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. It has olive green and dark brown corrosion products (Figs. 1-4). Dimensions: L = 5.9cm; WT = 3.3g.
Hauterive - Champréveyres, Neuchâtel, Neuchâtel, Switzerland
Excavation in 1983-1985, layer 3
Late Bronze Age
Laténium, Neuchâtel, Neuchâtel
Laténium, Neuchâtel, Neuchâtel
The object was kept in wooden storage, No intervention documented.
No intervention documented, but a resineous material is present on the surface which indicate that a consolidation was made. 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|
|NMM1||Non-metallic material||Transparent, thin, compact, only present in CP1|
|CP1||Corrosion product||Olive green, thick, discontinuous, compact, hard|
|CP2||Corrosion product||Black, veins shape, thin, discontinuous, compact, hard|
|CP3||Corrosion product||Dark brown, thin, continuous, compact, hard|
|M1||Metal||Dark yellow, thick, metallic, 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).
The XRF analysis of the pin was carried out on three representative areas of the surface (Fig. 5). Point 1 was performed on the residual metal, point 2 on the smooth and dense olive green stratum (CP1) and point 3 on the underlying black layer (CP2).
The metal is presumably a tin bronze alloy with possibly some As, Sb, Pb and Ni. The others elements detected are: S, Fe, Si, Al, Co, P, Ag.
Results of point 2 indicate the enrichment in Fe and in S and the depletion in Cu and in Sn typical of lake patina (chalcopyrite).
Results of point 3 indicate a slight enrichment in Sn and depletion in Cu.
|%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||Total|
Table 2: Chemical composition of the surface of the pin at three representative areas shown in Fig. 5, Method of analysis: XRF.
Based on Schweizer analyses and results from table 2 CP1 of Fig. 6 should be chalcopyrite.
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 3389 (LAB MAH 85-28) were studied through XRD. The results show that the pin contains copper iron sulfide (chalcopyrite).
The corrosion structure has only been documented in binocular mode (Figs. 7 and 8).
This pin is made from a tin bronze with possibly some As, Sb, Pb and Ni. It has been extensively documented by Schweizer to establish the lake and terrestrial patina typologies (1994). One third of the surface is still covered with a stratum analysed as lake patina (chalcopyrite), generated by the presence of sulfate-reducing bacteria in the burial environment.
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-3071
6. MiCorr_PIN HR-17773
7. MiCorr_Pin HR-18603
8. RychRychner-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.