Historical German industry
Mining in the Upper Harz region of central Germany was a major industry for several centuries, especially for the production of silver, lead, copper, and, latterly, zinc as well. Great wealth was accumulated from the mining of silver from the 16th to the 19th centuries, as well as from important technical inventions. The centre of the mining industry was the group of seven Upper Harz mining towns of Clausthal, Zellerfeld, Sankt Andreasberg, Wildemann, Grund, Lautenthal und Altenau.
History.
The Upper Harz was once one of the most important mining regions in Germany. The major products of its mines were silver, copper, lead, iron and, from the 19th century, zinc as well. The main source of income, however, was silver. From the 16th to the middle of the 19th centuries about 40–50% of the entire German silver production originated in the Upper Harz. The taxes raised from this contributed significantly to the revenue of the royal houses in Hanover and Brunswick-Wolfenbüttel and helped to secure their positions of power and influence within the empire.
Its lucrativeness justified a high commitment in terms of investment and effort. The Upper Harz mining industry produced a considerable number of innovations and inventions, including such important advances as the man engine, the water-column engine and the wire cable.
In the Upper Harz, vein mining ("Gangerzbergbau") predominated. Excavation followed the almost vertically standing lodes or veins ("Erzgängen") downwards. In their heyday the Upper Harz Mines were among the deepest in the world. For example, as early as 1700 or so shafts were already exceeding depths of 300 metres and, around 1830, a depth of 600 metres was achieved – which was considered significant at that time because it was below sea level.
The Middle Ages.
Mining activity in the Harz goes back to the 10th and 11th centuries. The first water wheels to supply energy to the mines were constructed in the 13th century in the Pandelbach valley southeast of Seesen. At that time mining, including this early use of water systems, was carried out by the Cistercian abbey of Walkenried. At first outcropping lodes on the surface of the ground were sought out and sections of ore near the surface were dug out with hammers and chisels. Mining first boomed between 1200 and 1360. In the upper workings there were particularly rich veins of silver ore (up to 9% Ag).
Plague epidemics during the Middle Ages depopulated the Harz to a great extent and almost brought mining operations to a standstill. Another factor was probably that mining had reached its technical limits at the time with depths of up to about 60 m.
Early Modern Period to the Industrial Revolution.
A clear recovery followed from about 1520 onwards, initially at the instigation of the Duke of Brunswick-Wolfenbüttel, Henry the Younger. But it was his son, Julius, Duke of Brunswick-Lüneburg, who gave added impetus to existing mining operations in the Upper Harz and initiated the creation of further infrastructure, especially the structures of the Upper Harz Water Regale to provide water power for the mines. In order to entice the necessary labourers, tradesmen and even mining companies to the Harz, the dukes granted 'mining freedoms' ("Bergfreiheiten") based on Bohemian and Saxon practice.
Because the considerable energy needed to drain the mines increased as the mines became deeper and deeper, attempts were made early on to reduce energy consumption by driving drainage adits. This entailed cutting tunnels from the mine into the neighbouring valleys, through which water could drain away downhill under gravity. The deeper the water level lay, the longer these adits needed to be. The longest of these tunnels was the Ernst August Tunnel, built in the mid-19th century, which was 26 kilometres long. It collected water from the mines in Bockswiese, Lautenthal, Zellerfeld, Clausthal and Wildemann and transported it to Gittelde on the edge of the Harz.
The Upper Harz mines attained their greatest productivity in the 16th and 17th centuries, even though there were frequent crises during that time. In 1690 the metal produced reached a quantity that was not exceeded until 1850. That was especially thanks to the construction of artificial water supply structures and the introduction of gunpowder for rock blasting from 1630 onwards. During the course of the 18th century there were constant crises as a result of the lack of wood. The problem was eased by the introduction of coking coal for the smelters around 1800. On 1 January 1864 the mines were nationalised by the Kingdom of Hanover.
Industrial Revolution to the Closure of the Mines.
Following the annexation of the Kingdom of Hanover by the Kingdom of Prussia in 1866 the Royal Prussian Mining Inspectorate ("Königlich-Preußische Bergbauinspektion") took over the running of mines in the Upper Harz. It was succeeded in 1924 by Preussag. Around 1900 shaft depths of 1,000 metres were reached and the mining of ore became increasingly costly. At the same time the mines had to compete with other domestic and foreign mines in a climate of ever-improving transportation. Overexploitation during the First World War and plummeting metal prices resulted in major closures at the height of the Great Depression in 1930, when the big mines around Clausthal-Zellerfeld, Bockswiese and Lautenthal had to close. Mining operations continued in Bad Grund, however, until 1992.
Re-use for electricity generation.
Following the closure of the mines in 1930, several shafts switched to the generation of electricity. Here, water from the Upper Harz Water Regale's network of ponds and channels was transported down chutes into the shafts, in which turbines were driven to produce electricity at the level of the deepest drainage adit. The generation of electricity was carried out by Preussag until 1980 in the Kaiser Wilhelm (maximum output 4.5 MW) and Ottiliae (maximum output 1.5 MW) shafts. The hydropower stations were closed in the early 1980s when the water rights expired and the profitability of the power stations continued to fall at a time of sharply rising wages and stagnating electricity prices. These years saw the permanent closure of the last surviving mines.
Mining technology in the Upper Harz.
Mining the ore.
In the early days of mining in the Upper Harz simple open cast working ("Schurfe") was the predominant method of mining. With increasing depth a form of mixed mining developed that was somewhere between open cast and underground mining. These mines were known as glory holes ("Pingen") or simply dip mines ("Unterwerksbau"). The ore deposits that lay immediately on the surface were quickly exhausted and, as early as the 12th and 13th century miners were forced to switch entirely over to underground mining. The mining methods that could be used were limited by the steep, almost vertical, lenticles of ore, which were only a few metres wide, but dipped for several hundred metres into the earth. Hauling shafts were usually positioned in centre of the ore allotment on the lode and followed it into the ground. This resulted in inclined shafts with their characteristic, right-angled, longitudinal sections and frequent changes of angle away from the vertical. There were two reasons for this approach: firstly, it had to be possible to extract ore from the beginning (as soon as the shaft was sunk) in order to make the pit economic as early as possible. Secondly, the rock in the ore lode, which formed a 'zone of disturbance', was much softer than the surrounding rock. The typical Harz grauwacke was far harder than concrete. As a result, the majority of drainage adits followed the vein. From the shaft, main gangways, the so-called "Feldortstrecken", were driven out to the boundary of the mine allotment. From these gangways, miners began to extract the ore, heading downwards into the floor, by 'brushing down' ("Nachreißen") in stepped fashion, a technique known as underhand stoping. The stopes had a height of up to 3 metres and followed one another about 5 to 6 metres apart. In longitudinal section, therefore, a pit looked like a Christmas tree standing on its head. The deepest point of the pit was usually the main shaft. This enabled it to collect pit water in the shaft 'sump'. As mining progressed the shaft was sunk deeper.
The packing (gangue material used for filling) from the upper main gangways was placed in the exhausted cavities (the so-called 'old man' or "Alter Mann"). This required the erection of a wooden ceiling over the active workings so that packing material did not fall into it and onto the face workers there. If the expected supply of ore or its quality did not justify sinking the main shaft deeper, or if the workings were a long way from it, draw-shafts were sunk. These blind shafts saved having to pack the 'old man'. In the Hornstatt, 1 or 2 labourers ("Knechte") worked a hand winch and lifted the ore to the next highest main gallery.
From 1633 gunpowder was used both for ore extraction and for driving gangways. This increased the daily headway considerably, from a few centimetres into the lode to a metre or more. The disadvantage, however, was that even more wood was needed to extend the mine, because blasting caused the rock to fissure. When blasting, first a cut in the lode was made about 3 metres high and deep and a little less than a metre wide using hammer and chisel. Next one or two transverse boreholes with a 6–7 cm diameter were drilled by hand Usually two-man boring was employed: one turned the borer whilst a second hit it with his sledge. The holes were filled with gunpowder and stuffed with a wooden peg which had a hole for a slow-match wick. Unlike blasting with modern explosive, the stemming had to be wedged in using an iron rod centred on the borehole and a thick wooden prop in a slot ("Bühnloch") on the opposite side. This operation frequently led to serious accidents when the gunpowder self-ignited as a result of friction-generated heat. Normal detonation was carried out using cord that had been impregnated with sulphur and gunpowder.
After clearing the blast debris, the material to be screened was loaded into wagons ("Hunde" or "Hunte") using rakes ("Kratze") and tubs ("Trog"). Larger boulders ("Wände") were first broken up with sledges and crowbars.
From the second half of the 18th century the method of mining was reversed. Now the roof was always mined and so extraction proceeded upwards. That meant the miners worked on top of the packing and could transport the ore under gravity using so-called chute holes ("Rollöcher" or "Rollen") rather than shafts. Overhand stoping remained the only mining method in the Upper Harz mines until the end and was perfected in the final years through the use of trackless wagons, roof bolts
("Ankern"), shotcrete and lean concrete packing. Trials with sublevel stoping ("Teilsohlenbruchbau") and square set timbering ("Blockbau mit Rahmenzimmerung") did not get past the experimental stage.
In the middle of the 19th century, the many individual pits transferred to larger mine complexes with central shafts, at which point the sinking of inclined shafts and the mixing of layout and equipment with the workings was abandoned entirely. The central, vertical shafts lay in the host rock (usually in the hanging wall), just as permanently established as the main gangways (usually in the footwall).
Extraction technology.
To begin with the ore was chiseled free and carted to the surface of the open pits or shallow mines in baskets. Once shaft depths increased to between about 10–60 metres hand winches ("Handhäspel") were used, operated by one or two workers ("Knechten"). The crude ore was placed in wooden buckets for transportation. For the rather short, horizontal gangways leading to the shaft the ore was carried in "Trogs" for several centuries (long before the introduction of blasting). In the 17th century the shafts reached depths of between 100 and 200 m. Ore could no longer be removed by hand and horsepower was increasingly used. The horses worked in a cone-shaped building, the "Göpel" or "Gaipel", which housed a horse whim, a winch that was driven by the horses walking in a circle. The hauling cable (made of natural fibre) or cast-iron chain was wound up and down over a vertical axle. The cable was routed down the shaft and hauled barrels of ore up and down. Due to the shaft's incline, barrels were covered with iron runners on one side, resting partly on the side of the shaft. Above ground at the pithead the ore was emptied out and transported away