Brixlegg – Prehistoric Mining, Beneficiation and Smelting of Copper Ores Gert Goldenberg (Text), Ulrike Töchterle (Guidance)
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Palyno-Bulletin | Volume 3 | 2015 Brixlegg – Prehistoric Mining, Beneficiation and Smelting of Copper Ores Gert Goldenberg (text), Ulrike Töchterle (guidance) Institut für Archäologien, University of Innsbruck, Langer Weg 11, A-6020 Innsbruck, Austria Introduction and extractive metallurgy based on fahlores began On the southern side of the Lower Inn Valley (North during the 12th century BC (Möslein & Winghart 2002; Tyrol) an important historic mining area for copper and Sperber 2004; Goldenberg & Rieser 2004) and contin- silver ores extends from Schwaz in the west to Brixlegg/ ued to the 8th century BC. For this period the com- Radfeld in the east, well known since the Early Modern plete operation chain for the copper production (min- Age as the famous mining region of Schwaz. Based on ing, beneficiation, smelting) could be investigated and the exploitation of copper and silver from rich fahlore documented in the mining district of Brixlegg-Zim- deposits, this part of Tyrol developed to a leading min- mermoos (Moosschrofen, Schwarzenberg Moos) and ing area in Central Europe during the 15th and 16th Radfeld (Mauken Valley; Fig. 2) (Goldenberg et al. 2012; century AD. In the course of its important economic Goldenberg 2013). success technological innovations and social acquire- ments influenced to a certain extent the societal devel- Mining opment of the European Renaissance. Referring to the In the Schwaz/Brixlegg district remains of prehistoric current state of research a comparable situation can fahlore mining are widespread (Pirkl 1961; Rieser & be expected for the same area more than 2000 years Schrattenthaler 2000; 2004; Goldenberg & Rieser 2004; earlier, during the Late Bronze Age/Early Iron Age. Goldenberg et al. 2012). Some of these near surface This prehistoric era of prosperous fahlore mining and mining cavities are known as “heathen mines” since the copper production is not recorded in written sources 16th century AD (Schwazer Bergbuch, Winkelmann and is therefore accessible only by archaeological and 1956). An outstanding monument of Late Bronze Age/ archaeometrical investigations. Within the framework Early Iron Age fahlore mining is represented by the of the Special Research Program HiMAT (The History Moosschrofen (Fig. 3). of Mining Activities in the Tyrol and Adjacent Areas – The easily accessible site shows typical structures of Impact on Environment and Human Societies), estab- exploitation in the form of surface near cupola shaped lished at the University of Innsbruck and supported by cavities resulting from fire setting (Fig. 4–6). the Austrian Science Fund (FWF) from 2007 to 2012, a This special driving technic used wood fires to break number of prehistoric mining sites in the area of Brix- down the hard dolomitic rock (Weisgerber & Willies legg-Zimmermoos and the Mauken Valley have been 2001). Radiocarbon data and finds of pottery frag- studied and documented by interdisciplinary investi- ments date the local mining activities at the Mooss- gations (Fig. 1). Radiocarbon dates and dendrochron- chrofen into the 9th/8th century BC. Actually high-res- ological data evidence mining activities from the 12th olution data is in preparation by dendrochronological to 7th century BC. investigations of charcoal remains collected from the Fahlore mining and metallurgy in the Lower Inn Val- prehistoric stratigraphy (FZ HiMAT project 2015 - 2018, ley played an important role already during the Early supported by the Austrian Science Fund FWF). Other Bronze Age. Primary copper metallurgy based on fahl- remarkable examples for Late Bronze Age/Early Iron ores from the Schwaz/Brixlegg ore deposits was per- Age fahlore mines exploited with fire setting are repre- formed in settlements like Kiechlberg/Thaur (Töch- sented by the mines Mauk B and Mauk E in the Mauken terle et al. 2012; Töchterle 2015), Tischofer Höhle/ Valley (difficult accessibility). Kufstein (Harb 2002), Buchberg/Wiesing (Martinek & Extended archaeological excavations could be real- Sydow 2004) and Mariahilfbergl/Brixlegg (Höppner et ised in the mine Mauk E. This mine is driven about al. 2005). However, the archaeological confirmation of 25 meters deep into the dolomitic host rock. The ore the related fahlore mining in the field is still a desid- exploited was antimony-rich fahlore, from which thin eratum. Referring to geochemical analyses performed veinlets (millimeter to centimeter thick) are still recog- on copper and bronze artefacts this first time of pros- nizable on fresh rock surfaces. After the first inves- perity was interrupted at the end of the Early Bronze tigation it became clear that the mine is primarily of Age and only regained importance in the Late Bronze prehistoric origin, but reworked during Early Mod- Age (Lutz & Pernicka 2013). This second rise of mining ern Times. Fortunately and due to the minor ore con- 87 Palyno-Bulletin | Volume 3 | 2015 Figure 1. The Late Bronze Age/Early Iron Age mining district Zimmermoos-Mauken Valley (Radfeld-Brixlegg) with archaeological sites (graphic: G. Hiebel; Orthophoto © Land Tirol). tent left in the dolomite, the younger works did not activities but also helps to improve the regional tree- go beyond a prospecting of the remaining ore so that ring chronology for the period under consideration! for the most part of the mine the prehistoric struc- This result delivers an excellent base for further pre- tures were preserved. The prehistoric work is charac- cise dating of a larger series of mines which is part of terized by carbon black covered rock surfaces and the the new FZ HiMAT research project already mentioned traces of fire setting as the principal driving technic. above. These are again typical cupola like cavities formed as a result of the heating effect to the dense and solid Beneficiation structure of the dolomitic host rock. The Early Modern In the former peat bog Schwarzenberg-Moos (Brix- works show bright surfaces with the cut marks from legg-Zimmermoos) traces of a Late Bronze Age ore iron tools (hammer and chisel). Parts of the Early Iron beneficiation site were discovered in 2000 in a drain- Age cavities were 3 D laser scanned in order to enable age channel and could be investigated in the frame the calculation of exploitation volumes (Hanke et al. of the SFB HiMAT program (Fig. 7). Two excavations 2012). The application of fire setting left behind fillings in 2007 and 2008 furnished excellent materials for in the mine which are rich in charcoal. By systematic the reconstruction of the site as well as for the dat- sampling and subsequent dendrochronological anal- ing by dendrochronological analysis (Goldenberg et ysis of the charcoal it was possible to get an accurate al. 2012). Here, after local forest clearing, a small work- dating of the mining activities, which in this case falls shop was installed in order to use the outflow of the in the last two decades of the 8th century BC (cutting bog water for the beneficiation process (Fig. 8). Fahl- dates from 715 to 706 BC, Pichler et al. 2012; 2013). The ore was exploited in a mine only a few hundred meters Early Modern prospecting activities in the mine Mauk distant. A kind of a washing basin with a rectangular E could also be dated by the same method to the 16th wooden structure was set up, from which the basic century AD (using wooden remains). beams could be excavated in their in situ position. In Dendrochronological analysis of charcoal from fire-set- connection to this basin, two wooden troughs were ting allows not only a precise dating of the mining uncovered and interpreted as parts of the ore washing 88 Palyno-Bulletin | Volume 3 | 2015 Figure 2. Chemical composition of fahlores (tetra- Figure 3. Moosschrofen with Late Bronze Age/Early edrite/tennantite), fahlore vein in „Schwazer Dolomit“ Iron Age fahlore mines. from the Mauken Valley. Figure 4. Late Bronze Age/Early Iron Age fahlore mine, Figure 5. Late Bronze Age/Early Iron Age fahlore mine exploited by fire setting - Moosschrofen. Mauk B: typical structures remaining from fire setting. 89 Palyno-Bulletin | Volume 3 | 2015 ing furnaces, a multiphase roasting bed and a washing plant (for crushed slags, with wooden remains) could be uncovered and documented during the excava- tions (Fig. 11). The collected archaeometallurgical material from the smelting site (ores, slags, roasting products) were ana- lysed in order to work out the raw materials and the process parameters. A section of the slag heap, consist- ing mainly of crushed slag (“slag sand”) was selected for a special excavation with the aim to collect animal bones for archaeo-zoological analysis. The remarkable preservation of organic materials (Heiss & Oeggl 2008), especially bones, is mainly due to the antibacterial effect of the remaining copper salts in the slag sedi- Figure 6. Charcoal from fire setting and pine wood ments. The recovered animal bones were suitable for spills from the Early Iron Age fahlore mine Mauk E. the reconstruction of the meet supply of the local min- ers/smelters community (Schibler et al 2011). equipment. Furthermore, a waste dump connected with the crushing of ore could be documented, con- Infrastructure and subsistence strategies taining a mortar stone in situ, fragments of hammer In the Schwaz/Brixlegg mining district, all steps of a stones, a few wooden tools and ceramic. By the sys- complete operation chain (mining, ore beneficiation, tematic dendrochronological analysis of the wooden smelting) could be documented in the area between remains an accurate dating could be achieved, which the Moosschrofen, the Schwarzenberg Moos and the shows an occupation of the site between 900 and 870 Mauken Valley (Goldenberg et al. 2012; Goldenbeg BC (Nicolussi et al. 2012). Several soil samples from the 2013). Small scale Late Bronze Age “workshop settle- prehistoric strata as well as pollen profiles from the ments” are to be expected in the immediate vicinity surrounding peat bog were collected and analysed to of the mines and the smelting site Mauk A.