Sickle Auv 322 - Late Bronze Age - Switzerland

Sickle Auv 322

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, matte, thin, discontinuous, compact, powdery, very soft 
CP2 Corrosion product Black, matte, thin, discontinuous, compact, powdery, very soft
CP3 Corrosion product Extra light grey, matte, thin, discontinuous, compact, powdery, hard
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. 7: Stratigraphic representation of the corrosion structure of the sickle observed macroscopically under binocular microscope using the MiCorr application with reference to Fig. 6. 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).

XRF analyses of the sickle were carried out on five representative areas (Fig. 4). Points 1 and 2 were done in the brown corrosion layer of each side (CP1), points 3 and 4 on the black corrosion layer of each side (CP2), and point 5 in the extra light grey of side A (CP3). All strata (soil, corrosion products, and metal) are analyzed at the same time.

The metal is presumably a tin bronze alloy with some As, Pb and Sb. The other elements detected are : S, Al, Si, Ni, Ag, Bi, P.

Results of points 1, 2 and 5 are very similar and give concentrations close to those of the remaining metal surface.

Results of points 3 and 4 are similar but different from those of points 1, 2 and 5: they indicate an enrichment in S and the depletion in Cu.

Elements (mass %) Cu Sn S As Pb Al Sb Si Ni Ag Bi P Fe
 
  % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ % +/-2σ TOTAL
1 83.1 0.1 7.3 0.04 2.0 0.02 2.0 0.04 1.6 0.03 1.0 0.08 0.9 0.02 0.8 0.03 0.5 0.02 0.4 0.01 0.1 0.01 0.1 0.01 0.1 0.01 99.7
2 83.2 0.1 7.8 0.04 2.6 0.02 1.4 0.03 1.0 0.02 0.8 0.07 0.9 0.02 1.1 0.03 0.4 0.01 0.3 0.01 0.1 0.01 0.1 0.01 0.1 0.01 99.8
3 72.0 0.15 7.3 0.04 11.4 0.06 1.3 0.03 1.1 0.02 1.5 0.15 0.9 0.02 3.4 0.08 0.5 0.02 0.3 0.01 0.1 0.01 0.1 0.02 0.2 0.01 100.1
4 70.8 0.15 8.6 0.05 10.6 0.07 1.7 0.04 2.3 0.03 0.8 0.15 0.8 0.02 2.7 0.08 0.4 0.01 0.3 0.01 0.1 0.01 0.4 0.03 0.3 0.02 99.8
5 80.7 0.2 7.6 0.05 1.6 0.04 1.7 0.04 1.6 0.03 1.5 0.02 0.9 0.03 2.0 0.08 0.4 0.02 0.4 0.01 0.1 0.01 0.1 0.02 1.1 0.02 99.7

Table 2: Chemical composition of the surface of the pin at five representative points shown in Fig. 4, Method of analysis: XRF.

None.

Complementary information

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

The appearance of CP1 and CP2 and their composition (Cu, S) seem to indicate that they might be chalcocite or djurleite.

Complementary information

According to Rychner (1987), the dark corrosion layer (CP1) was previously analysed by XRD, it was identified as a mix of chalcocite (Cu2S) and djurleite (Cu1.93S).

The corrosion structure has only been documented in binocular mode (Fig. 7).

The sickle is made from a tin bronze. The XRF analysis shows that the black corrosion layer CP2 has higher %S and lower %Cu, it would indicate the presence of black copper sulfide such as chalcocite (Cu2S) and djurleite (Cu1.93S), as described by Rychner (1987).

References on object and sample

Object files in MiCorr

1.    MiCorr_Sickle Auv-310
2.    MiCorr_Sickle Auv-313

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.