The "Karth" - A Roman gold mining district in the Eastern Alps (Austria)

The Karth is a wooded plateau to the south-east of the town of Neunkirchen in southern Lower Austria. The still clearly visible remains of Roman gold mining are large reservoirs and leats, up to 25 km long aqueducts, that brought water to the mining fields. Mining placer deposits with the help of the power of water (hydraulic mining) is a typically Roman mining technique, that is described by Plinius the Elder in his Natural History. Water is stored in reservoirs above the deposit, when the sluice gates are opened the torrent of water breaks up the deposit. The sediments accumulating at the bottom of the deposit can then be washed to obtain the gold. Not only the remains still visible in the countryside, but also numerous Roman finds made in the past decades, attest to a dating to the Roman period. The aim of the project is the interdisciplinary study of this unique site, which is the only Roman gold mine known in the Eastern Alps. Detailed studies of LiDAR scans and extensive field walking will be carried out to identify all remains of Roman mining. Geophysical prospection of the reservoirs and the settlement sites not only serve the planning of the archaeological excavations but also help to understand sites that cannot be excavated. Archaeological excavations at the reservoirs and the leats will be done to understand their geometry, for example the capacity of the reservoirs, the construction of the sluice gates, through which the water was led over the deposit, and their general construction, for example the sealing of the base. The settlement sites will also be excavated. The features as well as archaeological finds will give evidence of the living condituions of the miners. Geological studies will be undertaken parallel to the field survey and the archaeological excavations in order to study the gold content of the deposit and to differentiate between natural and anthropogen deposition of sediments. The capacity and functioning of the leat system will be studied from hydrological and hydraulic view points in order to better understand the frequency and intensity of the hushing. The aim of palaeobotanical studies (pollenanalyse) together with the reconstruction of the original topography is the reconstruction of the origianl environment and the documentation of environmental changes due to Roman mining activity. Library studies to catalogue Roman sites in the vicinity of the mining district will put the Roman gold mining in a socio-economic context. All in alltThis interdisciplinars project yields substantial contributions to the knowledge of Roman hydraulic mining.

The Karth is a region near the town of Neunkirchen in Lower Austria, about 70 km to the south of Vienna. Here the Romans mined a secondary deposit called Loipersbach -Formation, in which flakes of gold are randomly distributed. The gold was mined by hydraulic mining as described by Pliny the Elder in the 33rd book of his Natural History. Aqueducts, which are known as "leats" in a mining context, were built to conduct water to large tanks a bove the deposit. After the surface of the deposit was cleared of vegetation and overburden, the sluice gates of the tanks were opened, and water was led over the deposit to erode it. In a final step the sediment was washed over a bed of heather to obtain the gold. Since the Karth was never used for agriculture and is heavily forested, the remains of Roman gold mining are exceptionally well preserved. Five leats of a total length of about 123 km led to the eleven individual mines with their tanks. Seventeen large tanks and numerous smaller tanks have been documented. The mining area, together with the catchment area of the leats, covers approximately 147 km2. The mines are characterised by steep, heavily eroded gullies with large tanks at the top, the largest measuring approximately 80 by 44 m. Each tank has one inlet for the leat and one or more outlets towards the mining area. Today, the walls of the tanks are preserved nearly at their original height. The leats begin at a brook or river and follow the contour of the valleys with a consistent low gradient, collecting additional water from streams en route until they arrive at the tanks. In many parts, they can still be seen as well -preserved channels. Archaeological excavations were carried out in two tanks and sections of the leats were also documented in order to study their construction. In addition to archaeological excavations and intensive field-survey, gold-washing as described by Pliny was reconstructed as an experiment. A wooden sluice-box, its bottom lined with heather, was then installed in a brook. For quality control a modern sluice-box was set up downstream from the reconstructed Roman one. The heavy mineral concentrate accumulated in the heather was then washed in a pan. The Roman method proved to be highly effective. No gold was found in the modern sluice-box. On the start page of the project website (www.karthgold.com) two professional videos can be viewed. One is about the project in general and the second one on the gold - washing experiment. The website also contains numerous pictures in the gallery and pdfs of articles on the project can be downloaded.