Naima. Gutknecht (HE-Arc CR, Neuchâtel, Neuchâtel, Switzerland) & Rémy. Léopold (HE-Arc CR, Neuchâtel, Neuchâtel, Switzerland) & Domon Beuret. Emmanuelle (Laténium, Neuchâtel, Neuchâtel, Switzerland)
Pin with decorated head and round section. Locally a dense and smooth olive green stratum is preserved, while green corrosion products develop on the underlying metal (Figs. 1-3). Dimensions: L = 19.0cm; WT = 12.4g.
Hauterive - Champréveyres, Neuchâtel, Neuchâtel, Switzerland
Excavation 1983-1985, object from layer 1
Late Bronze Age
Laténium, Neuchâtel, Neuchâtel
Laténium, Neuchâtel, Neuchâtel
The object was analyzed in 1987 by Schweizer. Documentation of the strata in binocular mode of the object was performed in 2022.
The schematic representation below gives an overview of the corrosion structure encountered on the pin from a first visual macroscopic observation.
|Strata||Type of stratum||Principal characteristics|
|CP1||Corrosion product||Light green, thin, scattered, non compact, very soft|
|CP2||Corrosion product||Dark green, thin, scattered, compact, very soft|
|CP3||Corrosion product||Dark brown, medium, discontinuous, compact, hard|
|CP4||Corrosion product||Olive green, medium, discontinuous, compact, hard|
|M1||Metal||Yellow, metallic, compact, hard|
Table 1: Description of the principal characteristics of the strata as observed under binocular and described according to Bertholon's method.
No sample has been taken. The observation and analysis were performed directly on the object.
XRF with handheld portable X-ray fluorescence spectrometer (NITON XL5). General Metal mode, acquisition time 60s (filters: Li20/Lo20/M20).
XRF analysis was carried out on two representative areas of the surface (Fig. 4). Point 1 was performed on a lacuna of the olive green corrosion layer and point 2 on the olive green corrosion layer (CP4 of Fig. 5).
The metal is presumably a tin bronze alloy with proabably some Sb and As and traces of Pb and Ag. The other elements detected are: S, Fe, Si, Zn.
Results of point 2 are very different from those of point 1, they indicate the enrichment in Fe and in S and depletion in Cu.
|%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ|
Table 2: Chemical composition of the surface of the pin at two representative areas shown in Fig. 5. Method of analysis: XRF.
CP4 (dense, smooth olive green stratum) is enriched with Fe and S and depleted in Cu. It seems to correspond to chalcopyrite (CuFeS2).
lake patina (Schweizer 1994)
In the article "Bronze objects from Lake sites: from patina to bibliography. In: Ancient and historic metals, conservation and scientific research" (Schweizer 1994), the corrosion products of the pin 3071 (LAB MAH 85-194) were analysed with XRD. The results show that the pin contains sulfosalt (sinnerite Cu6As4S9) and copper carbonate (malachite Cu2(CO3)(OH)2) as well as copper iron sulfide (chalcopyrite CuFeS2). Sinnerite appears as dark cristals, malachite as green cristals and chalcopyrite as a brown smooth layer.
The corrosion structure has only been documented in binocular mode (Figs. 6 & 7).
The pin is made from a tin bronze with possibly some Sb and As. It has been extensively documented by Schweizer to establish the lake and terrestrial patina typologies in his research paper from 1994. Chalcopyrite indicates a lake patina that was generated by the presence of sulfato-reducing bacteria in the burial environment and copper carbonate refers to a terrestrial patina.
References on object and sample
Object files in MiCorr
1. MiCorr_Pin or needle fragment HR-3031
2. MiCorr_Tang fragment of a knife HR-6567
3. MiCorr_Tang fragment of a knife HR-6246
4. MiCorr_Pin HR-18152
5. MiCorr_Pin HR-17773
6. MiCorr_PIN HR-18603
7. MiCorr_Pin HR-3389
8. Rychner-Faraggi A-M. (1993) Hauterive – Champréveyres 9. Métal et parure au Bronze final. Archéologie neuchâteloise, 17 (Neuchâtel), pl. 61/65.
9. Hochuli, S. et al. (1988) SPM III Bronzezeit , Verlag Schweizerische Gesellschaft für Ur- und Frühgschichte Basel, 76-77, 379.
10. Empa Report 137 695/1991, P.O. Boll.
11. Rapport d'examen, Lab. Musées d'Art et d'Histoire, Geneva GE, 87-194 à 87-197.
12. Schweizer, F. (1994) Bronze objects from Lake sites: from patina to bibliography. In: Ancient and historic metals, conservation and scientific research (eds. Scott, D.A., Podany, J. and Considine B.B.), The Getty Conservation Institute, 33-50.
References on analytic methods and interpretation
13. Robbiola, L., Blengino, J-M., Fiaud, C. (1998) Morphology and mechanisms of formation of natural patinas on archaeological Cu-Sn alloys, Corrosion Science, 40, 12, 2083-2111.