MINING

Medieval

Substances commonly mined in the medieval period included the ores of iron, copper, zinc, tin and lead, gold, silver, marble and other stones, salt and vermillion. Many of these substances can be used more or less directly, but the ores need to be smelted to extract the metal. The exceptions are gold and silver, which are found as metals of varying purity, not as ores, and zinc ore, which is used in its natural state to make brass, rather than being smelted to produce the solid metal. Salt is rather more valuable in medieval times than is apparent today, as soaking in brine was one of the few ways of preserving edible food for long periods of time.

A number of different ways of constructing mines existed. The simplest, of course, is the open cast mine, in which the material is simply removed from the surface of the land. Digging anything more complicated than this raises a number of problems, and mining remained a very hazardous profession. The most obvious danger is that of collapse or landslides, which restricted the possible shape and depth of mines. Secondly, the mine must be ventilated so that the miners do not suffocate in the enclosed space, and any noxious fumes released from the rock can be released rapidly. Thirdly, except in desert regions, mines of any significant depth (say, 300 feet, although this will vary with the climate) will tend to flood with water seeping out of the rock. Even an open cast mine will likely require some drainage tunnels to prevent it filling with rainwater! Fantasy GMs may wish to note that the same problems will occur in dungeons or other underground complexes...

Most medieval mines consisted of a vertical shaft from three to ten feet across, with a series of horizontal passages at the base extending up to 2,500 feet through the rock. An alternative design is the 'pillar and stall' mine, in which a flattened open space is dug through the mineral vein, with pillar-shaped sections being left intact to hold up the roof. These spaces can typically reach 150 feet or so across. An additional sloping tunnel was often dug to intercept the vertical one; a fire could then be placed near the base of the slope to aid ventilation.

Piston-pumps could raise water only about 24 feet, although they were used in shallower mines, as was the simple (but labour intensive!) process of bailing the water out with a chain of buckets. Water wheels cranked by hand or operated by treadmills were much more effective, being able to raise water as much as 100 feet. It was this which generally limited the maximum depth of medieval mines.

Access to the mine would be through ladders, or tree-trunks with steps cut into them. Crank handled windlasses could be used to haul the minerals out, along with wheeled barrows, and horse or dog pulled sledges.

Renaissance Developments

The basic structure of mines and the minerals extracted from them changed little, but technology helped to ease the problems of ventilation and flooding. Revolving fans, operated by hand or even by water wheels, were commonly used to keep the air moving. Linked series of piston pumps were also used, raising the water a step at a time, and powered by a water wheel at the surface. Rag and chain pumps, consisting of balls of rags that soak up water and are then pulled to the surface by chains and squeezed dry, also proved much more effective than earlier technologies and allowed much deeper mines to be constructed.