The limnic (freshwater) opals from Csaterberg were an easily accessible raw material source und have been used for chipped stone tools over a long period. This project investigates the issue in all its complexity, including paleontological-geological aspects, chronological-technological questions, and the distribution of the artefacts.



The Csaterberg is a long known and at the same time unknown site – fossilised wood was described by Carolus Clusius as early as 1583 and 1601 in the scientific literature. Most likely already in the 19th and especially in the 20th century, the hills in this region were intensely combed by mineral- and fossil collectors, which resulted in the destruction of (then unrecognised) archaeological features in the course of partly extensive digging activities. In contrast to the mineralogical and paleontological particularities, the archaeological significance of the Csaterberge has for the longest time not been recognized and remained greatly underestimated until today.

Geology and paleontology

The sedimentary Csaterberg-limnosilicite was formed at the shore of a Miocene freshwater lake. Through a cooperation with the Geological-Paleontological Dept. of the NHM, the geological age of this formation could be clarified using gastropods. According to this study, the limnosilicite dates to the Lower Turolium/lowest section of the Upper Pannonium (Harzhauser et al. 2019).

Raw material characterisation

The characterisation of the silicite is undertaken according to the MLA (Multi Layered Chert Sourcing Approach): Macro- and microscopically, and geochemically in cooperation with the University of Graz, to establish a unique geochemical fingerprint which should allow a secure differentiation from other limnosilicite/lacustrine opal varieties in eastern and southeastern Europe (Hungary: Tokaj mountains, Slovak Republic: mainly Banskobystrický kraj, Serbia: Lojanik).


The detection of quarrying sites, mining traces and knapping places of various time periods in the whole area of Hoch- and Kleincsaterberg was undertaken in the course of fossil sampling and in collaboration with private collectors. In the future, these features will be mapped in detail, and core soundings and test trenches are envisioned to test if Palaeolithic layers are preserved in situ, and if suspected Neolithic mining traces can be documented.

Artefact analyses

Morpho-technological analyses of the assemblages enable a coarse differentiation and dating of artefacts even from surface collections lacking secure stratigraphic contexts, and placing especially the Middle Palaeolithic tools in a Central European context.


Investigations concerning the diachronic distribution of the raw material and artefacts made from this limnosilicite are still in their incipient stages. Nevertheless, it already becomes apparent that ›Csaterberg-opal‹ occurs during the Upper Palaeolithic, the Neolithic and the Copper Age at a multitude of archaeological sites within a diameter of approximately 100 km. Hence, the Csaterberg raw material source is of high regional and super-regional importance.