. They represent opencast quarrying of the lode, which produced narrow elongated cuttings.

 

Many open-works were cut into hillsides so the ore could easily be removed as the work proceeded, through the area already mined. Open-works which were sunk vertically down into a lode formed large pits with sheer sides, presenting the problem of how to lift the ore out of the working. The solution was to cut the trench in stages, producing a stepped profile. Each step was roughly six feet below the next – as high as a man could throw up the tin ore with a shovel.

 

The largest open-work in Cornwall is at Mulberry Hill. Here there were several parallel, closely-set lodes of tin and so the ground was taken out in bulk This pit was still being worked in the nineteenth century but initial excavations at the site may have been much earlier. The tin ore at Mulberry pit was sufficiently weathered to allow its removal by pick. Records show that five to six tons of ore was the average weight of ore mined per person in one day. Photo © Cornwall County Council Historic Environment Service Mulberry Hill, Roche.  Photo © Cornwall County Council Historic Environment Service

In some open-works the ore was heavily weathered and could be excavated with just pick and shovel. Where the rock was harder, hammers and wedges were used to break it up. Reservoirs found at some open-works suggest that the technique of fire setting may have been used to fracture the rock by heating it with a fire which was then doused with water from the reservoir.

 

The largest open-work in Cornwall is at Mulberry Hill. Here there were several parallel, closely-set lodes of tin and so the ground was taken out in bulk This pit was still being worked in the nineteenth century but initial excavations at the site may have been much earlier. The tin ore at Mulberry pit was sufficiently weathered to allow its removal by pick. Records show that five to six tons of ore was the average weight of ore mined per person in one day.

 

Historic documents show that open-works were mainly in use between 1500 and 1700 but it is likely that the first open-works are earlier, when the documents are less clear about the specific type of operations carried out at tin works. It is also more than likely that cliff face sites such as Mount Hermon were being quarried at a very early date.

 

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Lode-Back Workings

The earliest underground mines in Cornwall were worked by pits or shallow shafts, often interconnected by tunnels and galleries underground, and usually dug in lines following the mineral veins or lodes. Lode-back pits or shafts, as they are known, were in use by the thirteenth or fourteenth centuries.

 

Craddock Moor, Minions. Three lines of lode-back workings follow the mineral veins (lodes) across the moor. Each pit is surrounded by a mound of spoil. The pits are typically five metres deep and are connected underground by tunnels and galleries. Photo © Cornwall County Council Historic Environment Service Craddock Moor, Minions. Three lines of lode-back workings follow the mineral veins (lodes) across the moor. Each pit is surrounded by a mound of spoil. Photo © Cornwall County Council Historic Environment Service

Lode-back workings removed tin ore that lay above the water table and the pits are usually several metres deep. The principal involved – sinking shafts into the tin ground and mining the ore by the use of galleries along the lodes - was the same as later shaft mining. Mining to a greater depth presented problems with drainage. The move from lode-back working to shaft mining began when the easy pickings near the surface became exhausted and technological advances made deep working feasible.

 

Unlike later deep mining, where very few shafts were used to extract the lode, shallow working required numerous pits. This is because the underground excavations were very narrow and it was easier to sink more shafts than to haul waste long distances back to the original shaft to take it to the surface.

 

Although later deep mining often destroyed all trace of earlier lode-back working, at mines where the lodes were not sufficiently rich to warrant deep working lode-back pits have survived and are a familiar feature at many mining sites.

 

Lode-back pits at Carn Brea. Photo © Cornwall County Council Historic Environment Service Lode-back pits at Carn Brea. Photo © Cornwall County Council Historic Environment Service

 

 

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Removing and processing the ore

A windlass shown in operation in Eastern Europe from a 1556 engraving by Agricola A windlass shown in operation in Eastern Europe from a 1556 engraving by Agricola

 

A variety of machines were used to raise the mined ore from the pits. The simplest was the windlass, capable of raising material from relatively short distances below. The windlass was widely used in the early tin mining industry but was inefficient in that it needed two people to operate it. Developments to the windlass involving the addition of wheels and cogs allowed material to be brought up from a greater depth with less effort.

 

Horse power was also used. Harnessed horses turned vertical axles by pushing against one or more protruding cross beams. These rotated overhead barrels which carried ropes which in turn raised and lowered buckets in which the ore was drawn out of the workings. These machines are known as horse whims. The circular whim platforms of these horse engines survive in large numbers at early mining sites.

 

A 1556 engraving by Agricola showing water-powered tin stamping machinery of a type similar to that used in Cornwall at this time A 1556 engraving by Agricola showing water-powered tin stamping machinery of a type similar to that used in Cornwall at this time

 

 

Unlike the relatively pure tin ore obtained by tin streaming, lode ores required crushing and dressing. This was done in stamping mills, roughly 150 of which are known in Cornwall before 1700. The ore-bearing stones were crushed by heavy iron-headed timber beams (stamps) turned by waterwheels. The ore was reduced to a fine sand to which water was added. The resulting slime flowed through a channel to the nearby dressing floors. Here the lighter wastes were washed away in a series of wooden troughs known as buddles, allowing the heavier tin ore to settle out. This often needed to be repeated several times to concentrate the ore.

 

The processed ore was then sent to the smelter as ‘black tin’. Smelting was carried out in blowing houses, few of which now survive in Cornwall. The ore was smelted by mixing it with peat or wood charcoal and reducing it in a furnace fed with air by means of a waterwheel bellows. Finally the ingots were taken to the Stannary towns where the tin was tested for purity before being taxed.

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