Sickle Auv 313 - Late Bronze Age - Switzerland

Sickle Auv 313

Rémy. Léopold (HE-Arc CR, Neuchâtel, Neuchâtel, Switzerland)

Complementary information

The object was documented in 1987 by Valentin Rychner. Documentation of the strata in binocular mode on the object was performed in 2022. 

The schematic representation below gives an overview of the corrosion structure encountered on the sickle from a first visual macroscopic observation.

Strata Type of stratum Principal characteristics
CP1 Corrosion product Brown, pearly, thin, discontinuous, compact, brittle, very soft 
CP2 Corrosion product Extra light grey, matte, thin, discontinuous, compact, powdery, soft
CP3 Corrosion product Black, matte, thin, discontinuous, compact, powdery, very soft
M1 Metal Yellow, thick, metallic, continuous, compact, tough, very hard

Table 1: Description of the principal characteristics of the strata as observed under binocular and described according to Bertholon's method.

Fig. 9: Stratigraphic representation of the corrosion structure of the sickle observed macroscopically under binocular microscope using the MiCorr application with reference to Fig. 8. The characteristics of the strata, such as discontinuity, are accessible by clicking on the drawing that redirects you to the search tool by stratigraphy representation, credit: MiCorr_HE-Arc CR, L.Rémy.

Complementary information

None. 

Analyses performed:

Non-invasive approach

XRF with handled portable X-ray fluorescence spectrometer (NITON XL5), General Metal mode, acquisition time 60s (filters: Li20/Lo20/M20).

The XRF analyses of the sickle were carried out on seven representative areas (Fig. 6). Points 1 and 2 were done in the brown corrosion layer of each side (CP1), points 3 and 4 on yellow areas covered with dark-grey corrosion layer (CP2 and CP3), points 5 and 6 on the magenta-blue corrosion layer (CP1), and point 7 on a black corrosion layer (CP1). All strata (soil, corrosion products, and metal) are analyzed at the same time.

The metal is presumably a tin bronze alloy with some As, Sb and Pb.  The other elements detected are : Fe, S, Si, Al, Zn and Ag (points 3 and 4).

Results of points 1, 2, 5, 6 and 7 are different and indicate the depletion in Cu and Sn and the enrichment in Fe and S.

Elements (mass %) Cu Fe S Sn
Si Al Sb Zn Pb As Ag  
  % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ TOTAL
1 54.7 0.09 17.7 0.06 20.1 0.05 3.9 0.02 2.0 0.05 0.7 0.09 0.3 0.01 0.3 0.02 <LD <LD <LD <LD <LD <LD 99.7
2 51.4 0.07 17.2 0.05 26.6 0.05 3.6 0.02 0.4 0.02 0.3 0.07 0.3 0.01 0.1 0.01 <LD <LD <LD <LD <LD <LD 99.9
3 81.4 0.17 1.2 0.03 3.9 0.05 8.0 0.05 2.9 0.1 <LD <LD 0.5 0.02 <LD <LD 0.6 0.02 0.7 0.03 0.1 0.01 99.3
4 83.4 0.12 0.2 0.01 2.3 0.03 8.3 0.04 3.0 0.08 0.2 0.1 0.5 0.01 <LD <LD 0.6 0.02 0.8 0.03 0.1 0.01 99.4
5 52.5 0.08 17.8 0.05 25.1 0.05 2.9 0.02 0.9 0.03 0.4 0.07 0.2 0.01 0.1 0.01 <LD <LD <LD <LD 0.1 0.01 100.0
6 52.4 0.08 17.4 0.06 24.5 0.05 4.3 0.02 0.5 0.02 0.3 0.07 0.3 0.01 0.1 0.01 <LD <LD <LD <LD 0.1 0.01 99.9
7 51.4 0.08 18.7 0.05 25.2 0.05 3.3 0.02 0.6 0.03 0.4 0.07 0.3 0.01 0.1 0.01 <LD <LD <LD <LD 0.1 0.01 100.1

Table 2: Chemical composition of the surface of the pin at seven representative points shown in Fig. 6, Method of analysis: XRF.

None.

Complementary information

Rychner (1987) indicates that the metal of the object is bronze. 

The appearance of CP1 and its composition (Cu, Fe, S) seem to indicate that it is either itaite or chalcopyrite.

Complementary information

According to Rychner (1987), the surface of the object is covered with itaite (Cu5FeS6).

The corrosion structure has only been documented in binocular mode (Fig. 9).

The sickle is made from a tin bronze. The XRF analysis show that the brown, purple and black corrosion layers (CP1) have higher %Fe and %S and lower % Cu and %Sn than the layer closer to the metal. It would indicate that CP1 is made of copper iron sulfide like itaite (Cu5FeS6) or chalcopyrite (CuFeS2) as described by Rychner (1987). According to Schweizer's paper from 1994, it would mean that CP1 could be a lake patina which was generated on the metal by the presence of sulfate-reducing bacteria in the burial environment.

References on object and sample

Object files in MiCorr

1.    MiCorr_Sickle Auv-310
2.    MiCorr_Sickle Auv-322

References object

3. Rychner, V. (1987) Auvernier 1968-1975: le mobilier métallique du Bronze final Formes et techniques. In: Cahiers d´archéologie romande 37, Auvernier 6. 39-40.
4. Rapport d'examen, Lab. Musées d'Art et d'Histoire, Geneva GE, 87-194 à 87-197.
5. 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, 143-157.