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Micro-Raman on Roman glass mosaic tesseraeInvernizzi C.1,2, Basso E.1,3,Malagodi M.1,4,Bersani D.2, Lottici P.P.2, La Russa M.F.5
1Laboratorio Arvedi, CISRiC, Universit degli Studi di Pavia, via Ferrata 1, Pavia 27100, Italy2Dipartimento di Fisica e Scienze della Terra, Universit degli Studi di Parma, Parco Areas delle Scienze 7/a, 43100 Parma, It
3Dipartimento di Scienze della Terra e dellAmbiente, Universit degli Studi di Pavia, via Ferrata 1, Pavia 27100, Italy4Dipartimento di Chimica, Universit degli Studi di Pavia, via Taramelli 12, 27100 Pavia, Italy
5Dipartimento di Scienze della Terra, Universit della Calabria, via Bucci, Arcavacata di Rende (CS) 87036, Italy
ntroduction
he Villadei Quintili(1) was the biggest and magnificent estate of the Roman suburbia, set along the Via Appia Antica. The original nuc
uring the Age of Traiano-Adriano (first half of the second century A.D.) by the rich family of Quintili and it was widened when Comecome an imperial property, enriching it of functional facilities and decorations. The central area (2) includes different spaces:
uilding/ludus, the areas of private residence and representation, the arcaded gardens and the thermal baths (frigidarium, tepidarium an
he archeological excavations have unearthed a lot of materials: ceramic and vitreous artifacts, marbles, mosaics, mural paintings ecc
undreds of glass mosaic tesserae were retrieved in the thermal baths, where they probably decorated the vaults.
bject of this study are twenty-one glass mosaic tesserae (5), mostly opaque and covering the majority of colour palette of that time, co
alidarium (3,4) under the supervision of the Soprintendenza Speciale dei Beni Archeologici (Rome). The aim of the detailed s
icrostructural and chemical characterization of both the glass matrix and the crystalline inclusions was to identify the raw materials,
gents and the opacifiers as well as the production technology used during the Roman Imperial Age.
Analytical t
-Raman
FESEM-ED
LA-ICP-MS
XRPD
Glass matrix
) Soda-lime-silica glass natron as flux
) Lead-alkali mixed composition glass
plant-ash as flux
natron-plant ash as flux
olouring and opacifying agents
onclusions
he majority of the tesserae show the characteristic composition of the natron glass, typical of Imperial age. As vitrifying agent a coast
sed, high-purity oxide stabilizers (CaO) being present in the sand for the phenomena of bio-accumulation of marine organisms. The red
sserae represent two outliers, because of their lead-alkali mixed composition: for the red glass plant ash was likely used as flux, whi
ass displays an intermediate composition between natron and plant ash glass.
he colour and the opacity were obtained by the combination of chromophore ions and/or opacifying and colouring crystals: Pb-Sn
ellow), Ca-antimonates (white), a mixture of Sn-Pb antimonates and Cu2+ions (emerald green), a mixture of Ca antimonates and Co2+(
ue) or Cu2+(blue-green) ions, Cu0 metal nanoparticles (red) and Cu2O sub-micron crystals (orange).
Vitrifying agent Flux agent Stabilizing agentRe
co
Sr
the
ba
Ca
de
ac
org
sa4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
300 400 500 600 700 800 900
Sr ppm
CaOwt%
orange
light blue
white
blue
yellow
colourless
red
green
5
Pb-Sn antimonates
(SO4)2- group of
Nosean mineral
Na8Al6Si6O24(SO4)
(dark area in BSE
image) formed by
the reaction between
raw materials used to
make the opacifier
and gangue minerals
Ca antimonates
Cuprite
(SO4)2-
etallic copper
u0 nanocrystals
mogeneously
spersed in
ass matrix
SE image)
Chromophore ions
Cu2O sub-micron crystals
Homogeneously dispersed
in glass matrix (BSE image)
Ion Glass colour Concentration
Co2+Blue
(purplish hue)
285-599 ppm
122-191 ppm
Cu2+
Blue
(greenish
hue)
1-3.1 wt% (CuO
1628 ppm
0.0
5.0
10.0
15.0
20.0
25.0
30.0
30 35 40 45 50 55 60 65 70 75
SiO2wt%
PbOwt%
orange
light blue
white
blue
yellow
colourless
red
green
PbO contents are
related to
colouring/opacifying
agent (Pb-Sn
antimonate)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0
K2O wt%
MgOwt%
orange
light blue
white
blue
yellow
colourless
red
green
Plant ash-based glass
Natron-based glass
Mixed natron-plant ash based glass
(Andreescu -Treadgold and Henderson
2006)
13
4
Ca2Sb2O7
CaSb2O6
Pb2Sb2-xSnxO7-x/2
