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45
XII/1/2021
InterdIscIplInarIa archaeologIca
natural scIences In archaeology
homepage: http://www.iansa.eu
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 5
th
-Century Carpathian Basin
Viktória Mozgai
1*
, Eszter Horváth
2
, Bernadett Bajnóczi
1
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
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-
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 5
th
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
diferent character of these four components set diferent
opportunities and limitations to the investigation. The
analysis of metal alloy has signifcance 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
Volume XII ● Issue 1/2021 ● Pages 45–67
*Corresponding author. E-mail: mozgai.viktoria@csfk.org
ARtICLE INfo
Article history:
Received: 9
th
September 2020
Accepted: 12
th
April 2021
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
ABStRACt
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-5
th
-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 fre gilding. The niello inlays are composed of
mixed silver-copper sulphides, even reaching the composition of pure copper sulphide; this is the frst
time, when copper sulphide niello is observed on a silver object. The almandine garnets most probably
originate from Southern India and Sri Lanka.
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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 5
th
-Century Carpathian Basin
46
hand, in assessing the presence of any alloying practice and
standardisation.
From the middle of the 5
th
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 efect. The use of uncoated gold
material or gold plates on silver objects, typical for the
Hunnic Period, was superseded by the use of (fre)gilding
(Horváth
et al.
, 2019; Mozgai
et al.
, 2019b).
In the case of niello, a black silver and/or copper sulphide
inlaying material, its artifcial, recipe-like character is
the key to identify the process of its making and fusing.
Dissimilarities in the composition and technology may refect
diferent goldsmithing traditions or even workshop practices.
Since the discussed buckles have close relations with late
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 identifcation 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 fngerprint evidence for (certain/particular) garnet
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).
0 10 cm
0 10 cm
0 10 cm
0 10 cm
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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 5
th
-Century Carpathian Basin
47
provenances. Corresponding archaeometric investigations
are being performed worldwide, used as a reference for our
new measurements (
e.g.
, Greif, 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 5
th
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 frst 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 siteAbbreviated
name
SizesDecoration techniquesGarnet inlays
(original/missing)
Chip-carvingGildingNiello inlaysGarnet inlaysLoopTonguePlate
Zsibót-Domolospusztabuckle ZsD
L: 15.3 cm
W: 6.3 cm
H: 0.5 cm
XXXX–
2/014/2
unknown
(Hungary)
buckle UP
L: 22.1 cm
W: 7.4 cm
H: 3.7 cm
XXXX
4/12/1–4/340/15
Bácsordas
(Karavukovo)
buckle B/K
L: 14.7 cm
W: 5.9 cm
H: 2.7 cm
XXXX–
2/110/0
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.
0 10 cm
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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 5
th
-Century Carpathian Basin
48
(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 fnd brought to light in the late 19
th
century (Hampel,
1905).
These examples have around a dozen close analogies
spread around by the Great Migrations (4
th
–5
th
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-Szatmár-
Bereg 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 classifed by
ornamentation and style. The items discussed here represent
three ornamental and stylistic subgroups. Buckles in the frst
subgroup (buckles from Bácsordas and Zsibót) are decorated
by full-fgure 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, fanked by two bird heads
(Figure 2).
These buckles were unique prestige objects of the mid-
to-late 5
th
-century female aristocracy. They were produced
and worn in a short period spanning one or two generations.
These approximately ffty years represent a transition period
in the history of fne metalwork in the Carpathian Basin,
between the Hunnic Period (early-to-mid 5
th
century AD)
rich in unique luxury objects and the Langobardic/Gepidic
Period (frst two thirds of the 6
th
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 profled 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 diferent decoration
techniques used on the buckles resulting
in the polychrome efect 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 5
th
-Century Carpathian Basin
49
The characteristic polychrome decoration appears in the
colouring efects of the niello- and garnet-inlaid, gilded silver
material as well as in the light-shadow efect of the chip-
carved ornamentation (Figure 3; Riegl, 1927). Although both
niello and garnet inlays occur on fne metalwork in a variety
of periods and geographic areas, the combination of these
two is a speciality, typical only for the mid-to-late 5
th
-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 fat 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 efect 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 methodApplicationProsCons
hXRF*
– 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 (non-
invasive)
– in most cases, no sample
preparation is needed
– surface method (upper few tens
or hundreds of micrometres)
(inhomogeneities in the objects
due to
e.g.
, phase segregation,
corrosion, surface treatments)
– geometric limitations (fat surfaces
are needed)
– standardisation
SEM-EDX
– chemical composition and
microtexture
– major and minor elements
– elemental mapping
– imaging at high magnifcations
(tool marks, wear traces,
etc.
)
– fast
– cheap
– small spot size (1 µm)
– non-destructive
– no sampling or special sample
preparation are needed for
conductive materials (non-invasive)
– surface method (upper few
micrometres) (inhomogeneities in
the object and surface treatments)
– geometric limitations (fat surfaces
are needed)
– sample chamber limits the size of
the objects to be analysed
– in case of non-conductive materials
(
e.g.
garnets, glass inlays) special
sample preparation is needed
– standardisation
µ-XRD**
– mineralogical composition (phase
identifcation)
– fast
– non-destructive
– no sampling or special sample
preparation is needed (non-
invasive)
– spot size: 10–800 µm
– geometric limitations (the object/
sample may cover certain areas of
the detector, some higher d
hkl
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 specifc 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 5
th
-Century Carpathian Basin
50
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 frst 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 fuorescence spectrometry. No surface
cleaning was performed prior to the measurements, and we
tried to analyse the least corroded parts and as fat 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 mm
2
); 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
frst 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 afect
the imaging, the analysed area was thoroughly cleaned with
acetone or ethanol. Analyses of non-fat 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
fat 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
verifed with the use of micro-X-ray difractometry.
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 fuorescence spectrometry (hXRF)
A SPECTRO xSORT Combi handheld X-ray fuorescence
spectrometer was used. Analytical conditions: 15–50 kV,
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 energy-
dispersive 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, Al
2
O
3
, SiO
2
, wollastonite, Ti, Cr, Mn, Fe,
FeS
2
, 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 difractometry (µ-XRD)
A RIGAKU D/MAX RAPID II micro-X-ray difractometer
(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
difractometer was operated with CuK
α
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
difraction image from the laser readout. For each XRD
pattern, the interpretable 2Θ region was selected manually.
RIGAKU PDXL 1.8 integrated X-ray powder difraction
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 diferent parts (front-plate, loop, tongue, and back-
plate) of
buckle ZsD
(Figure 1A) were manufactured from
diferent 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
diferent parts. Buckle ZsD has the lowest zinc (0–0.6 wt%)
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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 5
th
-Century Carpathian Basin
51
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.
DescriptionAgCuAuPbBiSnZnAu/AgBi/PbHg
the buckle from Zsibót–Domolospuszta (buckle ZsD)
loop
87.48.4
2.11.2
0.07
< LOD
0.60.0250.06
–
tongue
90.9
5.9
1.80.90.06
< LOD
0.20.0200.06
–
back-plate95.42.9
1.00.40.06
< LOD< LOD
0.0110.15
–
front-plate
90.65.8
1.51.5
0.06
< LOD
0.60.0160.04
–
gilding19.9
0.978.8
< LOD< LOD< LOD
0.1
+
the buckle with unknown provenance (buckle UP)
loop
82.7
12.9
0.71.60.05
< LOD1.4
0.0090.03
–
front-plate
87.68.31.00.90.06
< LOD
1.70.0110.07
–
tongue with bird-head
87.07.3
1.2
1.60.05
< LOD
1.80.0130.03
–
tongue with bird- and boar-head
81.010.31.01.6
< LOD< LOD
4.00.013
–
gilding13.91.3
83.9
< LOD< LOD< LOD
0.2
+
the buckle from Bácsordas (buckle B/K)
front-plate91.1
5.70.7
1.2
0.05
< LOD1.2
0.0080.04
–
loop
89.95.70.7
2.5
0.04
< LOD1.1
0.0070.02
–
tongue
90.5
5.3
0.81.80.07
< LOD1.2
0.0080.04
–
gilding14.41.4
83.7
< LOD< LOD< LOD
0.1
+
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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 5
th
-Century Carpathian Basin
52
and highest gold content (1.0–2.1 wt%) among the buckles.
The diferent 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 diference between its parts in terms of lead
content: the loop has the highest (2.5 wt%), while the front-
plate has the lowest (1.2 wt%) lead content. The zinc content
is 1.1–1.2 wt%.
The diferent parts (front-plate, loop and tongues) of
buckle UP
(Figure 1C) were manufactured from diferent
low quality silver alloys (81.0–87.6 wt% Ag). The gold and
lead contents of its parts difer 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
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 diferent silver-copper sulphides
with diferent 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 fat, 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 silver-
copper 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 Ag-
Cu 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).
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 5
th
century AD is depicted for comparison (unpublished
data).
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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 5
th
-Century Carpathian Basin
53
Table 4.
Elemental composition of the niello inlays based on the SEM-EDX measurements. The results are given in wt% and at%.
Description
wt% →
AgCuSAuHg
at% →
AgCuSAuHg
the buckle from Zsibót-Domolospuszta (buckle ZsD)
front-plate
niello 1sp5lighter
72.113.014.870.621.67.8
niello 2sp1lighter
82.48.3
2.1
0.96.476.7
13.1
6.60.5
3.2
sp2darker
36.048.9
15.121.2
48.9
29.9
niello 3sp2lighter
70.76.60.8
21.9
73.311.6
2.912.2
sp4lighter
79.55.0
1.114.4
80.08.63.77.8
sp5lighter
78.69.7
1.99.9
73.7
15.45.9
5.0
niello 4sp2lighter
77.43.00.119.683.0
5.4
0.2
11.3
sp3lighter
77.87.61.812.875.0
12.45.9
6.7
loop
niello 4sp1lighter
50.833.715.631.735.732.7
sp2darker
5.074.520.5
2.5
63.1
34.5
sp3lightest
68.27.9
23.9
72.1
14.2
13.6
niello 5sp2darker2.5
76.620.9
1.3
64.234.6
sp3lightest
57.920.214.746.527.6
19.5
6.4
sp4lighter
50.734.0
15.3
31.736.1
32.2
niello 6
sp1darker13.5
66.6
19.9
7.058.534.6
niello 7
sp1darker12.9
68.97.2
1.2
6.962.330.50.3
sp2lighter44.5
39.7
15.3
0.527.2
41.231.5
0.2
niello 9sp2darker
56.830.612.737.5
34.3
28.2
sp3lighter
64.718.36.210.9
52.925.3
17.14.8
niello 10
sp1darker21.9
60.817.312.056.331.7
sp3lightest
62.8
24.912.342.9
28.928.2
sp4lighter
37.3
45.9
16.821.7
45.432.9
niello 13sp1darker
3.888.87.5
2.1
84.014.0
sp2lighter
50.230.410.48.9
35.4
36.424.8
3.4
sp3lighter
39.7
31.4
16.6
12.325.534.3
36.0
4.3
sp4lightest
67.19.6
2.4
65.4
15.9
7.811.0
niello 15sp1darkest
8.871.9
19.34.5
62.4
33.1
sp2darker
29.054.616.416.4
52.331.3
sp3lighter
48.4
31.1
9.611.034.837.9
23.14.2
tongue
niello 1sp3lighter
71.6
21.5
11.648.724.826.5
sp4darker59.921.5
10.945.027.427.6
sp5lighter
67.525.8
13.343.3
28.128.7
niello 3sp2darker
70.0
19.3
10.750.423.7
25.9
sp3lighter
98.6
1.4
97.6
2.4
sp4darker
74.516.4
9.1
56.021.023.0
sp5lighter
95.8
3.3
0.991.7
5.42.9
niello 5sp2lighter
98.7
1.1
0.297.6
1.9
0.6
sp3darker
57.627.2
15.2
37.229.833.0
sp4lighter
97.4
2.1
0.594.8
3.5
1.7
sp5darker
70.518.910.651.0
23.2
25.8
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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 5
th
-Century Carpathian Basin
54
Description
wt% →
AgCuSAuHg
at% →
AgCuSAuHg
the buckle with unknown provenance (buckle UP)
front-plate
niello 1sp3lighter
30.4
52.4
17.217.250.232.6
sp4darker
21.062.916.011.658.829.7
niello 2sp2darker
36.846.217.0
21.345.533.2
sp3lighter44.5
38.816.826.7
39.5
33.8
sp1lighter
60.429.89.742.0
35.2
22.8
sp2darker53.432.1
14.634.034.7
31.3
sp4lighter
50.936.113.032.6
39.3
28.1
sp5darker
13.668.717.77.261.5
31.3
sp1lighter
30.0
51.3
18.716.748.4
34.9
sp2lightest
71.97.1
2.1
10.98.070.912.07.1
5.94.2
sp3lighter41.342.2
16.6
24.542.433.1
sp5lighter
38.446.2
15.4
22.846.530.7
sp6
darker33.5
47.519.018.8
45.335.9
the buckle from Bácsordas (buckle B/K)
plate
niello 3sp1darker
27.753.818.4
15.3
50.5
34.2
sp3lighter
82.8
12.1
5.068.817.1
14.1
sp1lighter
50.336.6
13.232.1
39.728.3
sp2lightest94.93.91.2
89.96.2
3.9
sp4darker
45.638.316.127.7
39.432.9
niello 4sp1darker39.1
46.114.8
23.4
46.829.8
sp2darker35.2
50.3
14.5
20.850.428.8
sp3lighter
62.926.610.5
43.931.5
24.6
sp3lightest
97.32.7
95.4
4.6
sp4darker
18.962.618.510.156.7
33.2
sp5lighter
38.7
49.911.423.952.3
23.8
niello 5sp1lighter
87.8
9.23.1
77.213.79.0
sp2darker
40.8
43.4
15.8
24.3
44.031.7
sp3darkest
16.369.114.78.964.127.0
niello 4sp1darker39.3
46.4
14.3
23.747.429.0
sp2lighter
93.74.61.787.47.3
5.3
sp1darker
57.529.712.738.2
33.5
28.4
sp2lighter
80.113.66.364.418.517.0
niello 6
sp1lighter
78.6
14.3
7.162.0
19.2
18.8
sp3darker
37.247.815.022.048.1
29.9
sp1lighter
93.6
4.4
2.086.76.96.4
sp2darker19.1
62.918.010.357.3
32.5
sp4darker29.3
58.6
12.1
17.358.724.0
sp5lighter39.9
46.313.8
24.2
47.628.2
Table 4.
Elemental composition of the niello inlays based on the SEM-EDX measurements. The results are given in wt% and at%. (
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 5
th
-Century Carpathian Basin
55
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 identifed 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 high-
grade 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
fne, wavy rays of fuid inclusions accompanied by ilmenite
plates (Figure 9C–D). Another specifc 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
The results of the µ-XRD measurements proved the
presence of stromeyerite (AgCuS), digenite (Cu
9
S
5
)
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 (Ag
3
CuS
4
) and acanthite
(Ag
2
S) (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 fgures, they are contrasting with the colours of
precious metals and niello (Figure 3). The prevailing shape
of the garnet slabs is fat and round, although some triangular,
rectangular, lunula- and drop-shaped pieces are also present.
Figure 5.
Composition of the niello inlays of the buckles based on SEM-EDX measurements. Chemical ranges for diferent silver-copper sulphides are
based on Grybeck and Finney (1968) for jalpaite (Ag
1.55
Cu
0.45
S-Ag
1.5
Cu
0.5
S); Skinner
et al.
(1966) and Kolitsch (2010) for mckinstryite (Ag
1.18
Cu
0.82
S-
Ag
1.25
Cu
0.75
S), and Frueh (1955) and Tokuhara
et al.
(2009) for stromeyerite (Ag
0.9
Cu
1.1
S-Ag
1.0
Cu
1.0
S), respectively.
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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 5
th
-Century Carpathian Basin
56