Metal Mining ::
The principal metal mined in the UK is lead. Lead is usually found in near-vertical veins up to 4 metres in thickness which were intruded into fractured limestone, sandstone and chert which usually forms higher ground.
The mineralisation took place between 100 and 200 million years after the rock was deposited, hot mineral rich fluids rising from molten igneous rock at depth exploiting the faults and fractures in the host rock. Other minerals found in conjunction with lead were zinc and silver.
All three were mined, and separated afterwards in the refining processes.
Lead veins were worked initially at outcrop to create a linear ditch feature along the line of the vein. Deeper mining in later years was by tunnels from shafts sunk to intercept the vein at depth, then working upwards in the vein towards the previous workings.
As the veins are near vertical, the outcrops and associated old shaft mounds form near-linear features across the countryside. Lead ore was raised to the surface and smelted in the coalfield, but waste material from the veins was stored on timber supports within the workings.
>> Coal Mining for information on coal mining.
>> Investigation for information on research, investigation and remedial work.
>> Mineshafts for information on mineshaft hazards.
(centre) this photograph shows an open stope approximately 2 metres wide where all the mineral has been removed. Just visible spanning the void is one surviving timber support, one of many which would have supported a timber platform onto which mining debris was stacked.
(right) this old plan of 1904 shows the north-west to south-east orientation of three parallel lead veins known as the Branch Vein, the Holway Vein, and the South Joint, at the Plantation Mine in Gorsedd, Holywell. The coloured tunnels are main haulage roads at different depths within the veins, which dip to the north-east. The vein outcrops are not shown, but will be south-west of the shallowest haulage road in each vein. Old workings were encountered in the two southern veins above the 70 Yard Level.
(centre) this photograph shows an open stope approximately 2 metres wide where all the mineral has been removed. Just visible spanning the void is one surviving timber support, one of many which would have supported a timber platform onto which mining debris was stacked.
(right) this old plan of 1904 shows the north-west to south-east orientation of three parallel lead veins known as the Branch Vein, the Holway Vein, and the South Joint, at the Plantation Mine in Gorsedd, Holywell. The coloured tunnels are main haulage roads at different depths within the veins, which dip to the north-east. The vein outcrops are not shown, but will be south-west of the shallowest haulage road in each vein. Old workings were encountered in the two southern veins above the 70 Yard Level.