3.1. Mining Methods
After the potential gold area has been 'discovered' by 'bush' prospectors, something that occurs mostly misadvertently than by design, the first task is to get to the ore body. This is done by sinking prospecting pits which approximately measure 1.5 metres by 2.0 metres (or even less). These pits later on develop into a shaft which serves as man-way and for the hoisting of ore, waste and supplies.
The waste material is not transported away but is piled up around the mine shaft opening. The shaft develops to depths of between 15 metres and 100 metres in some cases. Deeper shafts were observed in Nyabigena mines, Mugusu and Nyarugusu. At Ushirombo, mines are found only at shallow depths due to a high water table which cannot be drained efficiently.
Mine support is achieved through the use of timber which is usually obtained from the surrounding forests. At Nyabigena, where the rock is able to withstand the mining operations, timbering is not used. In Ushirombo mine, timbering is used extensively due to poor rock competence and the presence of underground water.
Tools used for rock excavation are very simple and include picks, shovels, hammers, wedges, and sharpened steel rods. These tools were employed in all the artisanal mining areas visited. In areas such as Nyabigena, one miner had his own compressor, generator, water pump, drilling accessories and employed explosives for underground rock breaking. However, most artisanal miners use hand tools as shown in Figure 1.
The hoisting of materials from an underground mine to the surface is done by simple timber fabrications whereby two V-like timber posts are erected on both sides of the shaft. A timber log on which sisal or tree-bark rope is wound is placed in between the two poles. The log is then turned manually to elevate or descend the rope which is fitted to a leather sack for hoisting ore and waste or to a 25-50 litre bucket for mine drainage. The most common hoisting arrangement is illustrated in Figure 2.
It was generally observed that ventilation was poor, which raises an issue of concern as the depth of the mines would demand proper and adequate ventilation. However, a single shaft is used in most of these mining activities; which means that natural ventilation does not occur easily. In most cases, the air supply is improved when a heading connects two mine shafts thereby creating a natural draught.
Lighting for the underground mine is generally done using torches powered by dry batteries (two 1.5 volts batteries connected in series). This is a normal practice at Nyabigena, Nyarugusu and Mugusu. At Isungangwanda and Lusu in Nzega, the miners use small kerosene lanterns called 'koroboi'3. However, this method produces a lot of soot in the underground mines. The more advanced artisanal miners have their own power generating sets.
3A 'koroboi' consists of a small can which has a cover and into which paraffin is fed. The top cover is pierced at the centre to allow for the entry of a thin cloth dipped into the paraffin (serving to draw the paraffin up). With the tin cover in place, the end of the cloth that protrudes outside the cover is lit providing light to the miners.
Safety gears are almost non-existent in these mines. As this is a precarious occupation, one would expect miners to use boots, helmets, dust muffs, safety glasses, and have first aid kits. However, it was merely in 2% of the areas visited that miners paid some attention to the safety aspects.
Flooding in the mines is a common phenomenon. Many underground mines are abandoned not because of ore depletion, but due to excessive water inflow. This has been a major production bottleneck which most miners have failed to contend with. Those with pumps charge exorbitant fees to miners requiring such services.
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