The discovery of the prehistoric mines

When from 1311 onwards new wet salt-extraction methods of mining were used, the prehistoric mines in Hallstatt were a nuisance. The compacted rock of the Heidengebirge could even bring work to a standstill. This is why miners at the time kept exact records on where the prehistoric mines were located. Today, most of these mines they found have been crushed by the pressure of the mountain and are therefore no longer accessible. However, the location of many of them can still be traced using these medieval written documents.

Written documents on prehistoric mining
Wet salt extraction
The discovery of the Christian von Tuschwerk mine
 

Written documents on prehistoric mining

Traces of prehistoric mining have been recorded in chronicles, fascicles, travel journals, visit records, etc. In the mining industry, there have always been records concerning the old production sites. The Hallstatt records repeatedly mention finds that can only be explained by the fact of the existence of ancient mining activities of one kind or other. Initially, such discoveries were not recorded for any particular historical interest, but because they often hindered or interrupted the operation of the leaching chambers. Precise documentation is a basic pre-condition of mining.
 

Wet salt extraction

The evidence of prehistoric mining in Hallstatt was discovered by the miners themselves. They repeatedly struck and reported traces of ancient mine works dating back to prehistoric times. The most effective mining procedure in the Alpine salt deposits is 'wet mining', where salt is extracted by leaching the saline deposit layers in a top-down method. The deposit is structured into horizontal gallery systems, the so-called mining 'horizons', horizontally separated in by at least 30 meters of intervening rock. Cavities called leaching chambers are created between the horizons and filled with freshwater from the upper horizon. Only the salt gets dissolved; all other constituents are insoluble in water and settle out. One hundred litres of fresh water can absorb about 33 kg of salt. If this degree of saturation is reached, the water is drained as brine through the respective lower horizon and then flows to the evaporation unit where the solid salt is recovered.

As mining proceeded, the prehistoric zones were inevitably cut through when galleries and leaching chambers were cut, or they were revealed by the leaching process itself. Wet mining in Hallstatt has been documented since AD 1311, which means that the Hallstatt salt mine has been systematically scrutinized, as it were, for some 700 years. But while prehistoric traces present themselves in the places where salt has been historically mined, where there has been no recent activity, for whatever reason, the secrets of the mountain remain sealed. We do not know whether or not there was mining in such other areas in prehistory. The oldest document referring to traces of ancient mining is dated AD 1713, being a chronicle by Hans Riezinger. No documents relating to medieval salt mining have come down to us, although the miners in the Middle Ages must surely have stumbled repeatedly upon traces of prehistoric mining.
 

The discovery of the Christian von Tuschwerk mine

Today, these historic documents are kept in the archives of the Salinen Austria AG and in archives in Linz and Vienna. A significant part of archaeological research starts in the archives rather than in the actual mine. Margarita Pertlwieser's painstaking research in the Upper Austrian Land Registry (the OÖ Landesarchiv) uncovered a real treasure: an inspection protocol dated AD 1748 showing that an ancient old building, parts of tapers and other remains had been discovered at that time. This historic information was the key to rediscovering the location of one of the richest and most fascinating prehistoric findspots in the salt mine, the so-called 'Christian von Tusch' mine works (or Christian von Tuschwerk), now systematically investigated since 1992.

(Kowarik, K. - Reschreiter, H. - Loew, C.)
  
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