Archaeological and Anthropological Sciences
https://doi.org/10.1007/s12520-019-00935-z
ORIGINAL PAPER
Archaeometric studies on early medieval silver jewellery from Central
and Eastern Europe
Ewelina Miśta-Jakubowska 1 & Renata Czech Błońska 2 & Władysław Duczko 2 & Aneta M. Gójska 1 & Paweł Kalbarczyk 3 &
Grzegorz Żabiński 4 & Krystian Trela 1
Received: 9 November 2018 / Accepted: 2 September 2019
# The Author(s) 2019
Abstract
Scanning electron microscopy with X-ray microanalyses (SEM-EDX) was used for a technological study of silver jewellery from
three hoards found in Poland. The assemblage consists of 26 artefacts from the period of formation of the first Polish state (900–
1039 AD) and can be divided into three groups: West Slavic, post-Moravian and Scandinavian. Research results provide
information concerning techniques used for granulation ornament and the provenance of raw silver. Elemental composition
changes are manifested mainly by different Cu contents. A higher Cu content was found in solder. The higher Cu content in
relation to the morphology of the joining region with visibly spilled granulation demonstrates that the West Slavic beads were
produced with the use of metallic soldering. On the other hand, other studied jewelleries are characterised by Cu, Sn, Sb and Zn
enrichments in oxidised soldering regions, which implies that they were manufactured with the use of non-metallic soldering. In
addition, studies on the provenance of the raw material were made based on the analysis of lead isotopic ratios. For this purpose,
laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used, and the obtained lead isotopic ratios were
processed using linear discriminant analysis (LDA). The isotope study demonstrates that all examined artefacts were made using
re-melted metal from multiple sources. The most probable sources of silver were ores from Uzbekistan, Afghanistan and Freiberg
(Germany).
Keywords SEM-EDX . LA-ICP-MS . Lead isotope ratios . Medieval jewellery . Silver hoards
Introduction
The aim of this paper is to discuss the results of recent research
conducted on female ornaments from early medieval hoards in
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s12520-019-00935-z) contains supplementary
material, which is available to authorized users.
* Ewelina Miśta-Jakubowska
Ewelina.Mista@ncbj.gov.pl
1
National Centre for Nuclear Research, A. Sołtana 7,
05-400 Otwock, Poland
2
Institute of Archaeology and Ethnology, Polish Academy of
Sciences, Al. Solidarności 105, 00-140 Warsaw, Poland
3
Institute of Nuclear Chemistry and Technology, Dorodna 16,
03-195 Warsaw, Poland
4
Institute of History, Jan Długosz University in Częstochowa, Al.
Armii Krajowej 36a, 42-200 Częstochowa, Poland
Poland (Dekówna 1974; Zoll-Adamikowa et al. 1999).
Assemblages consisting of coins and other kinds of silver artefacts are important historical source materials from which it is
possible to obtain data about economic, political and social
conditions of people who were depositing silver. These issues
are crucial for understanding the relations between early states
in Central Europe, mainly between the first Polish state created
by the Piast Dynasty, the Czech state and Scandinavian countries. The custom of deposition of silver and gold artefacts in the
form of hoards was of Scandinavian origin and went into use in
Piast Poland, but not in the Czech lands ruled by the Přemyslid
Dynasty. The hoards, consisting of coins and ornaments, usually hacked into pieces, appear in the realm of the Piasts for the
first time in the mid-tenth century, and their number gradually
increases until the custom of hoard deposition disappears in the
beginnings of the twelfth century (Jakimowicz 1933;
Kostrzewski 1962). The ornaments from these hoards are covered with granulation, which was a decoration with ancient
traditions (see, e.g. Duczko 1985 Eilbracht 1999; Pliny 1929;
Theophilus 1979; Ogden 1982). Granulation was a favourite
Archaeol Anthropol Sci
ornamentation technique among craftsmen working for social
elites in the first state of the West Slavs, that is, Great Moravia,
in the ninth century AD. The origins of ornaments are to be
searched in the traditions of Late Roman Art which survived in
the Byzantine Empire. Moravian ornaments, which are known
only from burials, are of very high quality and represent a
special phenomenon in early medieval European art (Čáp
et al. 2011; Galuška 2013). After the destruction of the
Moravian state in the early tenth century by the Hungarians,
Moravian goldsmiths moved in two directions: westward to the
Czech state, and eastward to Kievan Rus, created and ruled by
the Scandinavians. Each group of these craftsmen created their
own repertoire of types characteristic only for them. In the
hoards found in the territory of the Piasts, there is a prevalence
of ornaments typical for the Czech art, while ornaments of the
eastern group are known from hoards deposited by the Rus, i.e.
the Scandinavians living in Eastern Europe (Ukraine, Belarus
and the European part of the Russian Federation). In the eastern
hoards, post-Great Moravian ornaments were mixed with typical Norse jewellery, in which the techniques of filigree and
granulation were also employed. Post-Great Moravian ornaments hold a special place in the European history of art, because of their own unique nature. As all jewellery, also those
had religious and social functions (Duczko 2015, 2016, 2018).
A few experimental technological studies were done
(Thouvenin 1971, 1973; Baines 2005) however, they did not
cover physico-chemical properties of jewellery of such type.
Published results of contemporary studies on ornaments made
with the use of granulation and filigree techniques are mainly
focused on gold artefacts (e.g. Scrivano et al. 2013, 2017a, b;
Ontalba Salamanca et al. 1998; Šmit et al. 2000, Šmit and
Šemrov 2006).
A recent study by Ashkenazi et al. (2017, 2018) concerns
results of research on silver treasures whose chronology
strongly precedes the finds discussed in this article. In recent
years, Czech researchers have commenced to fill this gap.
What can be mentioned here is a series of archaeological experiments on the technology of manufacture of early medieval
ornaments from Great Moravia, with a special focus on filigree and granulation (Čáp et al. 2011). Another important
work deals with the composition of metal, construction and
technology of goldsmith decorations discovered at the
BLumbe Garden^ cemetery at Prague Castle (Ottenwelter
et al. 2014). Ornament analyses were carried out by scanning
electron microscopy using X-ray dispersion spectrometry. Yet
another valuable study is a monograph with a detailed discussion on finds from Břeclav - Pohansko VII, including scanning electron microscopy of Great Moravian jewellery from
the Pohansko site (Macháček et al. 2016).
However, the early appearance of Czech ornaments in
Europe did not attract enough attention from researchers. W.
Duczko studied Danish Viking ornaments, including Slavic
artefacts. His first works were published in the 1970s and
1980s (research on finds from Birka in Sweden) and did not
contain detailed analyses of physico-chemical traits of
discussed finds (Duczko 1972, 1984, 1985, 1986). This issue,
on a larger scale, is currently being researched by the authors
as part of two grants in collaboration with the University of
Stockholm and the National Museum in Stockholm.
Material and methods
Archaeological material
This paper discusses the results of research on 26 ornaments
from three early medieval silver hoards discovered in
Słuszków, Rajsków and Stojkowo in Poland (see Fig. 1).
The hoard from Słuszków (Kalisz District, Poland) is one of
the largest ones of such kind in Poland (see Fig. 2). It was
discovered in 1935 during land adjustment. Today, the hoard
is in the collection of the District Museum of the Kalisz Region.
The assemblage contains 13,061 finds, most of which being
cross denars. The latest issues come from the end of the eleventh and the beginning of the twelfth century. The most numerous group in the hoard consists of cross denars of types I, II, IV,
V, VI, VII and VIII. It includes 12,829 items, which is over 98%
of artefacts in the assemblage. In addition, the Słuszków hoard
also contains 32 granulated silver beads decorated with filigree
(25 items with bosses, 4 oval ones and 3 small fragments of
silver sheet with traces of granulation), 7 silver ingots and 71
foreign coins: Arabic, English, Danish, German, Czech and
Hungarian, mostly preserved in fragments. However, the most
spectacular group in the hoard are Palatine Sieciech’s denars:
120 items with a cross pattée and 1 + 2 with a monogram. It is
the largest known assemblage of coins of this magnate.
The second of the examined hoards was accidentally discovered in 1992, when a residential building in the KaliszRajsków quarter was extended (see Fig. 3). Part of the hoard
is kept in the Kalisz Museum and it includes 636 finds with a
total weight of 281.2 g. In this part of the hoard, 146 entirely
preserved oriental coins and their fragments (a fragment of an
Arab-Sasanian drachma from the end of the seventh century,
and dirhams dated to the period between the end of the seventh and the end of the tenth century) were distinguished.
Furthermore, German denars and their fragments, including
the earliest type I cross denars, Czech and Scandinavian coins,
as well as issues of Bolesław Chrobry (type CNP 47) from the
initial period of this ruler’s reign were present in the assemblage. There are 490 fragments of ornaments in the hoard, of
which 16 specimens were selected for archaeometric research.
The third early medieval silver hoard discussed in this paper was discovered in 1926 in a village of Stojkowo (Fig. 4),
10 km to the east of Kołobrzeg (Kolberg) and is deposited
now in the National Museum in Warsaw. Only a part of it
weighting about 740 g has survived, while the rest weighting
Archaeol Anthropol Sci
Fig. 1 Map of finds of the silver hoards discussed in this paper
about 400 g and a covered clay vessel in which the hoard
was buried were lost during the Second World War. The
preserved part consists of 102 coins (chiefly from German
mints and 28 cross denars of types I, II, III, V, VI and
VII), 9 lumps of cast silver or their fragments, 39 fragments of silver bars and silver sheets, 159 fragments of
silver sticks and wire and 152 various silver ornaments
(parts of rings, temple-ring pendants, silver beads, chains,
necklaces and buckles), mostly hacked and broken.
Probably about 400 coins (mostly dirhams) and some other artefacts, among them a few fragments of silver bars,
were lost. Information concerning this lost part of the
hoard was obtained from literature. However, this data is
far from adequate and precise (Kiersnowska and
Kiersnowski 1955).
Structural and elemental composition analyses
Before laboratory analyses, the artefacts were cleaned in
AVEL Silver Cleaner solution (http://www.avel.com/avel-33/
produit/293-silverware-avel-33.html, accessed on 2 August
2017), and then they were bathed in acetone and air dried in
order to remove conservation layers. The conservation of the
jewelleries included mechanical cleaning, application of 5%
disodium edetate solution (Ślesiński 1995) and covering the
surface with Paraloid B-72 acrylic resin (Costa 2001). The
Archaeol Anthropol Sci
Fig. 2 Silver beads from the early
medieval hoard from Słuszków:
West Slavic group. Photo: M.
Osiadacz
state of preservation of the finds was good and no corrosion
was observed.
SEM-EDX (scanning electron microscopy with X-ray microanalysis) was the main technique which was used for the
study of technological changes in surfaces of the discussed
ornaments. This was due to the surface interaction of the excitation electron beam and a possibility of EDX signal registration from near-surface layers (Gójska et al. 2019) in the
region of soldering occurring up to about 30 μm from the
surface (Kolářová et al. 2014). SEM-EDX analysis, described
in detail in Goldstein et al. (2007), is a popular non-destructive
technique used in studies of archaeological finds (e.g.
Scrivano et al. 2017a, b; Ontalba Salamanca et al. 1998;
Ashkenazi et al. 2017, 2018; Linke and Schreiner 2000,
Linke et al. 2003, 2004; Ingo et al. 2004; Miśta et al. 2017;
Gójska and Miśta 2016). Twenty-six artefacts were tested
altogether.
The SEM-EDX study provided information about morphological changes and allowed for a determination of the quantitative elemental composition in the micro-scale, taking specifications of the solder region, base surface and granule compositions into account. The granules and surface where they
were attached by soldering are referred to as the base surface
in the further part of this paper. This was due to their similar
elemental composition. For each technological area of a given
artefact, at least n = 3 measurements were carried out. The
SEM-EDX analysis was done using a Carl Zeiss EVO
MA10 Scanning Electron Microscope equipped with an
EDAX X-Flash Detector 5010 with a 123-eV spectra resolution (Zeiss. Poland; www.zeiss.com) and provided with a
Bruker Quantax 200 Esprit 1.9 system for analyses of EDX
spectra. The image analysis was carried out using a secondary
electron detector (SE) with a resolution up to 2.0 nm. Other
parameters were the following: accelerating voltage 20 keV,
Fig. 3 Silver ornaments from the early medieval hoard from Rajsków: a post-Moravian group; b West Slavic group; c Scandinavian group. Photo: M.
Osiadacz
Archaeol Anthropol Sci
Fig. 4 Silver ornaments from the
early medieval hoard from
Stojkowo: Scandinavian group.
Photo: M. Osiadacz
measurement time 120 s and LLD = 0.1 wt%. The current and
field magnification was adjusted to the type of morphology of
each studied surface. The quantitative analysis was done using
the non-pattern method with an error < 3% for the main elements and < 20% for traces below 1 wt%. Standard reference
materials which were used for EDX result authentication were
Ag and Cu alloy mixtures in all Ag/Cu % range (ESPI metals).
density estimator (KDE) model was used to obtain a 3D model of lead isotopic ratio distribution in artefacts (Kulczycki
2005; Baxter 2003, 2016; Everitt and Hothorn 2011; Everitt
et al. 2011).
Results
Lead isotope analyses
Furthermore, an ore provenance study was carried out based
on the results obtained for 20 ornaments. The micro-invasive
LA-ICP-MS was carried out with an ELAN 9000 Inductively
Coupled Plasma Mass Spectrometer (Perkin Elmer SCIEX,
Canada: www.perkinelmer.com) equipped with an LSX200+ laser ablation system (CETAX, USA: www.cetax.
com). The LSX-200+ combines a stable environmentally
selected 266-nm UV laser (Nd-YAG, solid state, Q-switches)
with a high sampling efficiency, variable 1 to 20 Hz pulse
repetition rate and maximum energy up to 6 mJ/pulse. The
applicability of this technique in archaeological provenance
analyses is briefly discussed by several authors (e.g. Baker
et al. 2006; Budd et al. 1995; Hirata 1996; Stos-Gale & Gale
2009). The NIST 981 reference standard material was used for
quantitative determination of lead isotope concentrations (0.
059042, 0.91464 and 2.1681 for Pb204/206, Pb207/206 and
Pb208/206 with relative standard deviation below 0.1%).
Measured median values (n = 78) with relative standard deviation are 0.0610 ± 1.08, 0.0915 ± 1.02 and 2.1720 ± 1.16% for
Pb204/206, Pb207/206 and Pb208/206, respectively. For each artefact, n = 40 measurements were carried out with SD: < 6% for
Pb206/Pb207, < 7% for Pb208/Pb206 and < 5% for Pb207/204.
The obtained results of the elemental composition and lead
isotope study were processed using principal component analyses (PCA) and linear discriminant analysis (LDA). A kernel
SEM-EDX analysis of technological changes
in the surface of the ornaments
A series of 26 silver ornaments—18 made in filigree and
granulation techniques (in one find from the Rajsków
hoard—the artefact without no. in Fig. 3—the soldering area
was not identified by the SEM-EDX analysis) and 8 without
such decoration (the finds from the Stojkowo hoards, see in
Fig. 4)—were examined. These artefacts belong to the West
Slavic (12 finds—5 from Słuszków, see Fig. 3, and 7 from
Rajsków, see in Fig. 3b), post-Moravian (4 finds from
Rajsków, see Fig. 3a) and Scandinavian (10 finds—2 from
Rajsków, see Fig. 3c, and 8 from Stojkowo, see Fig. 4) groups.
The technological groups were isolated based on visual characterisation according to Duczko (1985).
The surface morphology of all precious metal artefacts was
studied by SEM-SE. In the case of ornaments with granulation, three technological areas were identified: 1—base surface made of silver alloy; 2—joining zone located between the
surface and the decoration; and 3—ornamentation on the base
silver alloy, e.g. granulation and twisted wire.
Furthermore, on the basis of morphological differences in
the ornamentation zone which were identified by SEM observations, three types of joining were found: (i) spilled granulation ornaments, (ii) non-oxidised spherical granules and (iii)
oxidised soldering area with spherical granules.
Archaeol Anthropol Sci
All the analysed beads from Słuszków display similar characteristics of the soldering area with the lack of extensive
oxidised structure in the soldering region. Such structures associated with two different solder types are presented in
Figs. 5 and 6. Figure 5 (surface of find 2 from Fig. 2) offers
examples of SEM-SE images recorded for the first type of the
joining structure. This variety is characterised by granules
which are smoothly embedded in the surface. The size of these
granules is about 300 μm (see Fig. 5). Moreover, the shape of
the granules is fuzzy and a significant merging with the solder
structure can be seen. The ornament is spilled on the surface.
Furthermore, in Fig. 6, one can see granules separated from
the solder layer which is characterised by the lack of extensive
oxide structures. The size of these granules is about 400 μm
(see Fig. 6).
Different technological types of joining areas were observed in the case of ornaments from the Rajsków hoard.
Figures 7 and 8 offer SEM-SE images of a micro-region with
the granulation ornament. Cloudy shapes of joining structures
between granules are visible with the size of the granules from
300 (see Fig. 8) to 400 μm (see Fig. 7).
Based on the SEM images, it can be said that the spilled
ornament (as discussed below) with relatively small size of the
granules and the lack of oxide structures indicates the use of
metallic soldering (Ottenwelter et al. 2014; Macháček et al.
2016; Ferro et al. 2009) in the case of the beads from the
Słuszków hoard. The presence of oxide structure in the area
of tiny granule assemblage in the finds from Rajsków could be
a chemical soldering effect (Čáp et al. 2011; Duczko 1985).
The elemental composition study results confirm the above
assumption, as described below.
Furthermore, the EDX elemental composition of ornaments allowed to distinguish technological micro-areas within
three archaeological types. Ag, Cu, Bi, Pb, Zn, Sn, Au, Hg, Sb
and O concentrations above 0.1 wt% were identified as a
normalised value. The results are presented in Table 1. The
West Slavic and Scandinavian types were divided into two
groups according to visual traits, i.e. beads from Słuszków
have a different soldering area as shown by SEM analyses
(see Figs. 5 and 6). On the other hand, the finds from the
Stojkowo hoard resemble Scandinavian-type artefacts without
granulation (see Fig. 4).
What is important while analysing the results is that the
elemental composition determined for each technological part
is only approximate due to a considerable blur of the elements’
distribution on the surface micro-regions. This results from the
fact that these ornaments were processed at high temperatures
(Untracht 1985; Wolters 1983). In our study, the division into
the base surface and the soldering area was confirmed by the
linear discriminant analysis. Table 2 presents the results of
LDA correct allocation for two selected (based on elemental
composition in Table 1) technological areas. The greatest spill
of solder over the surface is visible in the WSS type. Based on
the results presented in Table 2, the division shown in Table 1
seems to be appropriate.
As it can be seen in Table 1, the soldering area of the West
Slavic artefacts from Rajsków is the most oxidised (O up to
51.4 wt%) with the highest concentration of copper (Cu) up to
57.3 wt% and high tin (Sn) and antimony (Sb) contents. The
solder in the post-Moravian jewelleries (see Figs. 7 and 8) is
similar with regard to the content of O, while it has a lower Cu
content (up to 27.8%) and slightly higher Sn (up to 24.7 wt%),
Pb (up to 7.0 wt%) and Sb (up to 19.5 wt%) concentrations.
Concerning the solder type, all five beads from Słuszków
are characterised by the lack of very oxidised structure (see
Figs. 5 and 6) with the O content in the range from 3.3 to
22.6 wt%. The Cu, Sn and Zn contents are also low, as compared with other types of jewelleries (see Table 1) with slight
Pb and Cu enrichment.
The soldering area of the Scandinavian jewelleries from
Rajsków is enriched in Cu, Sn, Sb, Pb and O with regard to
their base surface. The base surface of the finds without granulation from the Stojkowo hoard is different from other types
of the base surface (see Fig. 9a). It is enriched in Cu and Pb.
Generally, the elemental composition differences determined
for all the types of jewelleries are presented graphically below,
both as a difference in the content of elements in the soldering
areas (see Fig. 9b) and raw silver (see Fig. 9a) which was used to
produce the base surface and ornaments. In the diagrams below,
all EDX measurements were taken into account.
Fig. 5 SEM-SE images of the surface of the silver bead from Słuszków (Fig. 2: no. 2) characterised by spilled granulation ornament. The technological
parts are as follows: 1—base surface, 2—soldering area and 3—granules as part of the granulation ornament
Archaeol Anthropol Sci
Fig. 6 SEM-SE images of the surface of the silver bead from the Słuszków hoard (Fig. 2: no. 3), find 12683. Regular spherical granules without
extensive oxidised solder area can be seen. Designations (1–3) as in Fig. 5
Figure 9 shows the results of the elemental composition
analysis presented as a LDA diagram (Baxter 2016, 2003;
Everitt and Hothorn 2011). The LDA confusion matrix can
be found in Table 3.
As it can be seen in Fig. 9 and Table 3, the base surface
regions in all types of jewelleries with granulations are similar
concerning their elemental composition. A better separation
(61%) is observed for the artefacts without granulations from
the Stojkowo hoard. Furthermore, in the case of the soldering
area, a better allocation to the group can be seen for WSS
(72%), WSR (54%) and Sc.R (50%). The soldering regions
of PM jewelleries are similar to all other types and the allocation to the predicted group is 30%. Figures 10, 12, 14 and 15
illustrate a graphical distribution of variability of Ag, Cu, Bi,
Au, Pb, Hg, Sn, Zn, Sb and O concentrations. In the diagrams,
there are marked areas (respectively, I–II, a–c) with composition anomaly in the groups in question. Figures 10b, 12b, 14b
and 15b (as a fragment of Fig. 9b) present LDA separation of
the soldering area for each artefact within archaeological
groups. Numerical designations of the finds are explained in
Figs. 2 and 3. Moreover, the a) parts of Figs. 10, 12, 14 and 15
contain PCA correlation-type diagrams presenting the results
of the elemental composition analyses of the soldering region
and the base surface in each technological group.
Generally, as it is shown in the PCA diagrams from panels
a of Figs. 10, 12, 14 and 15, the division into the base surface
and the soldering region within a given archaeological group
based on the elemental composition is justified (which is in
accordance with what is offered in Table 2). The main classification error occurs only in Fig. 15: point II. In all PCA
diagrams, the Ag content is correlated with the base surface,
while Cu, Sn, Zn, Sb and Bi are related to the soldering region.
However, as reported by Kolářová et al. (2014), the registered
EDX signal gives information about the base surface contaminated by solder components (Wolters 1983).
In Fig. 10, in the soldering area, there are two notable
anomalies with higher Cu (up to 29.5 wt%), Sn (up to
8.8 wt%), Sb (up to 4.6 wt%) and O (up to 56.5 wt%) contents.
They concern find no. 2 in Fig. 3c. The SEM-SE images of the
soldering region of this pendant can be seen in Fig. 11. In turn,
the composition of this joining area is slightly similar to what
occurs in the WSR and PM type (see Fig. 9b).
The largest anomalies within the soldering area are present
in the PM group, which is also evidenced by the LDA results
presented in Table 3 (only 30% of correct allocations). There
are observed anomalies in the concentration of low-melted
elements such Pb, Sn, Zn, Sb, Bi and Cu. These anomalies
can be seen in the case of finds nos. 2 (no a, b, I in Fig. 12) and
4 (no c, II, III in Fig. 12) from Fig. 3a. The first one is
characterised by a much higher content of Sb (up to
19.5 wt%), Sn (up to 24. 7 wt%) and Cu (up to 27.8 wt%)
with higher Pb, Zn and O concentrations. The other one is
characterised by the oxidised soldering region (up to
50.4 wt%) with higher Cu and Sn concentrations, as it can
be seen in Fig. 7. In the PCA diagram (Fig. 12a), there are
strong Sn–Sb and Zn–Cu correlations, which means that these
Fig. 7 SEM-SE images of the surface of the silver bead from the Rajsków hoard (see Fig. 2: no. 4). An oxidised solder area and regular spherical granules
can be seen. Designations (1–3) as in Fig. 5
Archaeol Anthropol Sci
Fig. 8 SEM-SE images of the granulation area of the silver bead surface from the Rajsków hoard (see Fig. 2: no. 1). There are oxidised soldering
structures (2) located in the space between granules (3)
components could be added in this substrate correlation to the
joining mixture. Figure 13 shows the soldering region of the
abovementioned pendant marked as no. 2 in Fig. 3a.
The raspberry pendant presented below is an example of an
ornament characterised by higher contents of low-melted elements in the oxidised solder areas. Moreover, a higher percentage of gold (Au) up to 2.7 wt% and mercury (Hg) up to
2.4 wt% was recorded in the entire artefact. Generally, for the
entire assemblage from the Rajsków hoard, the mercury enrichment (up to 4.0 wt%) is mainly observed for the base
surface, but in some cases, it is also related to the soldering
region. For five ornament fragments—a bead with a bump,
WS type (see Fig. 3b: no. 2, see Fig. 14 below point I); a starry
Table 1
earring with filigree (Fig. 3b: no. 6, WS type); an earring (PM
type); a round pendant (Sc type); and a raspberry pendant (PM
type)—a slightly increased content of gold and mercury was
detected in the micro-region.
The soldering region of the WSR group is characterised by
54% allocation to the correct group with a high (31%) allocation to the PM group (see Table 3). The two anomalies are
observed for two artefacts: nos. 2 (see point I in Fig. 14) and 3
(see point a in Fig. 14) from Fig. 3b. Generally, the entire
soldering area of the WSR group is oxidised and characterised
by the positively correlated Sn, Cu and Sb contents, while in
the PM group there is the oxidised soldering area with correlated Cu–Zn and Sb–Sn contents (see Fig. 12). Moreover, the
SEM-EDX analysis results
Arch. type
West Slavic
Hoard
(wt%)
Ag
Cu
Bi
Au
Pb
Hg
Av. (n = 37)
Δ
Soldering area Av. (n = 21)
Δ
Base surface Av. (n = 42)
Δ
Soldering area Av. (n = 26)
Δ
Base surface Av. (n = 41)
87.8
72.6–95.6
79.5
63.1–88.7
88.8
69.3–95.7
33.4
2.2–87.6
87.9
3.4
< 9.5
6.7
2.4–11.0
3.9
2.3–9.4
23.0
3.4–57.3
3.2
0.7
< 3.4
1.3
< 5.0
0.4
< 3.0
1.0
< 9.5
0.9
0.7
< 4.7
0.9
< 4.2
0.6
< 3.4
0.7
< 6.2
1.0
0.7
< 3.4
1.7
< 6.3
0.5
< 3.5
1.0
< 6.6
0.3
0.7
0.1
< 3.1 < 1.1
0.9
0.3
< 2.8 < 1.7
0.5
0.3
< 2.8 < 2.1
0.6
3.9
< 3.8 < 18.6
1.1
0.1
Δ
Soldering area Av. (n = 30)
Δ
Base surface Av. (n = 8)
Δ
Soldering area Av. (n = 9)
Δ
Base surface Av. (n = 31)
75.8–99.0
50.6
4.9–75.7
90.2
83.4–96.3
58.3
5.0–80.1
84.9
0.5–6.0
12.7
4.4–27.8
3.2
1.4–6.1
11.8
4.6–29.5
6.0
< 4.0
1.1
< 5.4
0.2
< 1.5
0.6
< 3.5
1.2
< 3.2
1.2
< 3.1
0.6
< 3.4
1.5
< 4.9
0.8
< 2.8
1.7
< 7.0
0.3
< 1.6
1.6
< 4.8
1.4
< 4.0 < 1.4 < 0.7 < 0.1 < 18.4
0.9
4.9
0.5
2.3 24.2
< 3.4 < 24.7 < 2.3 < 19.5 9.3–50.4
1.1
0.2
0.1 < 0.1 4.2
< 2.2 < 0.7 < 0.6 < 0.1 1.4–7.7
1.2
2.8
0.2
1.1 20.9
< 2.7 < 8.8 < 1.1 < 4.6 8.3–56.5
0.7 < 0.1
0.4 < 0.1 4.6
Słuszków (WSS), Base surface
5 obj.
Rajsków (WSR),
7 obj.
Post-Moravian Rajsków, (PM),
4 obj.
Scandinavian
Tech. area
Rajsków
(Sc. R), 2 obj.
Stojkowo
(Sc. St), 7 obj.
Δ
60.6–92.2 2.8–17.3 < 3.1 < 2.3 < 3.5 < 2.7
n number of measurements, Δ range of composition variation for the technological area
Sn
Zn
Sb
0.1 < 0.1
< 1.0 < 0.1
0.2
0.1
< 0.9 < 0.9
< 0.1 < 0.1
< 0.1 < 0.1
0.5
2.2
< 2.3 < 13.1
0.1 < 0.1
< 0.6 < 1.3
O
6.0
1.2–16.0
8.5
3.3–22.6
4.8
< 20.7
33.7
4.3–51.4
5.6
< 0.1 0.7–21.2
Archaeol Anthropol Sci
Table 2 Part of the LDA confusion matrix for the training sample
showing correct allocation for the technological areas of the
archaeological types (two training sets/technological group—base surface and soldering area; 10 variables: Ag, Cu, Bi, Au, Pb, Hg, Sn, Zn,
Sb, O)
Table 3 LDA confusion matrix for the training sample. Data obtained
for the base surface and the soldering area of jewelleries groups
Correct allocation: n (%)
Base surface (as in Fig. 9a)
Sc.R
2 (25%)
2 (25%)
Sc.St
2 (7%)
19 (61%)
PM
10 (24%)
0 (0%)
WSS
2 (6%)
5 (14%)
WSR
10 (24%)
5 (12%)
Soldering area (as in Fig. 9b)
Sc.R
5 (50%)
–
PM
7 (23%)
–
Base surface
Soldering area
Sc.R
6 (75%)
10 (100%)
PM
WSS
WSR
41 (100%)
28 (80%)
42 (100%)
25 (83%)
14 (67%)
22 (85%)
WSS soldering region demonstrates a better Pb–Zn
correlation.
The soldering region of the WSS group is in 71% of cases
allocated to the correct group. Only six measurement points
are better assigned to other groups (see Table 3). This group is
best distinguished in terms of the solder composition (see Fig.
9b). However, the distinction between base and soldering is
the most disturbed (as shown in Table 2 and Fig. 15a), which
is an effect of spilling of the solder over the surface (Wolters
1983). In Fig. 15, there are four protruding points in the group
with different compositions. These compositions are related to
two artefacts. Generally, in the WSS group, the soldering region demonstrates slight Pb and Cu enrichments with a lower
oxidisation degree (Table 1, Figs. 5 and 6).
Lead isotopic characteristics of the provenance of raw
silver
One of the most important questions concerning the investigated silver ornaments is the provenance of the raw material. It
From/to
n (%)
WSS
WSR
Sc.R
3 (14%)
1 (4%)
Sc.St
–
–
PM
WSS
WSR
2 (25%)
3 (10%)
13 (32%)
8 (22%)
5 (12%)
0 (0%)
2 (6%)
10 (25%)
12 (33%)
9 (21%)
2 (25%)
5 (16%)
8 (19%)
9 (25%)
13 (31%)
0 (0%)
9 (30%)
3 (30%)
6 (20%)
2 (20%)
8 (27%)
2 (9%)
8 (31%)
15 (72%)
3 (11%)
1 (5%)
13 (54%)
n number of measurements
is important to know whether the silver comes from one or
many different sources. It may be supposed that re-melting of
earlier artefacts took place in Europe since the Migration
Period (400–800 AD). Therefore, one can expect more than
one value of individual isotopic ratios in one and the same
artefact. Due to this, destructive analytical techniques, such
as TIMS or ICP-MS (e.g. Cattin et al. 2009; Ettler et al.
2015), may introduce a considerable error to the interpretation
of results. This is because these techniques yield an average
result already in the course of sampling. In this paper, it is
attempted at providing results of isotopic analyses taking into
consideration changes of the so-called isotopic signature of
the sample in the micro-scale. These changes may result from
possible re-melting or heterogeneity of the raw material which
Fig. 9 LDA showing the variability of a Ag, Cu, Bi, Au, Pb, Hg and O contents in the base surface of the archaeological types and b Ag, Cu, Bi, Au, Pb,
Hg, Sn, Zn, Sb and O contents in the soldering area of the finds with granulations within archaeological types. Designations of the groups as in Table 1
Archaeol Anthropol Sci
Fig. 10 Scandinavian-type finds with wires from the Rajsków hoard presented in Fig. 3c as nos. 1 and 2 (Sc.R type): a PCA results for the base surface
and the soldering area and b LDA results for the soldering area of individual finds from the group (zoom of Fig. 9b)
was used. The isotopic analysis which is offered below was
divided into two areas—an analysis within technological
groups and a provenance analysis. In the latter case, geological data (as means) was taken from the available literature
(Ettler et al. 2015; Merkel et al. 2013; Hatz et al. 1991). In
both cases, all LA-ICP-MS results were taken into consideration for the artefacts. Furthermore, linear discriminant analysis was applied to search for differences between groups for
the following values: Pb206/Pb207, Pb207/Pb204 and Pb208/
Pb206, as well as Pb206/Pb207 and Pb208/Pb206 in the case of
the provenance analysis.
Moreover, a KDE model (Baxter 2003, 2016) proved useful, as it allows to create a continuous function describing the
probability distribution of the lead isotopic ratios being an
effect of the heterogeneity of metal in the examined artefacts.
An example of such a model is presented in Fig. 16.
Having analysed lead isotopic ratios presented as
scatterplots and using the kernel density estimation of these
ratios, one can draw conclusions about the provenance of
silver in the sample. If the values of lead isotopic ratios change
in one direction continuously from point to point, which is
visible as a significant peak width, or the kernel function has
several local maximums (see Fig. 16), one can suspect that the
silver was re-melted (Merkel 2016; Eniosova 2009; Eniosova
and Mitoyan 2011). Such a situation has been observed in all
the studied artefacts.
Figure 17 and Table 4 (see also the Electronic supplement,
2. Linear Discriminant Analysis – Ornaments) offer an LDA
lead isotope ratio distribution in four technological groups.
The analysis demonstrates that the raw material is similar with
regard to its isotopic ratios in almost all the examined groups.
Data obtained from the LDA confusion matrix demonstrates
that the highest lead isotope homogeneity can be seen in the
case of the West Slavic ornaments from Rajsków (WSR)
(89% correct classifications). The percentage of correct classifications is much lower for post-Moravian ornaments (merely 35%), while no correct classification was obtained for
Scandinavian ornaments and West Slavic ones from
Słuszków.
The LDA (Fig. 18, see also the Electronic supplement, 5.
Linear Discriminant Analysis—Provenance, Confusion matrix for the training sample) of the geological data
Fig. 11 Round pendant (Fig. 3c, no. 2) from the Rajsków hoard, Scandinavian type—general view and SEM-SE images of the soldering region
Archaeol Anthropol Sci
Fig. 12 Post-Moravian–type finds with granulations from the Rajsków hoard presented in Fig. 3a as nos. 1–4 (PM type): a PCA results for the base
surface and the soldering area and b LDA results for the soldering area of individual artefacts from this group (zoom of Fig. 9b)
demonstrates a strong similarity between ores. Out of 17 deposits, a reasonable percentage of correct classifications was
obtained in four cases only. The following deposits are clearly
different from others: Afghanistan, Freiberg (Germany) and
the Tatro-veporit unit (Slovakia)—100% of correct classifications. There is also a good isolation for Uzbekistan (76% of
correct classifications). The assemblages of Rammelsberg
(Germany), Gammersham (Germany) and Neo-volcanic deposits are classified into the Tatro-veporit unit in 100% of
cases. The isotopic composition of samples from the Polish
deposits of Olkusz–Chrzanów–Pomorzany (marked as
OlkChPom) and the Slovak deposit of Gemer is also similar
to the Slovak Tatro-veporit deposits.
This rather poor separation of deposits on the basis of Pb
isotopic ratios strongly influences the results of provenancing
attempts. Results of 701 analyses on the discussed artefacts
were processed by LDA, but in most cases (see Electronic
supplement, 5. Linear Discriminant Analysis—Provenance,
Results for the prediction sample), no clear attribution to any
deposit was achieved. It was conservatively assumed that a
classification could be considered reliable when the prediction
of probability was at least 70%. Thus, only in 250 cases (that
is, 36%), a more or less unambiguous classification was
obtained. Not surprisingly, the metal in the artefacts was mostly attributed to those deposits which were clearly different
than others.
Furthermore, these results demonstrate that the metal in a
given artefact may be of different origin (see Electronic supplement, 5. Linear Discriminant Analysis—Provenance,
Results for the prediction sample). This supports the assumption of re-cycling and re-melting of raw material from various
sources.
As it can be seen in Table 5 (see also the Electronic supplement, 5. Linear Discriminant Analysis—Provenance,
Results for the prediction sample, and 6. Summaric results
for provenance), the isotopic composition in individual groups
results from the fact of mixing of the raw material from
Central Asian (Afghanistan and Uzbekistan), German
(Freiberg) and Polish ores. Interesting conclusions can be
drawn from the analysis of individual groups. In all Slavic
groups (that is, both West Slavic and post-Moravian), there
is a preponderance of Freiberg silver over that from
Uzbekistan and Afghanistan (if considered separately).
However, it seems that in total the Asian raw material still
played the most important role (Merkel 2016; Eniosova
2009). There are also some differences between groups of
Fig. 13 Raspberry pendant (Fig. 3a, no. 2) from the Rajsków hoard, post-Moravian type—general view and SEM-SE images of the soldering region
Archaeol Anthropol Sci
Fig. 14 West Slavic–type finds with granulations from the Rajsków hoard presented in Fig. 3b as nos. 1–6 (WSR type): a PCA results for the base
surface and the soldering area and b LDA results for the soldering area of individual finds from the group (zoom of Fig. 9b)
Slavic jewellery concerning the share of individual deposits.
What is most striking, however, is a very different proportion
of metal from various sources in Scandinavian jewellery. The
share of European deposits is 32%, while nearly 70% of metal
seems to have come from Asian sources. Of course, these
observations must be treated with care. First of all, the number
of the examined artefacts was not very high, which may pose
problems for the statistical representativeness of results.
Furthermore, the aforementioned rather poor separation between individual deposits must be taken into consideration.
Last, but not least, a problem of missing sources must be borne
in mind. That is, the LDA-based statistical processing of data
will classify given observations only to those deposits which
are present in the assemblage. Silver which was used in the
discussed artefacts could also come from other deposits,
whose isotopic composition may be similar to those which
were included into the analysis.
Discussion
Jewelleries craft
A significant part of the investigated jewellery from the
Rajsków and Słuszków hoards is granulated. The results show
that these elements are permanently bonded to the substrate by
the process based on the use of copper compounds (Kolářová
et al. 2014). The properties of solder based on Ag–Cu are
widely described in Nature (Ashkenazi et al. 2017).
Intentional doping of silver with copper up to 2.6 wt%
Fig. 15 West Slavic–type finds with granulations from the Słuszków hoard presented in Fig. 2 as nos. 1–5 (WSS type): a PCA results for the base surface
and the soldering area and b LDA results for the soldering area of individual artefacts from the group (zoom of Fig. 9b)
Archaeol Anthropol Sci
Fig. 16 KDE calculated (surface plot of a scatterplot) for lead isotope ratios Pb207/206 and Pb208/206 for two artefacts from the Rajsków hoard as an
example of re-melted samples
(Ashkenazi et al. 2017) causes the melting point of Ag–Cu
alloy to be lower than 961 °C for pure Ag (Tuah-Poku et al.
1988; Bastow 2013). From an old handbook (twelfth century
receipts of Theophilus Presbyter; Pliny 1929; Leyden Papyrus
X), two types of soldering—metallic and non-metallic
(chemical)—are known. These were discussed in detail by
Duczko (1985, p. 26–28).
Metallic solders known from the third century BC are mixtures of two or three metals (Wolters 1978, p. 5; 1983, p. 62).
While silver artefacts are soldered, the main component is Ag,
while other additions could be gold, brass or tin (Wolters
1978, 1983, p. 61ff). The obtained soldering effect is not artistically convincing. The solder mixture covers the entire surface between the ornaments and the base surface (Carrol 1974,
p. 35; Kolářová et al. 2014). The use of metallic soldering is
particularly advantageous when joining larger and more durable jewellery items. However, using metal solder for
Fig. 17 LDA showing Pb 206 /Pb207 , Pb207 /Pb204 and Pb208 /Pb206
variability in four groups of ornaments
decoration is more problematic for filigree jewellery and granulation. When melted, the solder is not absorbed into the surface and forms a Bpuddle^ in which small decorative elements
melt (Eilbracht 1999). This type of soldering has been identified by Macháček et al. (2016) during their study of the Great
Moravian jewellery and on the ornaments from the BLumbe
Garden^ cemetery at Prague Castle (Ottenwelter et al. 2014, p.
283). In line with what was said above, the spilled granulation
(see Figs. 5 and 6) with higher contents of Pb and Cu (added
as a joining Ag-based mixture) in the soldering area (Table 1)
is characteristic for the beads from Słuszków hoard. The beads
are remarkable for their relatively ungrouped granules, so the
assumption concerning the application of metallic soldering is
justified. The granules are tiny (300–400 μm) and the solder is
spilled over all the surface (see LDA: Table 3, Fig. 10a). Apart
from that, the shape between granules which are close to each
other is fuzzy (see Fig. 5). The WSS group soldering area is
strongly different from that in the remaining jewellery under
study (Fig. 9b, Table 3).
The remaining part of the examined jewellery with granulation and filigree from Rajsków (post-Moravian and West
Slavic types) and Stojkowo (Scandinavian type) demonstrates
traces of use of the non-metallic (chemical, bonding) soldering. Non-metallic solders consist either of mineral or artificially produced copper compounds (Duczko 1985). Written
sources described a few such substances: malachite (in antiquity called chrysocolla) and azurite, naturally occurring forms
of basic copper carbonate; patina (i.e. a copper alloy resembling enamel covering old bronze artefacts—mostly copper
carbonate, containing natural oxides and oxides of bronze
additives—tin, lead, zinc, arsenic); verdigris, a mixture of basic copper acetate and copper acetate pentahydrate, produced
by the action of vinegar on copper; and Roman vitriol, cupric
sulphate pentahydrate (Tamla 2016). In order to prepare a
diffusion agent, a copper compound is added to a mixture of
Archaeol Anthropol Sci
Table 4 LDA confusion matrix
for the training sample. Data
obtained for lead isotope ratios:
Pb206/Pb207, Pb207/Pb204 and
Pb208/Pb206 in the jewelleries’
groups
From/to
PM
Sc.R
WSR
WSS
Total
% correct
58 (35%)
5 (7%)
32 (11%)
25 (15%)
0 (0%)
0 (0%)
0 (0%)
0 (0%)
107 (65%)
65 (93%)
266 (89%)
142 (85%)
0 (0%)
0 (0%)
0 (0%)
0 (0%)
165 (100%)
70 (100%)
298 (100%)
167 (100%)
35
0
89
0
n (%)
PM
Sc.R
WSR
WSS
n number of measurements
Fig. 18 LDA showing Pb206/
Pb207 and Pb208/Pb206 variability
for geological data (means) obtained from the literature
Archaeol Anthropol Sci
Table 5 Results of LDA ore
provenance classification for four
jewelleries’ groups
WSS
WSR
PM
Sc.R.
Total
Number of
analyses
Prediction
Freiberg
Prediction
Uzbekistan
Prediction
Afghanistan
Prediction
OlkuszChPom
Prediction
Gammersham
68
90
73
19
250
25 (37%)
27 (30%)
28 (38%)
5 (26%)
85 (34%)
18 (26%)
31 (34%)
22 (30%)
10 (53%)
81 (32%)
18 (26%)
22 (24%)
14 (19%)
3 (16%)
57 (23%)
6 (9%)
10 (11%)
9 (12%)
1 (5%)
26 (10%)
1 (1%)
0 (0%)
0 (0%)
0 (0%)
1 (0%)
an organic adhesive (e.g. gum tragacanth, gum acacia, fishglue) and water. Sometimes, such mixture is enriched by socalled asem described by Leyden Papirus X (Demortier et al.
1999). The nature of asem is unknown, but this term is used in
an old handbook with reference to a substance whose properties are similar to precious metals (Berthelot 1889). With this
solution, the decorative elements are fastened to the substrate,
and the artefact is then heated (Wolters 1983).
In reference to what was said above, the granulation and
wire-ornamented West Slavic (WSR), post-Moravian type
(PM) and Scandinavian finds from the Rajsków hoard show
Cu, Sn and Sb (see Table 1) enrichments with a higher oxidation degree in the soldering area (see Figs. 7, 8, 11 and 13).
The content of Cu (which is a melting agent) is up to
57.3 wt%. This gives a melting temperature over 779 °C (a
lower value occurs for 28.1 wt% Cu) (Ashkenazi et al. 2017).
The soldering regions of all three archaeological types from
the Rajsków hoard are similar (see Fig. 9b, Table 3). These are
characterised by a good separation from the base surface (see
Tables 1 and 2). Furthermore, the bonding area with a higher
content of copper (Cu) is enriched in low-melting elements
(Sn, Sb, Zn; Baxter 2003). These were presumably intentionally added to the alloy as asem in diffusion bonding or as part
of a Cu-based mixture. The oxidation of the soldering region
is correlated with the presence of Cu and Zn in postMoravian–type artefacts (see Fig. 12a), with the presence of
Sb, Cu and Sn in West Slavic finds (see Fig. 14a) and with the
enrichment in Sb and Sn in Scandinavian finds (see Fig. 15a).
Generally, the presence of the oxide structure in the joining
region, around the granules and wires, could result from
enough reducing atmosphere during the chemical soldering
or could be an effect of improper heat treatment. If soldering
is to be successful, it is essential for the metal surfaces to be
absolutely clean. This is because a series of thermal treatment
reactions occurs during this process: at 100 °C, CuO is formed
from Cu compounds; at 600 °C, the reducing atmosphere is
created by glue carbonising; and at 850 °C, Cu oxides are
reduced to Cu by CO (Duczko 1985, p. 25). Heating above
900 °C causes the metallic copper to diffuse to the base surface and to the alloy of ornaments (Wolters 1983, p. 57).
Charcoal fuel was used as a temperature agent. It has certain
properties which render it particularly suitable for soldering
operations. It generates high temperatures necessary for the
processing of gold, silver and copper. Burning charcoal maintains a temperature of 800 °C without an artificial air supply.
The temperature increases to 1300 °C when air is supplied
through a single pair of bellows or a blow-pipe (tools primarily required for minor soldering operations). If there is a continuous blast from water-powered double bellows, the temperature rises as high as 1650 °C (Untracht 1985). The other
property of charcoal is the ability to create a reducing atmosphere, which protects the heated metal from oxygen in the air.
This is important due to the presence of copper and other
easily oxidising elements (such as zinc, tin, antimony in our
cases) in solder alloys. When heated, those elements produce
oxides, which coat the surface of the artefacts, thus preventing
the completion of the soldering process, which is visible in
Figs. 7, 8, 11 and 13. If charcoal fire is not sufficient to
completely eliminate oxidisation, it is necessary to use a special anti-oxidisation agent, called flux which coated all the
joints. The following substances could be used as flux: soda
(sodium bicarbonate NaHCO3), tartar (potassium bitartrate
KC4H5O6), alum (hydrated potassium aluminium sulphate
Kal(SO4)2∙12H2O), potash (potassium carbonate K2CO3)
and the most important factor, that is, borax (sodium
tetraborate Na2B4O7). All these substances are well documented in historical sources (Wolters 1978).
Furthermore, the presence of Zn and Sb in the joining mixture can be associated with the use of such minerals as
tetrahedrite ([Cu,Fe]12Sb4S13) (Munoz et al. 2015), which is
also a source of copper, and sphalerite (ZnS). The latter is
often found with Ag-rich galena deposits (PbS) which were
the main source of silver in medieval Poland and Europe (Gale
and Stos-Gale 2000; Chamberlain and Gale 1980).
Furthermore, antimony is associated with freibergite mineral
[Ag 6 (Cu 4 Fe 2 )Sb 4 S 13–x ] which characterised Freiberg
(Germany) silver ores based on galena and sphalerite boards.
Antimony-rich deposits were also located in Poland in Lower
Silesia, e.g. in Dębowiny in the Beskidy Mountains between
Srebrna Góra and Złoty Potok (Mączka and Stysz 2008). In
the Early Middle Ages, silver was extracted in this region by a
refining process called cupellation. The aforementioned minerals which may have been a source of elements used to produce soldering mixture could be added as asem part to resin
glue being a binder in non-metallic soldering. Moreover, with
regard to the antimony content, we may assume that our
Archaeol Anthropol Sci
ornaments were made of silver from cupellation directly associated with this element. An important thing in the cupellation
process is wasting of silver by evaporation and dissolution of
silver in lead oxide (PbO) and later soaking into a cupel (alkaline—for example from animal bone bound with potash).
An optimal amount of lead must be selected—and this already
shows the quality of the workshop (the same as the temperature of the furnace, the amount of copper admixture and the
quality of the cupel itself). Also, a significant influence on
silver wasting is exercised by the addition of antimony and
tellurium which facilitate silver infiltration into the cupel. If
the addition of these elements actually took place in order to
produce raw silver of the studied jewelleries, antimony would
be present in the entire artefact and not only in the solder
region.
From BDe Re Metallica^ of Agricola (the work is of a
sixteenth century date, but it also discusses much earlier technologies), we learn that the stibium mineral (probably
antimonite or other antimony minerals) was used, among
others, for the metallurgical process of recovering gold from
pyrite. Excepting reduction with silver, and separation with
nitric acid and a method of reduction with lead and silver,
followed by cupellation and parting with nitric acid is the third
method that can be isolated. Yet another method is the reduction with lead or antimony, followed by cupellation. The use
of sulphur or antimony sulphide would tend to part out a
certain amount of silver and thus to obtain fairly pure bullion
upon cupellation.
Silver was also parted from gold by means of stibium. The
use of antimony sulphide to part silver from gold is based
upon a greater affinity of silver than antimony to sulphur.
Thus, the silver, as in other processes, is converted into a
sulphide and is absorbed in the regulus, while the metallic
antimony alloys with the gold and settles on the bottom of
the pot. This process has several advantages over the
sulphurisation with crude sulphur; antimony is a more convenient vehicle of sulphur, for it saves the preliminary
sulphurisation with its attendant difficulties of volatilisation
of the sulphur; it also saves the granulation necessary in the
former method; eventually, the treatment of the subsequent
products is simpler.
The process in this description can be divided into six operations: (a) sulphurisation of the silver by melting it with
antimony sulphide; (b) separation of the gold Blump^
(massula) by jogging; (c) re-melting the regulus (mistura)
three or four times for a recovery of further Blumps^; (d) remelting of the Blump^ four times, with further additions of
antimony sulphide; (e) cupellation of the regulus in order to
recover the silver; and (f) cupellation of the antimony from the
Blump^ to recover the gold (Agricola 1912, p. 451).
The method described by Agricola for treating antimony
sulphide was still in use in the twentieth century in the Harz, in
Bohemia and elsewhere. The stibnite was liquated out at a low
heat and then it dripped from the upper to the lower pot. The
resulting purified antimony sulphide is the modern commercial Bcrude antimony^ or Bgrey antimony^ (Agricola 1912, p.
428).
In the case of mercury content in all studied artefacts, this
element was widely used in workshops working with precious
metals, especially gold. Vitruvius in his work BOn architecture
...^ (Agricola 1912, p. 123) said: BMercury is suitable for
many purposes. Without it, you can not gild either silver or
bronze [...] mercury attracts all gold particles and connects
with it.^ Theophilus (1979) in his recipes recommends it,
among others, as an additive for grinding gold or silver (five
parts of mercury and six parts of silver), for obtaining the socalled sand (extracted from the sand mined on the banks of the
Rhine) or as an alloy for casting tin vessels (one quarter pound
of tin for one pound of tin) and final polishing of these castings
(a mixture of dissolved tin chips in mercury). Therefore, the
presence of gold and mercury in the results of research on the
ornaments is probably not intentional (traces after amalgam
gilding) but results from contamination, for example, with
components of a solder or alloy intended for granulation.
Assessing provenance
When analysing the origin of the raw material, it should be
remembered that metal artefacts are not geological ores. The
objects are created by a series of anthropogenic actions, such
as extraction of raw metal, re-cycling or alloying with other
metal. These actions cause the artefact’s structure to be heterogeneous in the micro-scale. This is reflected in the heterogeneity of the chemical composition–elemental and isotopic
character of the artefact (Liu et al. 2018). Therefore, the measured composition is merely a resultant of an average of the
composition. For this reason, the interpretation of the obtained
results may be burdened with an error, and it should be treated
as a subject for further verification. Furthermore, it could be
suggested that apart from Pb, other isotopic ratios may also be
of use, for example Cu and Ag (Desaulty et al. 2011). Quite
promising results have recently been obtained in iron provenance studies which employed Os isotopic signatures
(Dillmann et al. 2017, with further reading).
Three phases of silver inflow are isolated for Poland in the
Early Middle Ages (tenth to twelfth century). In the first phase
which falls within the pre-state period (to the end of the tenth
century), there is a preponderance of oriental silver, chiefly
Arab dirhams (Burâkov 1965, 1974; Bubnova 1963; Cowell
and Lowick 1988; Dekówna 1971, p. 496, 487; Merkel 2016;
Eniosova 2009; Eniosova and Mitoyan 2011). For about
250 years (since the eighth to the mid-tenth century), dirhams
are the main component of hoards found in Poland. This
changes in the second half of the tenth century, when
Western European coins and then local issues commence to
prevail. This second wave of inflow (second half of the tenth
Archaeol Anthropol Sci
to late eleventh century) was related to a dominant role of
coins which were coming to Poland from Western European
countries, chiefly from Germany, where enormous deposits of
silver were discovered in the Harz in the Rammelsberg mine
in the third quarter of the tenth century (Jammer 1952, p. 62;
Suchodolski 1971, p. 22). The third phase is related to the use
of native silver and is well visible in finds since the rule of
Bolesław Krzywousty (1107–1138).
Due to the technological nature of the artefacts, i.e. their
heat treatment and a considerable blur of intentionally added
layers, there seems to be little point in attempting at
interpreting the elemental composition in relation to the composition of individual geological deposits. More so, because
the discussed silver deposits are PbS and ZnS systems with
similar additives. What is remarkable is the aforementioned
presence of Sb in the deposits from Freiberg and from Lower
Silesia. The percentage share of individual elements in the
artefacts does not reflect the initial composition of the deposit,
which was first extracted from the ore. Then, the obtained raw
material was melted and intentional additives were added in
order to receive the desired technological parameters.
The results of the Pb isotope ratio study provide grounds
for concluding that the silver used to produce the discussed
early medieval artefacts comes from different sources and ores
(Table 5). This means that the investigated ornaments may
have been made of silver coming from various other artefacts
and ores. The results of our investigations may suggest the
silver used for manufacturing the discussed jewellery chiefly
originated from Asia (Uzbekistan and Afghanistan) or
Freiberg in Germany.
However, at present, it is difficult to compare all previously
published studies (Gójska et al. 2019)—most of the performed
analyses were obtained by X-ray fluorescence spectrometry
(XRF) or X-ray microanalysis spectrometry (EDX) on surfaces (often corroded or contaminated), which may produce
distorted results. This method is not accurate when examining
the raw material of the base surface, and the solder area is
usually analysed along with the entire metal surface, which
can distort the quantitative reading of elements (Ottenwelter
et al. 2014). Nevertheless, studying ornaments by surface
techniques we obtain preliminary information about their
structure and chemical composition. In order to compare the
raw material of alloys and silversmiths used in early medieval
Europe, it is necessary to continue systematic archaeometric
research on similar ornaments, also with the use of invasive
preparation (Kolářová et al. 2014) in order to establish a database of comparative data.
Studies on aesthetically and technologically advanced artefacts from the Early Middle Ages reveal a completely new
aspect of the Slavic culture and are the basis for undertaking
international cooperation in methodological research on similar finds from the Czech Republic and Scandinavia.
Submitted results confirm a crucial role played by different
complementary analytical techniques, in particular SEMEDX, LA-ICP-MS and also lead isotope ratios and statistical
methods in order to identify combined techniques used in
silver ornaments and to establish the origin of the raw
material.
Funding information This work was has been carried out with the financial support of the National Research Centre in Cracow, Poland (grant no.
UMO-2013/09/B/HS3/03289).
Conclusions
The obtained results provide detailed information about the
technological aspects of early medieval silver ornaments from
Central and Eastern Europe and allow for an isolation of two
types of soldering. In the future, on the basis of studies on
larger assemblages, it may be possible to propose a new and
more relevant archaeological classification of these finds. This
classification can be regarded as valid after a thorough examination and comparison of all the studies of ornaments from
other West Slavic and Scandinavian territories. Research on
jewellery allows to introduce the Slavic tradition to the art
history and material culture of Europe. Until now, this tradition has been largely unknown to the world science due to the
lack of relevant studies. So far, Polish scholars have made
only one attempt at solving the problem of similarity of technological decorations in the Slavic territories. Unfortunately,
this study was based on insufficient source materials (ZollAdamikowa et al. 1999). The latest work of Czech researchers
is very promising (Čáp et al. 2011; Galuška 2013; Ottenwelter
et al. 2014; Macháček et al. 2016; Kolářová et al. 2014).
Open Access This article is distributed under the terms of the Creative
Commons Attribution 4.0 International License (http://
creativecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a link
to the Creative Commons license, and indicate if changes were made.
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