Volume XII
●
Issue 1/2021
●
Pages 45–67
InterdIscIplInarIa archaeologIca
natural scIences In archaeology
homepage: http://www.iansa.eu
XII/1/2021
possibilities and limitations of non-Invasive analytical Methods in the
examination of garnet- and niello-Inlaid precious Metal objects –
case study of three polychrome animal-style silver Buckles
from the 5th-century carpathian Basin
Viktória Mozgai1*, eszter horváth2, Bernadett Bajnóczi1
1
Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network (ELKH),
Budaörsi út 45, 1112 Budapest, Hungary
2
Department of Archaeometry and Archaeological Methodology, Institute of Archaeological Sciences, Eötvös Loránd University, Múzeum körút 4/B,
1088 Budapest, Hungary
ARtICLE INfo
ABStRACt
Article history:
received: 9th September 2020
accepted: 12th April 2021
the use of non-destructive and non-invasive analytical methods is widespread in the archaeometric
study of metal objects, particularly in the case of precious metal artefacts, from which sampling is not,
or in a limited way, allowed due to their high value. In this study, we highlight the main advantages and
limitations of non-destructive analytical methods used on three polychrome animal-style silver buckles
from the mid-to-late-5th-century carpathian Basin. optical microscopic observations, handheld XrF,
seM-edX and µ-Xrd analyses were performed to determine the chemical composition of the metals
and their decoration (gilding, garnet and niello inlays), as well as the microtexture and mineralogical
composition of the niello, in order to gain a better understanding of the materials used and reconstruct
the manufacturing techniques in detail. the buckles were manufactured from relatively high-quality
silver derived from the re-use of gilded silver scrap metal and intentionally alloyed with brass or leaded
brass. The presence of mercury indicated the use of fire gilding. The niello inlays are composed of
mixed silver-copper sulphides, even reaching the composition of pure copper sulphide; this is the first
time, when copper sulphide niello is observed on a silver object. the almandine garnets most probably
originate from southern India and sri lanka.
DOI: http://dx.doi.org/10.24916/iansa.2021.1.4
Key words:
polychrome precious metal object
carpathian Basin
garnet provenance
gilding
hXrF
seM-edX
µ-Xrd
1. Introduction
the use of non-destructive and non-invasive analytical
methods is widespread in the archaeometric study of metal
objects, particularly in the case of precious metal artefacts,
from which sampling is not allowed (or only in a very limited
way) due to their high value. however, beside the advantage
of their non-destructive nature, each analytical method has
its own limitations as well, which have to be taken into
consideration during data evaluation and interpretation (e.g.,
precision, accuracy, surface morphology, surface alterations,
and object size). the advantages and limitations of non*corresponding author. e-mail: mozgai.viktoria@csfk.org
destructive analytical methods are presented in this paper
in connection with the detailed archaeometric study of three
cast, silver, rhomboid belt buckles from the second half of
the 5th century ad (Figure 1).
this study aims to determine the elemental composition
of the metal alloy and characterise the decoration
techniques (gilding, niello and garnet inlays). the
different character of these four components set different
opportunities and limitations to the investigation. the
analysis of metal alloy has significance primarily in the
reconstruction of the organisational background of the
production; i.e., in revealing the sort of preceding use and
application phases, which attests the economic value of
the given raw materials in the period, and on the other
45
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
0
0
0
10 cm
10 cm
10 cm
0
10 cm
Figure 1. the analysed polychrome animal-style rhomboid silver buckles. a: the buckle from Zsibót-domolospuszta (buckle Zsd) (Janus pannonius
Museum, Pécs); B: the buckle from Bácsordas (Karavukovo) (buckle B/K) (Hungarian National Museum, Budapest); C: the buckle with an unknown
provenance (buckle up) (hungarian national Museum, Budapest). the tongues associated with the buckle with unknown provenance (buckle up).
d: tongue decorated with a bird’s head; e: tongue decorated with a bird and boar head (photos: e. horváth).
hand, in assessing the presence of any alloying practice and
standardisation.
From the middle of the 5th century ad, silver became
a more important raw material than gold. the combination
of these two precious metals provided a new opportunity to
enhance the polychrome effect. The use of uncoated gold
material or gold plates on silver objects, typical for the
Hunnic Period, was superseded by the use of (fire)gilding
(horváth et al., 2019; Mozgai et al., 2019b).
In the case of niello, a black silver and/or copper sulphide
inlaying material, its artificial, recipe-like character is
the key to identify the process of its making and fusing.
Dissimilarities in the composition and technology may reflect
different goldsmithing traditions or even workshop practices.
since the discussed buckles have close relations with late
46
roman military equipment in several aspects (Böhme,
1974), determination of the mineralogical composition and
microtexture of niello inlays may provide relevant new
results. analytical data are expected to prove or disprove the
continuity of the late roman niello recipes and technology.
In contrast with the silver alloy and niello inlay,
the garnet inlays represent a primary raw material of
natural origin. during data evaluation, no chemical
transformation/alteration or human intervention needs to
be considered. therefore, in the case of garnet, we could
target the localisation of potential geological sources or
the identification of their character (e.g., alluvial or mined
garnet). the proportions of major, minor and trace elements,
as well as the combination of special inclusions, have proved
to be the fingerprint evidence for (certain/particular) garnet
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
provenances. corresponding archaeometric investigations
are being performed worldwide, used as a reference for our
new measurements (e.g., Greiff, 1998; Calligaro et al., 2002;
gilg et al., 2010; Schmetzer et al., 2017; Calligaro and Périn,
2019; Pion et al., 2020; Then-Obłuska et al., 2021). These
studies are performed in order to extend our knowledge
about the used trade links and the organisational background
of supply in the early Middle ages, when garnet inlaid
jewellery had an unprecedented spread.
2. Archaeological background and analysed artefacts
the belt buckles involved in the analysis represent one of
the most emblematic metal artefacts in the middle-second
half of the 5th century ad. their main characteristics are
the silver metal, the rhomboid shape and the decoration in
polychrome animal style (table 1; Figure 1). all of the three
examples discussed here are from the Middle danube region
(Figures 1–2). The first one is from Zsibót-Domolospuszta
Table 1. the analysed polychrome animal-style rhomboid silver buckles, their decoration techniques and the number of garnet inlays. l: length; h: height;
W: width.
Provenance site
Zsibót-domolospuszta
unknown
(hungary)
Bácsordas
(Karavukovo)
Abbreviated
name
Sizes
l: 15.3 cm
buckle Zsd W: 6.3 cm
H: 0.5 cm
l: 22.1 cm
buckle up W: 7.4 cm
H: 3.7 cm
L: 14.7 cm
buckle B/K W: 5.9 cm
H: 2.7 cm
Decoration techniques
Garnet inlays
(original/missing)
Chip-carving Gilding Niello inlays Garnet inlays Loop Tongue Plate
X
X
X
X
–
2/0
14/2
X
X
X
X
4/1
2/1–4/3
40/15
X
X
X
X
–
2/1
10/0
0
10 cm
Figure 2. distribution of cast silver rhomboid belt buckles with polychrome ornamentation in the Middle danube region (after horváth et al., 2013).
1: Zsibót-Domolospuszta; 2: Bácsordas (Karavukovo); 3: Gáva; 4: Gyula; 5: Kiskunfélegyháza; 6: Dombóvár. Red: analysed in the present study; blue:
previously analysed (horváth et al., 2013); black: not yet analysed. Note that an additional buckle analysed in the present study (buckle UP) is from
an unknown hungarian site.
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Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
(hereafter called: buckle Zsd; Baranya county, hungary;
Figure 1a), the second one from Bácsordas (hereafter called:
buckle B/K; present-day Karavukovo, West-Bačka District,
serbia; Figure 1B), and the third one from an unknown
hungarian site (hereafter called: buckle up; Figure 1c). two
of the buckles were unearthed as grave goods (Dombay, 1956;
Csallány, 1961; Kiss, 1983), while the third one (buckle UP)
is a stray find brought to light in the late 19th century (hampel,
1905).
these examples have around a dozen close analogies
spread around by the great Migrations (4th–5th centuries
ad) from the Middle danube region to northern Italy and
even beyond this main distribution area (Bierbauer, 1975).
only one of them, the buckle from gáva (szabolcs-szatmárBereg county, hungary; hampel 1911; Figure 2), had been
investigated by archaeometric analysis (horváth et al., 2013).
using the available data, we are focusing on this buckle as a
highlighted item of comparison in our study.
Besides their common material and technological traits,
the polychrome animal-style buckles can be classified by
ornamentation and style. the items discussed here represent
three ornamental and stylistic subgroups. Buckles in the first
subgroup (buckles from Bácsordas and Zsibót) are decorated
by full-figure representations of birds with their heads bowed
down, and a round or drop-shaped garnet inlay in the middle
of the front-plate (Figure 1a–B). In the second subgroup (the
buckle of unknown provenance), the front-plate is framed
with a bird-head frieze. In the middle of the plate, there
are garnet inlays in rhomboid shape cloisonné (cellwork)
(Figure 1c). the third subgroup (the buckle from gáva)
represents the so-called mask buckles (Maskenschallen) that
are characterised by a mask motif and a plate closing in the
shape of a wild animal’s head, flanked by two bird heads
(Figure 2).
these buckles were unique prestige objects of the midto-late 5th-century female aristocracy. they were produced
and worn in a short period spanning one or two generations.
These approximately fifty years represent a transition period
in the history of fine metalwork in the Carpathian Basin,
between the hunnic period (early-to-mid 5th century ad)
rich in unique luxury objects and the Langobardic/Gepidic
Period (first two thirds of the 6th century ad) in which mass
products were more typical. In the hunnic period, hammered
and soldered gold objects are abundant, whereas the
Langobardic/Gepidic Period can be characterised by cast,
gilded silver objects (Horváth, 2013). Continuity or changes
of the goldsmithing traditions and their organisational
background are expected to be manifested on these objects.
the studied buckles were constructed of three, separately
cast elements and a hammered piece. the former, i.e., the
rhomboid-shaped, highly decorated front-plate (body), the
round or oval loop and the strongly profiled tongue were
joined to each other by hinge and hook. the fourth element,
an undecorated thin back-plate, which might have served to
clamp the belt, was fastened by rivets. among the analysed
objects, the back-plate was preserved only on buckle Zsd
(Figure 1a). Broken remains of fastening rivets suggest that
originally, similar back-plates might have been attached to
the rhomboid body of the other buckles too (Figure 1B–c).
the cast parts were manufactured by lost-wax casting,
using wax-models (Axboe, 1984). These models were most
probably prepared by applying two-part auxiliary moulds,
which represented the negative version of the main design:
the base form and most of the chip-carving ornamentation.
the wax model itself represented the positive, i.e. identical
version of the artefact (Genrich, 1977/1978). Further details,
such as cavities for inlays, holes for fastening rivets and
even some of the punch marks were created at this stage by
modelling the wax. the casting resulted in an intermediary
design of the artefact; the following post-casting process
included the decorative techniques and at the end, the
construction of the separately made elements.
Figure 3.
The different decoration
techniques used on the buckles resulting
in the polychrome effect on the example
of buckle B/K: chip-carving (black arrow),
gilding (yellow arrows), niello inlaying
(blue arrows), garnet inlaying (red arrows)
(photo: e. horváth).
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IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
the characteristic polychrome decoration appears in the
colouring effects of the niello- and garnet-inlaid, gilded silver
material as well as in the light-shadow effect of the chipcarved ornamentation (Figure 3; Riegl, 1927). Although both
niello and garnet inlays occur on fine metalwork in a variety
of periods and geographic areas, the combination of these
two is a speciality, typical only for the mid-to-late 5th-century
Middle Danube Region (Nagy, 2007).
Buckles B and Zsd were preserved in their original (in
some places incomplete) state during restoration, while the
broken hinge of buckle up was reinforced with a modern
supplement (Figure 1c).
two loose tongues were supposed as potential accessories
that belonged to buckle up; one of these has an ornament
in the shape of a bird’s head, while the other is decorated
with a bird and boar head (Figure 1d–e). as a detailed
archaeometric analysis had not been conducted before, it
was unclear which of these tongues could originally belong
to buckle up. the tongue with a bird’s head has the richest
niello decoration. this artefact has a unique ornamentation,
as niello mass was applied irregularly on the inner surface
of the tongue in addition to the pre-made (punched, carved)
depressions (Figure 1c).
3. Methodology
In accordance with the artefact protection regulations, only
non-destructive and non-invasive methods were allowed to
be used. In addition, the size of the objects also limited the
range of available methods and analytical equipment that
could be used, requiring the use of either handheld equipment
and/or instruments with a large sample chamber (Table 2).
Furthermore, the surface and accessibility of the measurement
points were not always optimal either. the polished surface
of the flat garnet inlays resulted in a measurement condition
similar to that of polished sections, whereas in the case of
metal alloys we had to take into consideration the effect of
post-burial alteration (e.g., corrosion processes). post-burial
alteration did not modify the mineralogy of the inlays (e.g.,
Table 2. Advantages and limitations of the analytical methods used in the present study. *after Mass and Matsen, 2013; **after Mozgai et al., 2019a.
Analytical method
hXrF*
seM-edX
Application
Pros
– chemical composition
– simultaneous, multi-element
method
– full concentration range (Z=12–92)
– major, minor, trace elements
– fast
– cheap
– portable
– non-destructive
– no sampling is needed (noninvasive)
– in most cases, no sample
preparation is needed
– chemical composition and
microtexture
– major and minor elements
– elemental mapping
– imaging at high magnifications
(tool marks, wear traces, etc.)
– fast
– surface method (upper few
– cheap
micrometres) (inhomogeneities in
– small spot size (1 µm)
the object and surface treatments)
– non-destructive
– geometric limitations (flat surfaces
– no sampling or special sample
are needed)
preparation are needed for
– sample chamber limits the size of
conductive materials (non-invasive) the objects to be analysed
– in case of non-conductive materials
(e.g. garnets, glass inlays) special
sample preparation is needed
– standardisation
– mineralogical composition (phase – fast
identification)
– non-destructive
– no sampling or special sample
preparation is needed (noninvasive)
– spot size: 10–800 µm
µ-Xrd**
Cons
– surface method (upper few tens
or hundreds of micrometres)
(inhomogeneities in the objects
due to e.g., phase segregation,
corrosion, surface treatments)
– geometric limitations (flat surfaces
are needed)
– standardisation
– geometric limitations (the object/
sample may cover certain areas of
the detector, some higher dhkl values
cannot be detected)
– the sample/object is neither
single crystal, nor represent ideal
powder, therefore the measured
peak intensities are increased
or decreased in specific hkl
crystallographic directions due to
preferred orientation
– during data evaluation only peak
positions can be used
– the smaller collimator is used, the
longer measurement time is needed
– sample size is limited
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Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
garnet or niello), only corrosion products of the metal can
deposit on their surfaces. however, during the corrosion of
precious metal objects (e.g., silver alloys), the base metals
(copper, lead) are leached out and silver and gold is enriched
towards the surface (Hall, 1961; Lejček et al., 2010).
The buckles were at first thoroughly observed with optical
microscopy to characterise the manufacturing techniques,
tool marks and garnet inclusions. the chemical composition
of the metal alloy and the gilding was analysed by using
handheld X-ray fluorescence spectrometry. No surface
cleaning was performed prior to the measurements, and we
tried to analyse the least corroded parts and as flat surfaces as
possible avoiding the contamination/disturbance of gilding
and niello inlays. the high value of the objects meant that it
was not appropriate to abrade the surface in order to expose
the underlying metal over an area of about 3 mm in diameter
(~10 mm2); large enough to match the XrF beam, especially
on the highly decorated, clearly visible sides; therefore, the
reverse, undecorated sides were measured. each part of the
buckles was analysed at 1–2 points. the hXrF is not an ideal
method for analysing niello and garnet inlays. the niello
inlays are too small and could not be analysed separately
from the metal alloy. In addition, due to limitations of the
built-in calibrations of hXrF, the exact composition of the
garnet inlays could not be determined either. therefore,
seM-edX was used to determine the chemical composition
and microtexture of the niello inlays as well as the chemical
composition of the garnet inlays.
as garnets are non-conductive materials, a special sample
preparation was needed (Bendő et al., 2013). Garnets were
first cleaned by ethanol or acetone, after the whole object
was wrapped by using aluminium foil and carbon tapes.
the foil was pierced above the garnets, leaving a small
“window” to be carbon coated. after the coating process,
the object is unwrapped making it possible to analyse the
garnet and niello inlays and the metal alloy simultaneously.
as surface treatments (e.g., paraloid B-72) can highly affect
the imaging, the analysed area was thoroughly cleaned with
acetone or ethanol. Analyses of non-flat surfaces are even
more problematic in the case of seM-edX than in the case
of hXrF; therefore, we tried to analyse surfaces that are as
flat as possible. The carbon coating was removed from the
polished garnet surfaces immediately after measurements by
using ethanol and gentle manual rubbing.
the mineralogical composition of the niello inlays of the
buckles presumed on account of the seM-edX results was
verified with the use of micro-X-ray diffractometry.
3.1 Optical microscopy (OM)
Zeiss SteREO Discovery V12 and V20 modular stereo
microscopes and a Zeiss axioscope a1 upright light
microscope equipped with a Zeiss axiocam Mrc5
microscope camera (5Mp) were used.
3.2 Handheld X-ray fluorescence spectrometry (hXRF)
A SPECTRO xSORT Combi handheld X-ray fluorescence
spectrometer was used. Analytical conditions: 15–50 kV,
50
30–120 µA, Rh anode, Peltier cooling SDD detector, “Light
elements” built-in calibration, 3 mm measurement area,
30 sec acquisition time. In the case of gilding, the built-in
calibration does not calculate the mercury content; therefore,
the presence of mercury can only be determined qualitatively
based on the hXrF spectra.
3.3 Scanning electron microscopy with energydispersive X-ray spectrometry (SEM-EDX)
A ZEISS EVO 40XVP scanning electron microscope equipped
with oxford Instruments Inca IsIs energy-dispersive X-ray
spectrometer (EDS) was used. Analytical conditions: 20 kV
accelerating voltage, 6 nA beam current and 30 sec acquisition
time. The results were normalised to 100 wt%. During
quantitative analysis, the following built-in factory standards
were used: Mgo, al2o3, sio2, wollastonite, ti, cr, Mn, Fe,
Fes2, cu, ag, au, and hgte. each garnet was analysed with at
least three (in the case of non-ideal surfaces more than three)
point (spots 1 µm in diameter) and one area measurements
(200 µm×200 µm). The accuracy of the garnet analyses was
determined after Locock (2008). Only the “Superior” and
“excellent” results were used for interpretation. the average
of the “Good” and/or “Fair” and/or “Poor” results were used
in those cases where no better-quality measurements were
received. the “poor-quality” data were treated separately.
3.4 Micro-X-ray diffractometry (µ-XRD)
A RIGAKU D/MAX RAPID II micro-X-ray diffractometer
(μ-XRD), which is a unique combination of a MicroMax-003
third generation microfocus, sealed tube X-ray generator
and a curved imaging plate detector, was used. the
diffractometer was operated with CuKα radiation generated
at 50 kV and 0.6 mA. A collimator 100 micrometres
in diameter and 20 min measurement time was used for
analyses. a built-in ccd camera was used to select the
measurement areas. a laser scanning readout system reads
the imaging plate detector in about 1 min. rIgaKu 2d
data processing software 2dp was used to record the
diffraction image from the laser readout. For each XRD
pattern, the interpretable 2Θ region was selected manually.
RIGAKU PDXL 1.8 integrated X-ray powder diffraction
software was used for data processing.
4. Results
4.1 Silver alloy composition
the buckles were manufactured from high-quality silver
(>80 wt%), intentionally alloyed with copper (Table 3;
Figure 4). Beside the typical minor and trace elements (gold,
lead, and bismuth), zinc was detected in each of the buckles.
The different parts (front-plate, loop, tongue, and backplate) of buckle ZsD (Figure 1a) were manufactured from
different silver alloys. The back-plate has the highest
(95.4 wt%), while the loop has the lowest silver content
(87.4 wt%). The gold, lead and zinc contents also vary in the
different parts. Buckle ZsD has the lowest zinc (0–0.6 wt%)
Description
Ag
Cu
Au
Pb
Bi
Sn
Zn
Au/Ag
Bi/Pb
Hg
the buckle from Zsibót–Domolospuszta (buckle ZsD)
loop
87.4
8.4
2.1
1.2
0.07
< lod
0.6
0.025
0.06
–
tongue
90.9
5.9
1.8
0.9
0.06
< lod
0.2
0.020
0.06
–
back-plate
95.4
2.9
1.0
0.4
0.06
< lod
< lod
0.011
0.15
–
0.016
0.04
front-plate
90.6
5.8
1.5
1.5
0.06
< lod
0.6
gilding
19.9
0.9
78.8
< lod
< lod
< lod
0.1
12.9
0.7
1.6
0.05
< lod
1.4
–
+
the buckle with unknown provenance (buckle UP)
loop
82.7
0.009
0.03
–
front-plate
87.6
8.3
1.0
0.9
0.06
< lod
1.7
0.011
0.07
–
tongue with bird-head
87.0
7.3
1.2
1.6
0.05
< lod
1.8
0.013
0.03
–
tongue with bird- and boar-head
81.0
10.3
1.0
1.6
< lod
< lod
4.0
0.013
gilding
13.9
1.3
83.9
< lod
< lod
< lod
0.2
–
+
the buckle from Bácsordas (buckle B/K)
front-plate
91.1
5.7
0.7
1.2
0.05
< lod
1.2
0.008
0.04
–
loop
89.9
5.7
0.7
2.5
0.04
< lod
1.1
0.007
0.02
–
0.008
0.04
tongue
90.5
5.3
0.8
1.8
0.07
< lod
1.2
gilding
14.4
1.4
83.7
< lod
< lod
< lod
0.1
–
+
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Table 3. Elemental composition of the silver buckles and their gilding based on the hXRF measurements. The results are given in wt%. LOD: limit of detection. The presence of mercury in the gilded areas is not
calculated, only qualitatively determined (+: mercury is present) – see Figure 8.
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IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Figure 4. composition of the three buckles based on the hXrF measurements. Black triangle: tongue with a bird’s head of the buckle up, white triangle:
tongue with a bird and boar heads of the buckle up. elemental composition of silver objects from the 5th century ad is depicted for comparison (unpublished
data).
and highest gold content (1.0–2.1 wt%) among the buckles.
The different parts (front-plate, loop, and tongue) of buckle
B/K (Figure 1B) were manufactured from a rather similar
silver alloy in terms of its silver (89.9–91.1 wt%), copper
(5.3–5.7 wt%), and gold (0.7 wt%) content. This artefact has
the lowest gold content among the buckles. In contrast, there
is a considerable difference between its parts in terms of lead
content: the loop has the highest (2.5 wt%), while the frontplate has the lowest (1.2 wt%) lead content. The zinc content
is 1.1–1.2 wt%.
The different parts (front-plate, loop and tongues) of
buckle UP (Figure 1C) were manufactured from different
low quality silver alloys (81.0–87.6 wt% Ag). The gold and
lead contents of its parts differ markedly (0.7–1.2 wt% Au;
0.9–1.6 wt% Pb). This buckle has the highest zinc content
among the analysed buckles (1.4–4.0 wt%). The composition
of the tongue with the bird’s head is similar to that of the
front-plate of the artefact, while the tongue decorated with
the bird and boar heads has the lowest silver (81.0 wt%) and
highest zinc (4.0 wt%) content among the objects.
4.2 Niello inlays
the buckles were extensively decorated with niello inlays.
the design of the niello decoration usually shows coherency
52
on buckles ZsB and B/K. In the case of buckle UP, the
ornamentation is mostly smooth and regular on the loop and
the tongue, while on the plate it is conceptually defective and
deteriorated in several places.
the elemental composition of the niello inlays is very
heterogeneous (29.8–64.2 at% Cu), even within a single
object. It is composed of different silver-copper sulphides
with different Ag:Cu ratios ranging from 1:1 to pure copper
sulphide (table 4; Figure 5). the surface of the niello inlays
is not even and flat, indicating that the niello inlays were not
polished after application (Figure 6A–B). The microtexture
of the niello shows inhomogeneities: lighter and darker
phases alternate with each other in the Bse images. In the
niello inlays of buckles Zsd and up the irregular darker
phases a few tens of micrometres in size are ag-cu sulphides
or cu-sulphides, while lighter phases are metallic silvercopper alloy (irregular shaped, a few tens of micrometres
in size) or contamination with mercury and gold (narrow
strings along the grain boundaries, a few micrometres in
size) (Figure 6C–D). In the niello of buckle B/K the irregular
darker phases a few hundreds of micrometres in size are agcu sulphides with higher copper content, while the irregular,
string-like lighter phases a few tens of micrometres in size
are Ag-Cu sulphides with higher silver content (Figure 6E).
Table 4. Elemental composition of the niello inlays based on the SEM-EDX measurements. The results are given in wt% and at%.
Cu
13.0
8.3
48.9
6.6
5.0
9.7
3.0
7.6
33.7
74.5
7.9
76.6
20.2
34.0
66.6
68.9
39.7
30.6
18.3
60.8
24.9
45.9
88.8
30.4
31.4
9.6
71.9
54.6
31.1
21.5
21.5
25.8
19.3
1.4
16.4
3.3
1.1
27.2
2.1
18.9
S
Au
Hg
2.1
15.1
0.8
1.1
1.9
0.1
1.8
15.6
20.5
0.9
14.8
6.4
21.9
14.4
9.9
19.6
12.8
23.9
20.9
15.3
19.9
7.2
15.3
12.7
6.2
17.3
12.3
16.8
7.5
10.4
16.6
2.4
19.3
16.4
9.6
11.6
10.9
13.3
10.7
9.1
0.9
0.2
15.2
0.5
10.6
14.7
1.2
0.5
10.9
8.9
12.3
11.0
at% →
Ag
Cu
70.6
76.7
21.2
73.3
80.0
73.7
83.0
75.0
31.7
2.5
72.1
1.3
46.5
31.7
7.0
6.9
27.2
37.5
52.9
12.0
42.9
21.7
2.1
35.4
25.5
65.4
4.5
16.4
34.8
48.7
45.0
43.3
50.4
97.6
56.0
91.7
97.6
37.2
94.8
51.0
21.6
13.1
48.9
11.6
8.6
15.4
5.4
12.4
35.7
63.1
14.2
64.2
27.6
36.1
58.5
62.3
41.2
34.3
25.3
56.3
28.9
45.4
84.0
36.4
34.3
15.9
62.4
52.3
37.9
24.8
27.4
28.1
23.7
2.4
21.0
5.4
1.9
29.8
3.5
23.2
S
Au
Hg
6.6
29.9
2.9
3.7
5.9
0.2
5.9
32.7
34.5
0.5
7.8
3.2
34.6
19.5
32.2
34.6
30.5
31.5
28.2
17.1
31.7
28.2
32.9
14.0
24.8
36.0
7.8
33.1
31.3
23.1
26.5
27.6
28.7
25.9
23.0
2.9
0.6
33.0
1.7
25.8
12.2
7.8
5.0
11.3
6.7
13.6
6.4
0.3
0.2
4.8
3.4
4.3
11.0
4.2
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
53
Description
wt% →
Ag
the buckle from Zsibót-Domolospuszta (buckle ZsD)
sp5
lighter
72.1
front-plate niello 1
niello 2
sp1
lighter
82.4
sp2
darker
36.0
niello 3
sp2
lighter
70.7
sp4
lighter
79.5
sp5
lighter
78.6
niello 4
sp2
lighter
77.4
sp3
lighter
77.8
niello 4
sp1
lighter
50.8
loop
sp2
darker
5.0
sp3
lightest
68.2
niello 5
sp2
darker
2.5
sp3
lightest
57.9
sp4
lighter
50.7
niello 6
sp1
darker
13.5
niello 7
sp1
darker
12.9
sp2
lighter
44.5
niello 9
sp2
darker
56.8
sp3
lighter
64.7
niello 10
sp1
darker
21.9
sp3
lightest
62.8
sp4
lighter
37.3
niello 13
sp1
darker
3.8
sp2
lighter
50.2
sp3
lighter
39.7
sp4
lightest
67.1
niello 15
sp1
darkest
8.8
sp2
darker
29.0
sp3
lighter
48.4
niello 1
sp3
lighter
71.6
tongue
sp4
darker
59.9
sp5
lighter
67.5
niello 3
sp2
darker
70.0
sp3
lighter
98.6
sp4
darker
74.5
sp5
lighter
95.8
niello 5
sp2
lighter
98.7
sp3
darker
57.6
sp4
lighter
97.4
sp5
darker
70.5
54
Table 4. Elemental composition of the niello inlays based on the SEM-EDX measurements. The results are given in wt% and at%. (Continuation)
Ag
Cu
S
30.4
21.0
36.8
44.5
60.4
53.4
50.9
13.6
30.0
71.9
41.3
38.4
33.5
52.4
62.9
46.2
38.8
29.8
32.1
36.1
68.7
51.3
7.1
42.2
46.2
47.5
17.2
16.0
17.0
16.8
9.7
14.6
13.0
17.7
18.7
2.1
16.6
15.4
19.0
27.7
82.8
50.3
94.9
45.6
39.1
35.2
62.9
97.3
18.9
38.7
87.8
40.8
16.3
39.3
93.7
57.5
80.1
78.6
37.2
93.6
19.1
29.3
39.9
53.8
12.1
36.6
3.9
38.3
46.1
50.3
26.6
2.7
62.6
49.9
9.2
43.4
69.1
46.4
4.6
29.7
13.6
14.3
47.8
4.4
62.9
58.6
46.3
18.4
5.0
13.2
1.2
16.1
14.8
14.5
10.5
18.5
11.4
3.1
15.8
14.7
14.3
1.7
12.7
6.3
7.1
15.0
2.0
18.0
12.1
13.8
Au
10.9
Hg
8.0
at% →
Ag
Cu
S
17.2
11.6
21.3
26.7
42.0
34.0
32.6
7.2
16.7
70.9
24.5
22.8
18.8
50.2
58.8
45.5
39.5
35.2
34.7
39.3
61.5
48.4
12.0
42.4
46.5
45.3
32.6
29.7
33.2
33.8
22.8
31.3
28.1
31.3
34.9
7.1
33.1
30.7
35.9
15.3
68.8
32.1
89.9
27.7
23.4
20.8
43.9
95.4
10.1
23.9
77.2
24.3
8.9
23.7
87.4
38.2
64.4
62.0
22.0
86.7
10.3
17.3
24.2
50.5
17.1
39.7
6.2
39.4
46.8
50.4
31.5
4.6
56.7
52.3
13.7
44.0
64.1
47.4
7.3
33.5
18.5
19.2
48.1
6.9
57.3
58.7
47.6
34.2
14.1
28.3
3.9
32.9
29.8
28.8
24.6
33.2
23.8
9.0
31.7
27.0
29.0
5.3
28.4
17.0
18.8
29.9
6.4
32.5
24.0
28.2
Au
Hg
5.9
4.2
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Description
wt% →
the buckle with unknown provenance (buckle UP)
sp3
lighter
front-plate niello 1
sp4
darker
niello 2
sp2
darker
sp3
lighter
sp1
lighter
sp2
darker
sp4
lighter
sp5
darker
sp1
lighter
sp2
lightest
sp3
lighter
sp5
lighter
sp6
darker
the buckle from Bácsordas (buckle B/K)
niello 3
sp1
darker
plate
sp3
lighter
sp1
lighter
sp2
lightest
sp4
darker
niello 4
sp1
darker
sp2
darker
sp3
lighter
sp3
lightest
sp4
darker
sp5
lighter
niello 5
sp1
lighter
sp2
darker
sp3
darkest
niello 4
sp1
darker
sp2
lighter
sp1
darker
sp2
lighter
niello 6
sp1
lighter
sp3
darker
sp1
lighter
sp2
darker
sp4
darker
sp5
lighter
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Figure 5. Composition of the niello inlays of the buckles based on SEM-EDX measurements. Chemical ranges for different silver-copper sulphides are
based on Grybeck and Finney (1968) for jalpaite (Ag1.55cu0.45s-ag1.5cu0.5s); skinner et al. (1966) and Kolitsch (2010) for mckinstryite (Ag1.18cu0.82sag1.25cu0.75s), and Frueh (1955) and tokuhara et al. (2009) for stromeyerite (Ag0.9cu1.1s-ag1.0cu1.0s), respectively.
the results of the µ-Xrd measurements proved the
presence of stromeyerite (agcus), digenite (cu9s5)
and metallic silver in the niello inlays of the buckles
(Figure 7A–C). The niello inlay of the tongue with bird and
boar heads was studied only by using µ-Xrd and revealed
that the niello inlay is composed not only of stromeyerite
and metallic silver, but also jalpaite (ag3cus4) and acanthite
(ag2S) (Figure 7D).
4.3 Gilding
the buckles were extensively gilded. the gold content of the
gilded areas is around or above 80 wt% on each buckle based
on the hXrF measurements (table 3), indicating a rather
thick gilding. the thickness of the gilding is estimated to be
around several tens of micrometres based on Bse images
(Figure 6F). Mercury was detected in the gilded areas by
hXRF and SEM-EDX measurements as well (Figure 8).
4.4 Garnet inlays
red garnet inlays played an important role in the decoration
of the buckles. highlighting the eyes and mouth of the bird
and boar figures, they are contrasting with the colours of
precious metals and niello (Figure 3). the prevailing shape
of the garnet slabs is flat and round, although some triangular,
rectangular, lunula- and drop-shaped pieces are also present.
as these pieces are mounted, it proved impossible to analyse
the full range of mineral inclusions in the individual garnets.
this limited access is a general problem; loose, unmounted
pieces are very rarely found (Horváth and Bendő, 2011).
The detected inclusions have been identified based on
their morphology. Most of these are accessory minerals
(e.g., rutile needles, ilmenite plates, isometric zircon, and
xenomorph quartz crystals) that are not indicators for the
source rocks. From this aspect, kyanite crystals and curved
needles of sillimanite, detected in a group of the slabs, are
of greater importance since they indicate medium- to highgrade metamorphism at medium pressure (Figure 9a–B)
(spear, 1995). one typical combination of inclusions occurs
extensively in the garnets of buckle Zsd: these are extremely
fine, wavy rays of fluid inclusions accompanied by ilmenite
plates (Figure 9C–D). Another specific type of inclusion is
the large, clear apatite crystals in the garnets of the tongue
with the bird and boar heads, belonging to buckle up.
From among the 55 garnet inlays preserved in the settings
of the buckles, 45 pieces were analysed by seM-edX.
Based on the chemistry, the garnets used for inlays are
from the pyralspite (pyrop-almandine-spessartine) series,
namely almandine with varying ca, Mg and Fe contents
(Figure 10). Some garnets of buckle B/K exhibit higher
Mg concentrations, often referred to as intermediate
55
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Figure 6. Backscattered electron images of the niello inlays and gilding of the buckles. a–B: niello inlays were put in previously carved recesses, the surface
of the niello is not flat, polished or even on buckles B/K and ZsD; C: heterogeneous niello of the loop of buckle ZsD; D: heterogeneous niello of the tongue
of buckle ZsD; E: niello inlay of buckle B/K; F: rather thick gilding on the plate of buckle ZsD.
pyrope-almandine crystals (gilg et al., 2010). No ugrandite
(uvarovite-grossular-andradite) series garnet was identified
on the buckles.
5. Discussion
5.1. Silver alloy composition
the buckles were manufactured from relatively high-quality
silver (82.7–95.4 wt% Ag), which corresponds well with
56
the general trend that during the 5th-century ad a gradual
debasement of silver alloys occurred towards the end of
the century (Figure 4) (horváth et al., 2019; Mozgai et al.,
2019b). The beginning of the 5th century ad is characterised
with high-quality silver alloys with low au, pb and Zn
and varying Bi content similar to late roman silver alloys
(Hughes and Hall, 1979; Lang et al., 1984; Feugère, 1988;
Lang, 2002; Cowell and Hook, 2010; Hook and Callewaert,
2013; Doračić et al., 2015; Lang and Hughes, 2016; Greiff,
2017; Mozgai et al., 2017; Vulić et al., 2017; Mozgai et al.,
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Figure 7. typical µ-Xrd patterns of the niello from the buckles. a: tongue of buckle Zsd; B: loop of buckle Zsd; c: tongue with a bird’s head of buckle
UP; D: tongue with a bird and boar heads of buckle UP. Abbreviations: ac = acanthite (JCPDS 14-0072); jp = jalpaite (JCPDS 12-0207); str = stromeyerite
(JCPDS 75-0890); dig = digenite (JCPDS 84-1770); Ag = metallic silver (JCPDS 87-0598).
57
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Figure 8. typical XrF spectra of the gilded areas of the buckles.
Figure 9. Typical mineral inclusions in the garnets of the buckles. A: buckle B/K; B: buckle UP; C–D: buckle ZsD (photos: E. Horváth).
58
IANSA 2021 ● XII/1 ● 45–67
Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Figure 10. ternary plots showing the composition of the garnets from the buckles based on the cation occupancy of the X site in the garnet structure
calculated from the seM-edX data (after grew et al., 2013). Black triangle: tongue with a bird’s head of buckle UP, white triangle: tongue with a bird
and boar heads of buckle up.
2020; Mozgai et al. 2021). In contrast, lower quality silver
alloys with high cu, pb, Zn and sn content, reaching even the
1:1 ag:cu ratio (Figure 4), are more typical for the end of the
5th century ad (horváth et al., 2019; Mozgai et al., 2019b).
pure silver is too soft for making silver objects of use,
because they would have a tendency to suffer dents, and
bend and wear easily. the most common alloying metal in
silver is copper, which improves the mechanical properties
of soft silver (e.g., increases strength and durability). during
silver extraction, the copper content could be reduced to even
0.2–1 %; therefore, higher copper concentration indicates
intentional alloying (Hughes and Hall, 1979).
the measured elements other than silver and copper are
naturally occurring, unintentionally or intentionally added
elements, deriving from the silver ore or from the copper
(bronze, brass) used for alloying (Hughes and Hall, 1979).
In antiquity, the main source of silver was silverbearing lead ores (Tylecote, 1962; Forbes, 1971). The
silver ores were roasted, melted and cupelled during silver
extraction. Cupellation separates silver very efficiently
from impurities (mainly from antimony, arsenic, tin, iron,
and zinc; less well from copper, gold and bismuth). the
volatile elements (antimony, arsenic, mercury, tin and zinc)
disappear from molten silver during cupellation (pernicka,
2014; L’Héritier et al., 2015). Therefore, the elevated zinc
content (0.2–4.0 wt% Zn) of the buckles indicates that not
pure copper, but brass was added to the silver as an alloying
metal. The most important benefit of alloying is that it lowers
the melting point. the more copper is added to molten
silver; the more yellowish tint the alloy will have. this can
be overcome by adding zinc to the alloy, which will act as a
sort of “whitener” upgrading the colour (Greiff, 2012). The
addition of zinc also prevents molten silver from oxidation and
bubbling, and enhances tarnish-proofness resulting in a much
nicer polish (Greiff, 2012). The addition of tin has a similar
effect on colour and tarnish-proofness. Moreover, it enhances
ductility making tin-enriched silver alloys more ideal for sheet
production (Greiff, 2012). It is uncertain whether 5th-century
goldsmiths were aware of these effects and intentionally
alloyed the silver with Zn (or sn), beside copper.
If silver originates from silver-bearing lead ores (galena,
anglesite or cerussite), the lead content in the silver alloy
ranges between 0.001% and 3% (Moorey, 1985). The lead
content of cupelled silver is typically between 0.5 and
1.2 wt% (Greiff, 2012). The lead content of the buckles
shows generally higher concentrations (0.4–2.8 wt% Pb),
indicating that leaded copper or leaded brass was used for
alloying.
Bismuth is a good geochemical indicator that helps
identifying the provenance of silver objects, as its concentration
remains relatively constant during cupellation (pernicka and
Bachmann, 1983; Pernicka, 2014; L’Héritier et al., 2015).
Based on experiments, bismuth is oxidised only in the very
last stages of cupellation and, therefore, bismuth in silver
objects is correlated with the degree of cupellation. however,
the final Bi/Pb ratio of the cupelled silver depends on the
initial Bi content of the silver-bearing lead ores (l’héritier
et al., 2015). The Bi/Pb ratio of the buckles is rather low and
consistent, except the back-plate of buckle Zsd (Figure 4),
which is typical for the silver alloys from the middle and end
of the 5th century ad (horváth et al., 2019; Mozgai et al.,
2019b), in contrast with silver alloys from the beginning of the
5th century ad and from late roman times. the latter usually
have more varied Bi/Pb ratios, indicating the use of silver from
different ore sources (Cowell and Hook, 2010; Doračić et al.,
2015; Greiff, 2017; Mozgai et al., 2017; Vulić et al., 2017;
Mozgai et al., 2020; Mozgai et al. 2021). The more constant
Bi/Pb ratio in silver objects from the middle and end of the
59
60
Table 5. Chemical composition of the garnet inlays based on the SEM-EDX measurements. The results are given in wt%. The accuracy of the garnet analyses was determined after Locock (2008). Only the
“Superior” and “Excellent” results were used and their average and std. deviation were calculated. The average and std. deviation of the “Good” and/or “Fair” and/or “Poor” results were used in those cases where
no better-quality data were received. No.: number of analyses used to calculate the average and std. deviation values after Locock (2008).
No.
SiO2
Al2O3
MgO
CaO
MnO
FeO
3
1
2
4
5
1
3
4
1
4
2
2
1
34.5±0.3
32.7
38.6
36.6±3.0
36.2±1.7
47.9
42.0±1.1
46.5±1.5
40.8
46.2±1.3
41.8
35.3
39.6
18.0±0.2
17.3
20.6
19.0±1.7
19.2±1.0
25.9
22.1±0.5
24.3±0.9
22.0
25.1±0.4
22.3
19.6
21.3
3.6±0.1
3.3
4.8
4.2±0.5
6.7±0.5
5.8
3.9±0.2
4.2±0.4
5.4
6.9±0.3
7.8
3.1
4.4
3.7±0.2
2.0
3.1
1.9±0.4
2.9±0.3
2.2
2.6±0.2
2.8±0.3
2.3
1.3±0.3
3.3
2.4
1.4
0.4±0.3
1.0
31.5±1.4
31.4
34.7
34.0±2.3
27.3±1.2
43.4
38.3±0.7
41.1±1.5
37.8
34.4±0.5
31.4
33.2
32.9
1
4
1
1
1
4
1
1
3
2
1
8
1
1
1
4
4
2
1
3
3
38.9
38.0±0.3
35.8
40.0
37.2
39.7±0.5
38.0
39.0
40.3±1.0
38.5
40.5
40.1±0.5
39.7
38.9
38.0
38.1±0.8
37.8±0.3
38.8
40.0
37.2±0.5
37.6±0.5
15.8
19.4±0.2
17.9
20.4
20.9
21.0±0.9
17.9
20.4
19.1±2.8
20.2
20.8
20.8±0.8
18.8
21.6
21.1
19.8±1.0
20.0±0.3
20.3
21.5
19.5±0.2
19.9±0.4
6.4
5.8±0.1
5.3
7.8
5.4
6.7±0.4
6.5
7.5
8.5±0.7
7.2
6.9
6.3±0.3
11.0
6.4
6.1
6.6±1.1
6.0±0.2
8.1
6.8
5.2±0.2
6.5±0.2
0.5
1.6±0.1
1.6
1.0
1.4
1.2±0.5
1.3
1.6
0.9±0.8
1.6
1.0
1.3±0.2
1.4
1.6
1.8±0.5
1.5±0.2
1.6
1.4
2.8±0.2
1.5±0.2
0.5±0.3
0.4
2.1±0.4
4.2±0.6
0.1
3.5±0.3
0.5
1.6
0.5
1.8±0.4
2.1
0.6
2.0
1.2±0.2
1.2
0.3
0.8
0.3
1.7±0.3
2.3
3.3
1.2±0.1
1.1±0.2
1.2
1.2±0.2
40.2
33.5±0.7
37.4
29.9
32.9
30.1±0.6
34.9
31.5
31.0±2.9
31.7
30.3
29.7±0.7
32.1
29.3
29.7
32.6±2.5
33.3±0.3
31.4
29.5
35.4±0.1
33.3±0.4
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Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
Description
the buckle from Zsibót-Domolospuszta (buckle ZsD)
grt 1
front-plate
grt 2
grt 3
grt 4
grt 5
grt 6
grt 7
grt 8
grt 10
grt 11
grt 12
grt
1
tongue
grt 2
the buckle with unknown provenance (buckle UP)
grt 1
front-plate
grt 2
grt 3
grt 4
grt 5
grt 6
grt 7
grt 8
grt 9
grt 10
grt 11
grt 12
grt 13
grt 14
grt 15
grt 17
grt 19
grt 20
grt 21
grt 22
grt 23
1.5
0.5
0.8±0.2
33.1±0.7
18.0±0.2
21.7
24.2±0.4
34.6
29.9
31.6
23.2
33.6±0.8
1.3±0.2
0.2±0.1
0.3
0.5±0.03
0.7
0.8±0.2
0.5±0.01
3.3
2.3±0.2
1.3
1.3
1.6
2.1
0.8±0.1
20.1±0.2
22.6±0.4
21.4
21.5±0.1
19.9
21.0
20.7
21.7
20.0±0.7
38.1±0.6
42.5±0.2
40.8
40.8±0.2
37.7
40.0
38.4
41.1
37.9±0.6
4
3
1
3
2
2
1
2
4
6.4±0.2
16.3±0.2
12.3
10.5±0.4
5.9
7.6
6.0
11.3
6.6±0.3
FeO
24.6
30.7
MnO
0.8
1.0
CaO
4.5
1.4
MgO
8.7
6.8
Al2O3
21.0
21.3
SiO2
40.6
39.1
No.
1
1
Description
tongue with bird- and boar-head grt 1
grt 1
tongue with bird-head
the buckle from Bácsordas (buckle B/K)
grt 2
front-plate
grt 3
grt 4
grt 5
grt 6
grt 7
grt 8
grt 9
grt 10
Table 5. Chemical composition of the garnet inlays based on the SEM-EDX measurements. The results are given in wt%. The accuracy of the garnet analyses was determined after Locock (2008). Only the
“Superior” and “Excellent” results were used and their average and std. deviation were calculated. The average and std. deviation of the “Good” and/or “Fair” and/or “Poor” results were used in those cases where
no better-quality data were received. No.: number of analyses used to calculate the average and std. deviation values after Locock (2008). (Continuation)
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Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
5th century ad may be the result of gradual recycling and
mixing of different silver alloys, and therefore, in our case,
the Bi/Pb ratio is not indicative of provenance.
gold is completely miscible with silver. during
metallurgical processes, the gold content of the silver
does not change radically (l’héritier et al., 2015), and as
a consequence, the Au/Ag ratio remains constant during
cupellation (Pernicka, 2014). The buckles show elevated
concentrations of gold (0.7–2.1 wt% Au), and, as a result,
elevated Au/Ag ratios (Figure 4). Various interpretations
are possible for higher gold concentrations, e.g., remnants
of former gilding, the re-use of scrap gilded silver, or the
use of gold-silver ores. In the case of buckles, as recycling
was proven by other elements as well, it is safe to say that
most probably re-used scrap gilded silver was utilised for
manufacturing.
the polychrome animal-style silver buckle from gáva,
previously analysed by horváth et al. (2013), exhibits
slightly lower silver (81.5–82.5 wt%) and higher lead content
(1.9–2.8 wt%) than the three buckles discussed in this study.
The gold content is, however, similar (0.8–1.0 wt%). The
main difference is that beside zinc (1.9–2.5 wt%), elevated
tin content (5.5–5.8 wt%) was also detected in the buckle
from gáva, indicating the use of leaded bronze or gunmetal
for alloying.
The differences in the elemental composition of the
silver alloys indicate the use of different silver alloys in
manufacture. the shortage of raw materials towards the end
of the 5th century ad resulted in the re-use and recycling
of more diverse materials. Furthermore, the differences in
alloy compositions, even within one single object, indicate
that there was no conscious or standardised alloying practice
adopted by 5th-century ad goldsmiths.
the only undecorated back-plate that was analysed in the
study, used for fastening the strap/belt, belongs to buckle
ZsD. Its composition differs completely from the other parts
of the buckle and shows similarities to late roman silver
alloys (high silver content, relatively low gold, lead and
copper content, and no zinc) (Figure 4). It may have been
manufactured by melting roman silver objects directly,
without further alloying.
5.2 Niello inlays
the bluish-black niello has been widely used to decorate
silver, gold and copper-based alloy objects. chemically,
niello is composed of the sulphide of one or more metals,
fused or inlaid into a recess carved into the metal surface.
the composition of niello changed over the course of time
depending on what type of metal it decorated (rosenberg,
1908; Moss, 1953; Dennis, 1979; Newman et al., 1982;
La Niece, 1983; Oddy et al., 1983; Schweizer, 1993;
Northover and La Niece, 2009).
niello technique was much used in the early Middle
ages, but there are still uncertainties concerning the niello
technique (exact composition, preparation and application)
used in this particular period. It has been widely accepted
that during the roman period niello was generally composed
61
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Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
of the sulphide of only one metal, namely the same as the
metal it decorates: silver sulphide (acanthite ag2s) for silver
objects and mixtures of copper sulphides (chalcocite cu2s,
digenite cu9s5 and covellite cus) for copper-based alloy
objects. Intentional use of binary silver-copper sulphide
niello (stromeyerite agcus) is assumed to have started
only at the end of the 5th century ad (Moss, 1953; dennis,
1979; Newman et al., 1982; La Niece, 1983; Oddy et al.,
1983; Schweizer, 1993; Northover and La Niece, 2009).
recent studies have proved that silver-copper sulphide niello
(reaching the composition of stromeyerite) was already
being used in roman times (Mozgai et al., 2019c).
the studied buckles were decorated with silver-copper
sulphides of various Cu content (29.8–64.2 wt%), and the
µ-Xrd measurements proved the presence of stromeyerite
(agcus), digenite (cu9s5) and metallic silver. the niello
inlays of the buckle from gáva are also silver-copper sulphides
with sporadically detected lead and tin contents, which was
interpreted as niello prepared from debased silver (horváth
et al., 2013). Previous studies on niello-inlaid objects from
the 5th century ad proved the presence of mixed silver-copper
sulphides (La Niece, 1983; Craddock et al., 2010; Horváth
et al., 2013), but niello inlays with very high copper content on
silver objects, reaching even the composition of pure copper
sulphide, has not yet been described.
the use of silver-copper sulphide niello by the craftsmen
can be threefold (Mozgai et al., 2019c): (i) unintentional
use, when the goldsmith was not aware of the copper content
of the silver alloy used for the preparation of the niello;
(ii) intentional use, when the silversmith was aware of the
variable copper content of the silver alloy available to him,
but did not care; and (iii) technological innovation, when the
silversmith intentionally prepared a starting silver-copper
alloy using a recipe to gain either technological or economic
benefits.
the short supply of metals in the period could have led to
a wider use of cheaper materials and also to a more frequent
re-use of scrap metals. As there are no serious differences
either in the preparation, or in the application of the different
niello types, the final products, the different silver-copper
sulphides look exactly the same. the craftsman clearly felt
no need to distinguish between them and he did not bother to
refine recycled materials: he just used them.
the presence of metallic silver in the niello inlays can be
interpreted as not all the silver metal reacted with sulphur
during preparation or the niello decomposed at elevated
temperatures, as silver-copper sulphides start to decompose
to elemental silver in an oxidising atmosphere before
reaching their melting point (~680–860 °C) (Skinner, 1966;
Allan, 1979; La Niece, 1983; Stemann-Petersen, 1995; 2003;
Živković et al., 2013).
previous studies on objects decorated with silvercopper sulphide niello from the early medieval ages
(5th–10th century) were interpreted as their niello not
being applied in molten form (La Niece, 1983; StemannPetersen, 1995; 2003). Silver-copper sulphides are
malleable at room temperature, and even more when
62
heated; experiments proved that it is possible to inlay
niello in solid form, softening them a little by heating
to be compacted (La Niece, 1983; Stemann-Petersen,
1995; 2003). There are two usual methods described in
the literature for the application of silver-copper sulphide
niello in solid form: either in powder form or as compact
strips. In the case of the powder form the craftsman has to
grind up the niello, fill the engraved cavities with the black
powder, and after that heat the silver over a flame and rub
the powder with a burnisher repeatedly to fix it in place
and to reach a compact polishable surface (Moss, 1953;
Dennis, 1979; Newman et al., 1982; Oddy et al., 1983;
La Niece, 1983; Schweizer, 1993). Even early descriptions
report the difficulties of grinding niello as it is not brittle
enough. Recent experiments confirm these observations
(Stemann-Petersen,
1995;
2003).
Furthermore,
rubbing heated niello particles into the recesses during
experiments was difficult to control: the powder did not
become completely compacted together and did not leave
a homogeneous sulphide inlay (stemann-petersen, 1995;
2003). This can be the reason why the niello inlays of the
buckles do not look even and compact enough.
the patches of mercury and gold on the surface of the
niello inlays are the remnants of gilding, during which
mercury or gold amalgam spread over the surface of the
niello, as well as reacting with the material of the niello
forming silver amalgam.
5.3 Gilding
the buckles were extensively gilded with a relatively thick
gold layer. Mercury was detected in the gilding of the
buckles indicating the use of fire gilding. Previous studies
on objects from the 5th century ad have also proved the
use of fire gilding (Craddock et al., 2010; Horváth, 2013).
the buckle from gáva was also decorated with this type of
gilding (horváth et al., 2013).
Fire gilding was most probably invented in china in the
4th century BC (Lechtman, 1971; Lins and Oddy, 1975; Oddy,
1981; 1988; 1991; 1993; 2000). Gold was dissolved in hot
mercury and the resulting gold amalgam was rubbed on to the
cleaned metal surface, after the object was heated for a few
minutes at 250–300 °C (below the boiling point of mercury,
357 °C) until it turns from grey to yellow. It is important to
avoid any overheating of the object: if silver is overheated,
the gold will discolour or even disappear into the substrate.
This phenomenon restricts the maximum firing temperatures
to approx. 350 °C. Given this proviso, a firmly bonded, but
porous, matte gilded layer will form, which then needs to
be burnished. this technique is still used in nepal (oddy,
2000; Anheuser, 1997). In the Roman world, fire gilding
is mentioned as a rare and costly method by pliny in the
1st century ad, but became the standard method of gilding in
the 3rd–4th centuries ad and continued in use throughout the
Migration period and medieval europe until the invention
of electroplating in the mid-19th century (Lechtman, 1971;
Lins and Oddy, 1975; Oddy, 1981; 1988; 1991; 1993; 2000).
Another method of fire gilding is to apply a layer of mercury
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Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
to the metal surface to be gilded and then lay pieces of gold
leaf on top. the gold leaf dissolves in mercury creating a
gold amalgam in situ, after which the object is heated and
burnished. This method is still used in Japan (Oddy, 2000;
Anheuser, 1997). During fire gilding, 8–25 % of mercury is
retained – and thus can be later detected (Anheuser, 1997).
Fire gilding superseded gold-plating during the second
half of the 5th century ad (Mozgai et al., 2019b; Horváth
et al., 2019). This can be interpreted as less gold is needed
for fire gilding and given the shortage of raw materials,
or alternatively, fire gilding is a more complicated and
sophisticated gilding method indicating the development of
goldsmithing skills during the 5th century ad.
5.4 Garnet inlays
Metalwork objects with red gemstones, identified mostly as
garnets, were widespread during the hellenistic, roman and
Early Medieval times (Arrhenius, 1985; Adams, 2011). In
the archaeological material of the carpathian Basin, garnet
inlay decoration was a characteristic feature over around
three centuries, from the hunnic period through the age
of the gepidic and langobardic Kingdoms until the avar
Period (Horváth, 2013). Provenance studies of the tiny garnet
inlays have come into focus since the end of the last century.
Thousands of analyses and many field trips in present-day,
or at one-time, mine districts facilitated their increasingly
detailed geochemical characterisation (recently: schmetzer
et al., 2017; Calligaro and Périn, 2019; Then-Obłuska et al.,
2021). The identification and comparison of (mineral and
fluid) inclusions and chemical compositions (major, minor
and trace elements) with similar datasets of recent geological
samples has proved to be the key to the localisation of
potential geological sources.
the garnets in the buckles are almandine, and on
rare occasions intermediate pyrope-almandine, from the
pyralspite series. the chemical composition of the garnet
slabs was compared to the chemical composition of garnets
from those deposits which were certainly known and used
in the Migration period, as attested by the analyses of other
contemporaneous objects. the chemical composition and the
characteristic inclusion assemblages revealed that european
deposits can be excluded as possible sources (Figure 11).
Our data are classified into two sets: to one of the clusters
(cluster a) and to a heterogeneous group (group X)
requiring further division (gilg et al., 2010). The inlays
on the buckles B/K and UP are mainly Cluster A garnets
and only a few garnets belong to group X. contrarily, the
inlays on buckle Zsd are mainly group X garnets and only
a few cluster a garnets are present (Figure 11). the garnet
inlays on the buckle from gáva belong to both cluster a and
group X (horváth et al., 2013).
cluster a garnets, generally comprised of chromiumbearing almandines originating most probably from southern
India (Greiff, 1998; Calligaro et al., 2008; Gilg et al., 2010;
2018), are the earliest ones in use in the Migration Period
carpathian Basin, applied from the beginning of the hunnic
period (horváth et al., 2019). Group X garnets, almandines
with a higher magnesium content, originate from the placer
Figure 11. CaO-MgO plot showing the composition of the garnets based on the SEM-EDX measurements. The classification of possible provenances is
based on Greiff (1998), Quast and Schüssler (2000), Mannerstrand and Lundqvist (2003), Calligaro et al. (2008), Gilg et al. (2010; 2018). The grey area
represents garnets with variable chemical and gemmological characteristics that derive from various, unknown deposits and cover possible new clusters:
blue circle: Sri Lanka (Ratnapura?); yellow circle: Sri Lanka (Elahera?) (Calligaro and Périn, 2019); red circle: new cluster? Poor quality measurements:
based on Locock (2008). Black triangle: tongue with a bird’s head of buckle UP, white triangle: tongue with a bird and boar heads of buckle UP.
63
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Viktória Mozgai, Eszter Horváth, Bernadett Bajnóczi: Possibilities and Limitations of Non-Invasive Analytical Methods in the Examination
of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
deposits of Sri Lanka (Greiff, 1998; Calligaro et al., 2008,
gilg et al., 2010; 2018). These are very diverse chemically,
suggesting that a number of primary sources may be
involved, and the group comprises, most probably, several
clusters (gilg et al., 2010). Recent studies have further
classified Group X based on the chemical composition and
mineral inclusions of the garnets (Périn and Calligaro, 2016;
Calligaro and Périn, 2019; Gilg et al., 2019; Horváth et al., in
preparation). Based on the chemistry, garnets from ratnapura
(sri lanka) and elahera (sri lanka) deposits might be
such potential sources (Calligaro and Périn, 2019). Further
investigations are in progress on the mineral inclusions of
the garnets of these two deposits and further potential source
materials (gilg, personal communication). Most of the
garnets from buckle Zsd may originate from a third cluster
based on the chemical composition and especially on the
characteristic mineral inclusions (Figure 9c–d; Figure 11),
but investigations on geological samples are required to
prove this hypothesis. prospective measurements of the trace
elements and mineral inclusions in the future may confirm
the classification presented here based on the major and
minor element compositions.
group X and cluster a garnets were predominant all over
europe during the 5th century ad. as sri lanka and southern
India are close to each other geographically, most probably
their garnets were transported via common long-distance
maritime trade routes (Roth, 1980). No Cluster B garnets,
originating from northern India, were observed on the buckles.
northern Indian garnets became commonly used only from
the beginning of the 6th century ad (gilg et al., 2010).
each buckle is richly decorated by chip-carving, gilding,
niello and garnet inlaying. the presence of mercury indicates
the use of fire gilding. The niello inlays of the buckles are
composed of mixed silver-copper sulphides with relatively
high copper contents, even reaching the composition of pure
copper sulphide. copper sulphide niello on a silver object has
not yet been reported before. the presence of metallic silver
in the niello, the lack of final polishing, and the unevenness of
the niello’s surface suggest that it was made by an unskilled
craftsman. Based on their chemistry and mineral inclusions,
the almandine garnets of the buckles most probably derive
from southern India and sri lanka.
It is unequivocal from the similarity of the elemental
composition of its silver alloy and garnet inlays to the other
parts of the buckle that the tongue with bird’s head belonged
to buckle up originally. the tongue with bird and boar heads
could have been the accessory of another buckle.
the buckles could not be related to the work of a single
goldsmith, or workshop; it is much more likely that these
are products from workshops that operated in the same
region and followed, more or less, similar practices. the
localisation of the workshops remains an open question, but
the late roman metalwork in the provinces along the limes
must have had an impact. Based on the prevalence of the
finds and the currently available research results, one can
hypothetically localise the workshops near the centres of
barbaric power (germanic tribal kingdoms) in the former
Roman provinces, although a more precise identification yet
remains to be done in the light of further evidence.
Acknowledgements
6. Conclusion
three polychrome animal style silver buckles, dated to the
second half of the 5th century ad, were analysed in order to
determine the elemental composition of their metal alloys and
to explore techniques of their manufacture and decoration
(gilding, niello and garnet inlays). non-destructive and
non-invasive analytical methods, such as handheld XrF,
seM-edX and µ-Xrd, were successfully used, while their
limitations – such as using a special preparation technique
needed for the seM-edX analysis of mounted garnets;
in situ microtextural and mineralogical analysis of the niello
inlays, and geometric and calibration limitations – were also
kept in mind.
the buckles were manufactured from high-quality silver,
but a gradual decrease in the silver quality is evident towards
the end of the 5th century ad. the elevated lead and zinc
contents indicate that silver was intentionally alloyed with
brass and leaded brass instead of pure copper. The different
parts of the buckles have different chemical compositions,
suggesting the use of different silver alloys. The elevated
gold content implies the re-use/recycling of gilded silver
scrap metal. Re-use/recycling was made necessary by the
shortage of raw material caused mainly by the decrease of
primary mining.
64
The research was supported by the Hungarian Scientific
Research Fund granted to Eszter Horváth (OTKA/NKFIHPD109234). The authors are thankful for their help to Mária
tóth (Iggr rcaes elrn), Máté szabó (Iggr rcaes
elrn), péter németh (IMec rcns elrn), Zsuzsanna
hajnal ((hungarian national Museum, Budapest), gergely
Kovaliczky (Janus pannonius Museum, pécs) and Marianna
dági (Museum of Fine arts, Budapest).
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of Garnet- and Niello-Inlaid Precious Metal Objects – Case Study of Three Polychrome Animal-Style Silver Buckles from the 5th-Century Carpathian Basin
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