Scholarly article on topic '‘A green thought in a green shade’; Compositional and typological observations concerning the production of emerald green glass vessels in the 1st century A.D.'

‘A green thought in a green shade’; Compositional and typological observations concerning the production of emerald green glass vessels in the 1st century A.D. Academic research paper on "History and archaeology"

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{"Roman glass" / "Plant ash" / "First century AD" / "Emerald green glass" / "Trace elements" / "Compositional analysis" / "Vessel forms"}

Abstract of research paper on History and archaeology, author of scientific article — Caroline M. Jackson, Sally Cottam

Abstract The results of a programme of compositional analysis on a series of emerald green glass vessels of known form and date suggest that emerald green vessels have distinct characteristics that set them apart from most contemporary glasses. These specific compositional peculiarities presented here will be evaluated in the context of the varieties of vessel forms produced in the colour. In the light of our findings we will suggest a number of ways forward in the understanding of the structure of the early Roman glass industry.

Academic research paper on topic "‘A green thought in a green shade’; Compositional and typological observations concerning the production of emerald green glass vessels in the 1st century A.D."

Accepted Manuscript

'A green thought in a green shade'; Compositional and typological observations

concerning the production of emerald green glass vessels in the 1 century A.D. Caroline M. Jackson, Sally Cottam

PII: S0305-4403(15)00166-1

DOI: 10.1016/j.jas.2015.05.004

Reference: YJASC 4429

To appear in: Journal of Archaeological Science

Received Date: 30 January 2015 Revised Date: 8 May 2015 Accepted Date: 14 May 2015

Please cite this article as: Jackson, C.M, Cottam, S., 'A green thought in a green shade'; Compositional

and typological observations concerning the production of emerald green glass vessels in the 1 century A.D., Journal of Archaeological Science (2015), doi: 10.1016/j.jas.2015.05.004.

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1 'A green thought in a green shade'; Compositional and typological observations

2 concerning the production of emerald green glass vessels in the 1st century A.D.

4 Caroline M Jackson1 and Sally Cottam2

5 department of Archaeology, University of Sheffield, Northgate House, West Street, Sheffield,

6 S1 4ET, U.K. c.m.jackson@sheffield.ac.uk

7 ^Department of Classics, King's College London, Strand, London, WC2R 2LS, U.K.

8 sally.cottam@kcl.ac.uk

10 Abstract

11 The results of a programme of compositional analysis on a series of emerald green glass vessels

12 of known form and date suggest that emerald green vessels have distinct characteristics that set

13 them apart from most contemporary glasses. These specific compositional peculiarities presented

14 here will be evaluated in the context of the varieties of vessel forms produced in the colour. In

15 the light of our findings we will suggest a number of ways forward in the understanding of the

16 structure of the early Roman glass industry.

17 Highlights

18 • Early Roman emerald green glass has a basic composition that differs from that of other

19 mainstream colours which suggests it was coloured during primary production.

21 • In the repertoire of common 1st century A.D. forms, emerald green is not used for certain

22 vessel types, raising questions of supply to secondary workshops.

24 • Specific vessel forms (e.g. Isings 12) have higher concentrations of lead, which suggests

25 a potential link to the early Roman high lead antimony colourless glasses in terms of

26 production.

28 • The alkali raw materials used to produce this glass are difficult to determine. It may be

29 produced using low potash soda ashes or a mixture of ashes, or perhaps a combination of

30 ash and natron.

32 • The trace elements show a complex pattern which is highly influenced by the impurities

33 in the colorant. However, the origin of the glass appears to be Egyptian.

35 • Early Roman emerald green glass is made with a base glass which is higher in magnesia,

36 potash and phosphorus which seems to be advantageous to colour formation.

38 1. Introduction

39 The first three quarters of the 1st century A.D. witnessed by far the most widespread and

40 adventurous use of brightly coloured glass in the history of glassmaking in the ancient world.

41 The range of colours and the variety of forms in use across the Roman Empire are unrivalled

42 until the modern period. Whilst vessels in the bluish-green shades of naturally coloured glass

43 were at all times by far the most common, a vast palette of other colours was available and

44 enthusiastically exploited. Most of these brightly coloured vessels were monochrome, but 1st

45 century glassworkers also took advantage of the contrasts of coloured glass by creating complex

46 polychrome vessels. Translucent dark blues, ambers, purples and emerald greens are the most

47 common bright colours used during this time. Less common are opaque colours such as whites,

48 reds, yellows, pale blues and glasses so dark as to appear black.

50 Although many hundreds of thousands of fragments of glass from 1st century excavations have

51 been examined, there is still only a rudimentary understanding of the organisation of the industry

52 producing these remarkable vessels. In this paper, we present the preliminary results of a project

53 that takes an important new methodological approach to the problem. Our research combines an

54 in-depth understanding of the typological and chronological patterns regarding early Imperial

55 vessel forms and manufacturing techniques, in conjunction with the results of compositional

56 analysis of a single colour of early Roman glass, emerald green. We propose that this

57 combination of expertise is crucial to the understanding of the processes involved in glass

58 production during this most fascinating period in the evolution of the Roman glass industry.

60 1.2 Background

61 Emerald green is a familiar colour to glass specialists working with assemblages of the early -

62 mid 1st century A.D. Production appears to peak in the decades leading up to the mid 1st century

63 A.D., and the colour becomes much less common in the second half of the century, although a

64 few vessels seem to have been produced after this point (Price and Cottam 1998, 55-59). This

65 glass was used to produce a wide range of vessels, both monochrome and, occasionally,

66 polychrome. The colour was not restricted to any particular production method and was used in

67 the three principal techniques of vessel manufacture - non-blown (cast), free-blown and mould-

68 blown. However, a closer typological analysis reveals that in the early and mid 1st century A.D.,

69 when the use of this colour was at its height, emerald green is strikingly absent in the

70 manufacture of some very common vessel forms. This was remarked upon by David Grose

71 (1991, 2-11) when he surveyed early Roman glasses from Italy. Emerald green, he proposed,

72 was essentially a Roman colour and not part of the Hellenistic glass vessel-making industry

73 (Grose 1991, 8). He noted that some commonly found Augustan-Flavian monochrome non-

74 blown forms were not produced in emerald green glass. These included ribbed bowls (fig 1.1;

75 Isings 1957 form 3), as well as 'linear-cut' bowls (fig. 1.2). Conversely, he observed that emerald

76 green was a particularly favoured colour for producing the range of non-blown vessels often

77 described as 'fine wares' or 'ceramic forms' (Grose 1991, 2, fig. 1 pl.I, IIa, IIIb). This category

78 includes cups and bowls with a constricted convex profile (figs.1.4 and 1.5; Isings 1957 form 2)

79 bowls with vertical sides (fig. 1.6 and 1.7; Isings 1957 form 22) and convex sided cups and bowls

80 on a narrow base ring (fig. 1. 8 and 1.9; Isings 1957 forms 5 and 20). Convex bowls with no base

81 ring and shallow flat-based bowls form a further group of non-blown bowls which are often

82 produced in emerald green (fig. 1.10, 1.11 and 1.12; Isings 1957 forms 18 and 19).

85 In our survey of the 1st century A.D. vessel forms produced in emerald green glass, we have also

86 found that the peculiarities in the use of emerald green observed by Grose (1991) can also be

87 found amongst certain contemporary blown forms. For example, the distinctive blown ribbed

88 bowl, often decorated with opaque white trails (fig.1.3; Isings 1957 form 17), does not occur in

89 emerald green, though amber, purple, dark blue, pale green and blue/green are all regularly

90 noted. The many forms of jug produced during the 1st century are very uncommon in emerald

91 green glass. Furthermore, emerald green is rarely used as a base colour for blown vessels

92 decorated with contrasting trails or splashes, whilst amber, purple and dark blue are quite

93 frequently used in this way.

95 The composition of emerald green is also atypical. Henderson (1996, 190) first noted that five

96 1st-century A.D. non-blown (cast) emerald green cups and bowls from the palace at Fishbourne

97 (West Sussex), were compositionally unlike other contemporary Roman glasses. These green

98 glasses were soda-lime-silica, but with potassium and magnesium above 1.5wt%, more typical of

99 glasses produced using a plant-ash flux rather than a mineral soda (trona or 'natron'). They were

100 coloured with copper, with higher concentrations of iron, tin and sometimes lead, which

101 Henderson (1996, 190) attributed to the use of scrap bronze.

103 More recent analyses of early Roman emerald green vessel glasses show the same compositional

104 traits (Colchester (Jackson et al. 2009), Adria region (Gallo et al. 2013), Begram (Brill 1999,

105 125, sample 6226), Golfe de Fos, Ruscino (Thirion-Merle 2005) and in green glass in 2nd century

106 polychrome vessels from Chester (Paynter and Schibille in press)). Furthermore, although

107 predominantly found in emerald green, some 'copper' red glass has these compositional

108 characteristics (Moretti and Gratuze 2000, Nenna and Gratuze 2009, Paynter and Kearns 2011,

109 Gallo et al. 2013). Very occasionally other early examples in green, brown, black and dark blue,

110 not coloured with copper, exhibit this composition (Gallo et al. 2013, Thirion-Merle 2005, van

111 der Linden et al. 2009 and later 4th century examples from Egypt in Rosenow and Rehren

112 2014). However, whilst this ash-based composition is not exclusively reserved for green, early

113 Roman emerald green comprises by far the largest group consistently produced using some plant

114 ash flux.

116 1.3 Aims

117 As part of a project to explore these typological and compositional patterns further, a set of 50

118 emerald green vessels of known form was analysed from early to mid-1st-century sites at Frejus

119 and Barzan in France, Colchester in England and Ribnica and Trojane in Slovenia. The

120 examples selected consisted of vessels of several different types, manufactured using non-blown

121 (cast), mould-blown and blown techniques, to determine whether the unusual composition was

122 used only for specific vessel forms. The forms include:

124 25 samples from non-blown (cast) forms (vessel forms are included in Table 1)

125 • Cups with constricted convex sides (fig. 1.4, 1.5 and 2.1; Isings form 2)

126 • Small cylindrical bowls (fig. 1.6, 1.7 and 2.2; Isings form 22)

127 • Small bowls with an out-turned rim (fig. 1.13)

128 • Convex sided bowls with base rings (fig. 1.8, 1.9 and fig.2.3; Isings form 5 and 20)

129 • Convex sided bowls without base rings (fig. 1.10 and 1.11; Isings form 18)

130 • Shallow flat based bowls (fig. 1.12, fig.2.4; Isings form 19)

131 2 samples from mould-blown forms

132 • Circus cup (fig. 1.14)

133 • Ribbed cup (fig. 1.15)

134 23 samples from blown forms

135 • Convex cups (fig. 1.16; Isings form 12)

136 • Shallow tubular rimmed bowls (fig.2.5; Isings form 45)

137 • Bowls with flared rims (fig.2.6)

138 • Bowls with out-turned rims (fig.2.7)

140 Other published compositional data from emerald green glasses, such as the data from

141 Fishbourne, various sites in France and Adria, were also used to extend the dataset.

143 2. Methods

144 Major and minor elements were measured using an electron microprobe. The samples from

145 Frejus and Colchester were analysed using a Cambridge Microscan 9 at the Department of Earth

146 Sciences at Sheffield University. Operating parameters, counting times and analytical protocol

147 are given in Lemke (1998, 281-3). The remaining samples were analysed with a JEOL JXA-

148 8200 electron microprobe housed in the Microanalysis Research Facility, at the Department of

149 Archaeology, Nottingham University (see Meek et al., 2012, 790 for operating parameters). In

150 both analytical sessions a Corning B soda-lime-silica glass standard was run throughout to check

151 for accuracy and precision and to monitor any drift. The average results are presented in Table 2

152 and the data show good agreement with the standard data for most elements, except for antimony

153 oxide on the Sheffield EPMA and titania at Nottingham; these elements must therefore be

154 considered semi-quantitative.

156 Trace element analysis was performed using a CETAC LSX-100 laser ablation system in

157 conjunction with an Agilent 7500c ICP-MS instrument at Imperial College, Ascot. Instrument

158 running parameters and standard data are documented in Jackson and Nicholson (2010). Repeat

159 measurements of SRM NIST 612 were made to assess the data (Table 3) which generally was

160 within 10% of the standards.

162 3. Results of the compositional analysis

163 All the glasses are of a soda-lime-silica composition (Appendix 1). Soda concentrations average

164 around 16.5wt%, lime around 6.5-7 wt%, and alumina is typically around 2.5wt%. Potash,

165 magnesia and phosphorus pentoxide are higher than in Roman natron glasses (average 1.7wt%,

166 2.0wt% and 0.7wt% respectively). Lilyquist and Brill (1993) suggest concentrations of

167 magnesia and potash above 1.5 wt% indicate manufacture using plant ash rather than solely

168 natron. This is also reflected in the lower silica concentrations than typical Roman natron

169 glasses, which is a consequence of the need to add greater quantities of plant ash to introduce

170 enough alkali in order to flux the silica.

172 It is more difficult to determine which elements derived from which raw material in glasses

173 produced with plant ash fluxes as they are much more complex compositionally than mineral

174 soda fluxes such as natron. Plant ashes are also more variable and their compositions change

175 according to the substrate on which they grow and how they concentrate specific elements into

176 their tissues. Taking these issues into account, the data are described and interpreted tentatively

177 in terms of the contribution of both plant ashes and sand to the glass composition.

179 Within this general 'plant ash' composition there is some variation between samples. For

180 instance four 'peacock' coloured samples have an intermediate composition between natron and

181 plant ash glasses (S757 and S1296 from Ribnica and Frejus 156 and 158, including blown and

182 non-blown forms). These samples contain only slightly higher concentrations of potash than a

183 natron glass, up to 1wt% MgO, and very low P2O5 concentrations. This may suggest the mixing

184 of natron and plant ashes or of their respective glasses through recycling (Paynter 2008,

185 Freestone and Stapleton forthcoming).

187 The concentrations of lime in emerald green glasses are worthy of comment. Calcium in glasses

188 can derive from various sources. All plant ashes typically contain a high proportion of calcium

189 compounds (Barkoudah and Henderson 2006, Turner 1956, Jackson et al. 2005), similarly the

190 sand used to make natron glass contained calcium, derived from shells (e.g. Brems et al 2012).

191 If these glasses were made with plant-ash and the same sands used to manufacture Roman

192 mineral-soda glasses, a high lime composition would have resulted, as both the sand and the ash

193 would have contributed lime to the batch (Brill 1999, 483). However, the plant-ash emerald

194 green glasses here display similar, or slightly lower, concentrations of lime to the mineral-soda

195 glasses from the same sites (unpublished data) and other mineral-soda 1st-century glasses

196 (Jackson et al. 2009, Gallo et al. 2013). This may suggest the emerald green glass was produced

197 with either a different (low-lime) sand source, crushed quartz or that the plant ash used was

198 particularly low in calcium. A low lime content is also seen in high antimony Egyptian

199 colourless natron glasses of the 1st century (Jackson and Paynter 2015, Gallo et al. 2013) which

200 were also produced using high quality silica sources, and has been observed in opaque red

201 glasses (unpublished data).

203 All the glasses contain copper at high concentrations, often over 2wt%. Copper in glasses in the

204 Cu2+ state can be either blue or green, but here the colour probably depends upon interactions of

205 copper and iron (>1wt%), and to some extent manganese (>1wt%), antimony, tin, lead and the

206 base glass composition which will influence the redox states of the colouring elements (Weyl

207 1953, 164). The concentrations of all these elements in the glass suggest deliberate addition.

209 Antimony is present in all the glasses, up to 0.5wt%, which may indicate it has some influence

210 on colour generation. Tin is also found in some samples and may be a feature of the addition of

211 bronze. Lead, at low concentrations, may relate to the addition of copper as bronze, although in

212 colourless glasses of the 1st century A.D. it can be linked to the addition of antimony (Paynter

213 2006, Jackson and Paynter 2015).

215 4. Discussion

216 That the glassmakers producing these glasses had a sophisticated understanding of the colouring

217 technology and behaviour of differing additives to the glass is evident in the consistency and

218 brilliance of the emerald green glass achieved. However the deliberate and consistent use of a

219 plant-ash flux in the production of these vessels needs to be explained. The most obvious

220 question is whether the use of a plant-ash alkali enabled the glassmaker to more easily achieve

221 the emerald green colour produced by copper and iron, a colour which might perhaps not be

222 readily produced in natron-based glasses. A further point that arises is whether this glass

223 production technology relates to a distinct method of glass production and even a particular

224 location of production It is possible for example that the colour could only be created by

225 particular glassmakers, with skilled knowledge, and potentially even a monopoly on emerald

226 green production. These questions are explored further below.

228 4.1 Raw Materials and their sources

229 Plant ashes have been shown to vary between different species and within species from different

230 locations (Barkoudah and Henderson 2006). Differences in alkalis within the analytical group

231 may therefore indicate different glassmaking centres. Phosphorus pentoxide and magnesia, and

232 potash and magnesia, are strongly correlated in these glasses which suggests that the green

233 samples analysed here as well as those from other datasets (Gallo et al 2013, Henderson 1996,

234 Thirion-Merle 2005) form a single compositional group (fig. 3), using the same alkali type (and

235 possibly source). The lack of a clear correlation between soda with potash, magnesia or

236 phosphorus and the variable concentration of soda (15-19wt%) may also suggest a

237 supplementary source of soda (natron?) was added to some of the glasses, or potentially that

238 natron glass was being extended or mixed with a plant ash which was high in phosphorus. The

239 occurrence of samples with low soda (<17wt%) and alumina (<1.8wt%) noted by Thirion-

240 Merle (2005) and Gallo et al. (2013, 2597), which they suggest indicates the use of a pure silica

241 sand, is seen in only some, but not all the emerald green glasses here.

243 The ratios of phosphorus pentoxide and magnesia differ from soda-ash glasses from other

244 regions and periods (fig. 3); Late Bronze Age Egyptian, and first millennium A.D. Sasanian and

245 Islamic plant-ash glasses tend to have lower phosphorus pentoxide, higher magnesia and differ in

246 their soda and potash to the Roman emerald green samples (Mirti et al. 2008, Shortland 2008,

247 Freestone et al. 2000). The concentration of phosphorus pentoxide in particular is often higher

248 in the emerald green glass than would be expected from that contributed by plant ashes, such as

249 the Salicornia or other high-soda plants analysed by Brill (1999, 482-484) and Barkoudah and

250 Henderson (2006). None of these earlier or later glasses provide a suitable comparative

251 compositional group so there seems to be no obvious evidence to suggest a common provenance.

253 4.2 Trace elements

254 Trace elements and rare earth elements (REE) are used to determine a general provenance of the

255 raw materials used in glass manufacture. In plant-ash glasses it might be expected that both the

256 sand, or ground quartz, and ashes will contribute to the overall compositional make-up of the

257 glass (Ichihashi et al., 1992, Barkoudah and Henderson 2006). Certain trace elements are

258 thought to be associated with silica sources. Brems and Degryse (2013) note that in Roman

259 natron glasses Ti, Cr, Sr, Zr and Ba are the most diagnostic to determine the nature of the silica

260 source used.

262 The measured trace element concentrations in the emerald green glass are given in Appendix 2.

263 Figure 4 plots raw Roman natron glasses from Apollonia (Freestone et al 2000) and a selection

264 of our emerald green glasses. The Apollonia glass has been chosen here as it represents a glass

265 produced with a typical sand available at a primary production site in the western Mediterranean

266 coastal region and is described in documentary sources of the 1st century AD (e.g. Pliny NH

267 XXXVI and Strabo Geography 16.2.25). All show a distinctive pattern suggesting a similar

268 provenance, around the eastern Mediterranean. The high Sr peak is typical of sands from the

269 Syro-Palestinian and neighbouring regions. Only one potential sand from Italy shows a similar

270 trace element pattern (IT87, Brems and Degryse 2014), although slight differences in Nd and Dy

271 may rule out this particular source. This trace element pattern is similar for both blown and non-

272 blown forms.

274 The continuation of plant ash glass production in Mesopotamia in the Roman period (Sayre and

275 Smith 1961, Mirti et al. 2008), when natron glass dominated elsewhere in the Near East, has led

276 some authors to suggest a possible link between Roman emerald green glass and the

277 Mesopotamia region (e.g. Lemke 1998). Comparing the trace element ratios of chromium (Cr)

278 and lanthanum (La) measured in Bronze Age glasses from Mesopotamia and Egypt (fig. 5) and

279 the glasses studied here it can be seen that the early Roman emerald green glasses have La and

280 Cr concentrations in the same ratio as the Egyptian glasses, but are slightly higher. These ratios

281 are attributed predominantly to different silica sources (Shortland et al 2007, 788). The higher

282 concentrations of both in the Roman glasses may indicate more impure sand was used in

283 manufacture and/or they derive from additives (see below). The cautious interpretation is that on

284 this basis, the emerald green Roman glasses are more likely to have been manufactured in or

285 around Egypt or along the Mediterranean coast, rather than inland Mesopotamia. However, this

286 hypothesis must remain tentative unless more substantial evidence can be provided.

288 Further examination of the pattern of trace elements Ti, Cr, Sr and Zr shows that a positive

289 correlation as might be expected if they derive from the sand, however there are broad

290 correlations between Cu, Zr and Cr as well as groupings according to the lead levels, discussed

291 later. Likewise, other trace element suites can be related to the use of organic alkali source, such

292 as Li, Cs, K and Rb. However, the potential mixing of alkalis has been suggested earlier, and so

293 correlations between diagnostic trace elements and alkalis such as soda or potash are not clear,

294 and other broad correlations between Rb and Pb can be observed. This suggests that the most

295 significant variations observed in the trace elements may be related to the introduction of the

296 colourants, so whilst it is tempting to try and attribute the fluctuations seen in the trace elements

297 to either the flux or silica source, as with types of colourless glass, the situation with these deeply

298 coloured glasses is actually more complex.

300 4.3 Factors influencing colour

301 Emerald green is primarily produced by the presence of copper and iron in the glass. Although

302 the production of blues or greens in copper or iron-containing glasses is not difficult, the

303 behaviour of both together in silicate melts is complex.

305 Under oxidising conditions cupric (Cu2+) ions produce colours of different coordination; these

306 include blue and green. The colour is influenced by the state of solvation of the ion which is in

307 turn influenced by the concentration of that ion, the composition of the base glass and the

308 melting temperature (Weyl 1951, 159). For example although still in the cupric form, a blue

309 copper coloured glass will change to green upon heating as the number of unsaturated ions

310 increases. Thus with all other factors the same, copper glasses melted at low temperatures are

311 blue, whereas the same glasses melted at higher temperatures are greenish.

313 Iron may act as a reducing agent on copper, itself being oxidised. Under reducing conditions the

314 ferrous ion, Fe2+ produces a light blue colour. The ferric ion, Fe3+, produces a much less

315 intense yellow colour (approximately 1/10 the strength of the blue ferrous ion). Therefore when

316 iron is present, as it is here at concentrations above 1wt%, both oxidation states exist, changing

317 the colour from blue to green. The oxidation state of iron and the equilibrium between

318 Fe2+/Fe3+, is also influenced by the base glass composition and melting temperature, affecting

319 the glass colour. The presence of iron with copper in a glass matrix will therefore help to

320 produce the green colour.

322 However, the production of a glass with two colouring agents is not sufficient to produce the hue

323 observed; other elements were deliberately introduced to produce the desired colour. Lead,

324 antimony, tin, chlorine or even carbon monoxide in the form of charcoal causes the formation of

325 more cuprous copper (Cu2+), moving the colour from blue to green (Weyl 1951, 162).

326 Replacing the alkali by calcium or magnesium has a similar effect, and Weyl (1951) suggests

327 that magnesia-containing glasses provide the most suitable bases for green transmission.

329 Therefore the use of a plant ash, higher in magnesium, lime and potassium than natron, along

330 with the presence of small amounts of charcoal in the ash would favour the formation of the

331 green colour. The presence of small amounts of lead, antimony and tin would also favour a

332 green glass as would iron in its oxidised state, itself reducing some of the copper. Taken

333 together it may be suggested that a plant-ash glass would more readily favour the production of

334 an emerald green colour than a mineral-soda glass.

336 Preliminary experiments to produce emerald green glass in both natron and plant-ash glasses,

337 using laboratory reagents and neutral/slightly oxidising atmospheres and different temperatures

338 have, however, been inconclusive and unsuccessful; a turquoise glass was formed in both base

339 glasses, which was only slightly more green in the plant ash glass. It is also worth noting here

340 that other findings suggest that this colour could be produced successfully using this combination

341 of copper and iron in a mineral-soda glass. The examples include some 1st-century A.D. glasses,

342 in particular 'natron' beads (Bertini et al. 2011, Arletti et al, 2010) and emerald green raw glass

343 (Robin 2008, 43), as well as two green glasses here which showed compositions suggesting a

344 mixture of alkalis was used, producing reduced potash and magnesia concentrations (S757,

345 S1296).

347 Therefore the use of plant ash would facilitate the production of the green hue, but it may not be

348 the only reason why it was used. The difficulty of producing the emerald colour experimentally

349 and the paucity of examples of natron emerald green glasses may indicate that production was

350 specialised, perhaps restricted to specific places or specific glassmakers.

353 4.4 Compositional patterns related to style

354 There were no significant compositional differences between non-blown and blown vessels.

355 However, one group of blown vessels, consisting of Isings form 12 blown cups and two mould-

356 blown cups, contain small, but significant, concentrations of lead (0.3-0.6wt%) (fig. 6). The

357 Isings form 12 cups are the most numerous single vessel form analysed and most come from

358 Barzan (7/12), as do both the mould-blown vessels. The other examples are from Frejus (2) and

359 Colchester (3). Although all these vessels are blown or mould-blown forms, lead is not a

360 specific feature, at least to blown vessels, as many others from a range of different vessel forms

361 have lower lead concentrations (although higher than would be expected naturally). In these

362 vessels there seems to be no specific typological or chronological patterning in lead content.

364 The higher lead concentration in these examples is intriguing and not easily explained.

365 Recycling cannot be discounted, but the presence of lead at up to 0.5wt% would suggest it was

366 deliberately added or that the glass was deliberately mixed with other lead-containing glasses to

367 either aid working (making the glass 'softer') or the production of the colour (lead can act as a

368 clarifier). However, neither of these enhancements seems particularly relevant to the vessel

369 forms in question, and would benefit any of the forms in the sample range. An alternative

370 suggestion is that they are a result of a failed red glass (Paynter and Kearns 2011) which also

371 contains high copper, iron and lead and can be of a 'soda-ash' composition. However it is

372 unlikely here as a) red glasses generally contain much higher ratios of lead to copper (see Moretti

373 and Gratuze 2000) and the reverse is true here, and b) red is much less common than emerald

374 green glass and it is unlikely so much glass failed in production.

376 A possible explanation may be advanced by comparison with other contemporary vessels.

377 Similar concentrations of lead have been observed in some higher status Hellenistic and early

378 Roman colourless glasses (Baxter et al., 2005, Paynter 2006), and attributed to the use of an

379 antimony-lead decolorizer. Interestingly, the two elements are also correlated in the emerald

380 green glasses (fig. 6). Similarly, both the high antimony colourless and the emerald green

381 glasses have low concentrations of lime (and some with low alumina) which may indicate a

382 common provenance/tradition.

384 4.5 Provenance and the organisation of production

385 It is now comparatively well accepted that Roman glasses were manufactured in large centres

386 located around the eastern Mediterranean and that glass was traded as blocks to many secondary

387 centres as Pliny intimates (Pliny NH XXXVI, 190-194, Foster and Jackson 2009). The

388 analytical basis for this model rests on the compositional homogeneity of Roman natron glasses

389 which show few distinct compositional groups, and upon isotope and trace element analysis

390 which gives a likely provenance for glass manufacture. For plant-ash glasses equally a tight

391 compositional grouping would suggest a common origin; more than one distinct grouping might

392 indicate a number of different production centres, each using slightly different raw materials.

393 The likely provenance of the glasses is more difficult to ascertain, but as we have seen trace

394 element data indicate, using our present understanding of the geology of the Mediterranean, that

395 the sands used to produce these glasses have common characteristics to those from the eastern

396 Mediterranean, possibly in or near to Egypt.

398 Moreover, the relationship between emerald green and the plant-ash recipe makes it clear that

399 colouring took place at the primary manufacturing location. A plant-ash based industry not

400 linked to colour would surely reveal itself in the regular identification of this composition in

401 vessels of other colours. However, whether colour production is the only explanation for the use

402 of plant-ash glass certainly needs to be considered, and it may be that other factors, perhaps

403 linked to customs of manufacture within the primary glass-making industry, also played a role.

405 Evidence of 1st century A.D. primary glass production is extremely scarce (Nenna in press) and it

406 is at this stage difficult to establish whether the industry was centralised in a limited number of

407 locations, or more dispersed in character; although the differences in lead concentrations may

408 indicate more than one production location. Similarly, it is not clear whether the production of

409 emerald green glass was integrated within the larger mineral-soda glass industries, or was a

410 separate, perhaps specialised, enterprise. The similarity of the raw materials used to produce

411 plant-ash and colourless mineral-soda Roman glasses, certainly in terms of the (low lime) quartz

412 sands, might indicate that emerald green glass production was not an entirely distinct, separately

413 located industry.

415 On the other hand, an examination of how emerald green glass was used in the secondary stage

416 of the industry, vessel production, does raise questions about whether the relationship between

417 the two glass-making methods was as close as the analytical evidence suggests, because emerald

418 green was only used for certain forms. One of the first points to address is whether emerald

419 green was deliberately avoided in the production of some vessel forms because of certain

420 physical properties that made the glass harder to fashion into particular forms. However, there is

421 no evidence at this point that this is the case or that features such as ribs or handles are more

422 difficult to form in emerald green glass than in other colours. Cultural or aesthetic concerns

423 whilst possible, seem unlikely and are beyond the remit of this paper.

425 These discrepancies can now be re-examined in the light of the analytical results. If certain

426 common 1st century vessel forms, such as monochrome ribbed bowls of Isings form 3, or blown

427 ribbed bowls of Isings form 17, are not being produced in emerald green glass, and no

428 technological reason can be provided, then a possible explanation lies in the supply or use of this

429 particular colour to the secondary workshops where these particular forms were being made. If

430 this explanation is accepted, then the implications for the organisation of the 1st century A.D.

431 industry are profound. Firstly, it might suggest that there was workshop specialisation in certain

432 forms or groups of forms and that some of these workshops were not acquiring emerald green

433 glass, either because it was deliberately avoided, or as a result of the types of transactions which

434 brought un-worked glass from primary to secondary workshops (an idea suggested by Thirion-

435 Merle (2005) and Foy (2005)). Alternatively, within individual workshops glass workers were

436 perhaps choosing, or avoiding emerald green in the production of certain forms. These ideas are

437 presently being explored in more detail.

439 5. Concluding comments

441 As we have seen, the base glass composition, high in magnesia, potash and carbonaceous

442 material, appears to be advantageous in the formation of a copper-iron emerald green glass. The

443 very fact that emerald green vessels are almost exclusively produced from glass with a plant-ash

444 component, and that vessels of other colours are almost universally natron glasses, re-enforces

445 the theory that this composition did, or was at least perceived to, enhance or facilitate emerald

446 green production.

448 Based on the results of this study, in particular the compositional distinctiveness of the green

449 glass and its use for only certain vessel forms, we can construct more than one possible model

450 for the production and movement of this glass in the context of 1st century A.D. trading

451 networks. For example, certain secondary workshops, with a given repertoire of vessels forms,

452 may have been in a more favourable position to acquire emerald green glass, perhaps on account

453 of their location or their commercial contacts with the primary producers. It is conceivable that

454 emerald green glass was distributed within a set trading framework that changed little over the

455 timespan within which certain forms were produced. A direct link between the vessel makers and

456 the primary producers, by which green was ordered as a specific colour is possible, but might be

457 rather improbable considering the distances involved. However, whether glass was traded freely

458 or subject to some degree of state control is another factor to be taken into account.

460 There may of course be other more local explanations. A workshop receiving raw glass in many

461 colours, and producing a range of different vessel types, may have restricted the use of emerald

462 green to certain forms. Why this might have happened though is unclear. Emerald green does not

463 seem to have been exclusive to vessels requiring the particular levels of workmanship or skill

464 that might imply a higher status. The use of the colour for common and simply produced Isings

465 form 12 cups illustrates this point.

467 One further and important issue that needs to be considered is the timescale within which the

468 production of emerald green glass took place. If we are to judge by the dating associated with the

469 various forms produced in emerald green, then the period of its use ranges from the beginning of

470 the 1st century A.D., for forms such as Isings 2 and Isings 45, to the late 1st or even the early 2nd

471 century for forms such as non-blown plates and bowls with wide out-turned rims (Price and

472 Cottam 1998, 55-9). The height of production seems to occur from around the A.D.20s to the

473 A.D.50/60s. The colour certainly becomes very much less common after the mid 1st century, and

474 at this point production must have been very much reduced, or have ceased entirely, with the

475 continuing appearance of new emerald green vessels reliant on recycling. This much tighter

476 period of production is a possibility, with individual vessels remaining in use over an extended

477 period and broken vessels being preserved for recycling. However if production did stretch

478 across four or more decades, then its use in only a restricted range of vessel forms is all the more

479 curious.

481 What began as an investigation of a single colour has developed into a project with the potential

482 to extend and clarify our understanding of many elements of the 1st century glass industry. The

483 curious link between emerald green, plant-ash glass and the vessel forms that it was used to

484 produce provides an unexpected gateway into the world of the early Imperial glassmaker. We are

485 in the process of extending our dataset to look at emerald green vessel forms of the later 1st

486 century and beyond, the relationship between emerald green and vessels of similar form in other

487 colours, as well as the influence of recycling which will form the basis of further publications, as

488 an extension to our 'green thoughts' .

491 Acknowledgements

492 We would like to thank our colleagues in the Musée Archéologique at Fréjus, Irena Lazar for

493 permission to sample the fragments from Ribnica and Trojane, and the Castle Museum at

494 Colchester for access to the glass fragments for sampling. We thank NERC (NERC

495 OSS/340/0207) for funding trace element analysis at the ICP-MS facility University of

496 Kingston/Imperial College London (Beniot Disch and Kym Jarvis), and EPSRC (through

497 EP/F019750/1 ) for EPMA analysis (Eddy Faber). We would like to thank Sarah Paynter for her

498 generous comments and suggestions on an earlier draft of this paper. The quotation "A green

499 thought in a green shade" comes from Andrew Marvell's poem 'The Garden'.

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673 Legends

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675 (Cottam) are unpublished. References truncated for brevity; Harden 1947, Price and Cottam

676 1996, Cottam and Price 2009, Cool and Price 1995, Cottam unpublished, Lazar unpublished.

678 Table 2. Corning B reference values and data analysis against the standard. Note antimony

679 oxide values are not given for Sheffield as they were corrected for interference (see Lemke 1998,

680 289).

682 Table 3. NIST 612 reference standard for trace elements.

684 Figure 1: Vessel forms discussed in the text.

686 Figure 2: Examples of vessel forms sampled from Ribnica.

688 Figure 3: Concentrations of phosphorus pentoxide and magnesia in Roman emerald green

689 glasses (this study, Adria (Gallo et al. 2013) Fishbourne (Henderson 1996), France (Thirion-

690 Merle 2005) ) compared to Bronze Age Egyptian glasses (Shortland and Eremin 2006),

691 Sassanian glass (Mirti et al. 2008) and Islamic glass from Banias (Freestone 2000).

693 Figure 4: Normalised values of trace and REE elements of a selection of glasses in this study

694 and raw glass from Apollonia (Freestone et al 2000) and sand from Italy (Brems and Degryse

695 2013). Data normalised to continental crust values (Wedepohl 1995).

697 Figure 5. Trace element concentrations of Bronze Age glasses from Egypt (Amarna and

698 Malkata) and Mesopotamia (Nuzi and Tell Brak) showing the different trace element ratios for

699 Cr and La in these two geologically different regions (Shortland et al. 2007), and the early

700 Roman glasses studied here.

702 Figure 6: Lead oxide and antimony oxide concentrations for the different forms of emerald

703 green glasses analysed in this study.

705 Appendix 1: The composition of samples of emerald green Roman glass from Slovenia, France

706 and Britain, analysed using electron probe micro analysis (major and minor elements as wt%

707 oxides). Samples are grouped by site. Catalogue numbers are given from the original

708 publications (see text) and forms (see Table 1). Manufacturing method is given by B, blown;

709 NB, non-blown; MoB, mould blown. nm, not measured; <LLD, below detection.

711 Appendix 2: Trace element compositions for the samples given in Appendix 1, analysed using

712 laser ablation inductively coupled plasma spectrometry. Data expressed as ppm. Key as in

713 Appendix 1.

SITE REPORT AUTHOR CODE CAT NO MANUFACTURE FORM

Barzan Cottam 25635 1 NON BLOWN RETICELLI BOWL (perhaps Isings form 1)

Barzan Cottam 25761 18 M BLOWN CHARIOT CUP

Barzan Cottam 25814 etc 26 M BLOWN CONVEX RIBBED CUP

Barzan Cottam 25111 31 BLOWN ISINGS 12

Barzan Cottam 26310 32 BLOWN ISINGS 12

Barzan Cottam 25144 33 BLOWN ISINGS 12

Barzan Cottam 25533 34 BLOWN ISINGS 12

Barzan Cottam 25533 35 BLOWN ISINGS 12

Barzan Cottam 25816 36 BLOWN ISINGS 12

Barzan Cottam 25234 etc 37 BLOWN ISINGS 12

Barzan Cottam 26473 174 BLOWN JUG

Ribnica Lazar S1296 NON BLOWN BASE RING SMALL CONVEX BOWL, FORM UNCLEAR

Ribnica Lazar S757 NON BLOWN CYLINDRICAL BOWL, ISINGS 22

Ribnica Lazar S1298 NON BLOWN SHALLOW BOWL WITHOUT BASE RING (COMPARABLE WITH ISINGS 5 AND 19)

Ribnica Lazar S1299 NON BLOWN SMALL CYLINDRICAL BOWL, ISINGS 22

Ribnica Lazar S1297 NON BLOWN ISINGS 2

Ribnica Lazar S1270 NON BLOWN BOWL WITH CONVEX SIDE, EXACT FORM UNKNOWN

Ribnica Lazar S1186 BLOWN TUBULAR RIMMED BOWL, ISINGS 45

Ribnica Lazar S1197 NON BLOWN BOWL WITH CONVEX SIDE, COMPARABLE WITH ISINGS 20)

Ribnica Lazar S1161 NON BLOWN SHALLOW BOWL, PROBABLY WITHOUT BASE RING (COMPARABLE WITH ISINGS 5 AND 19)

Ribnica Lazar S1168 ?BLOWN BOWL WITH STRAIGHT SIDE TAPERING IN, EXACT FORM UNKNOWN

Ribnica Lazar S1190 BLOWN TUBULAR RIMMED BOWL, ISINGS 45

Ribnica Lazar S1170 NON BLOWN BASE RING SMALL CONVEX BOWL, FORM UNCLEAR

Ribnica Lazar S1183 BLOWN CUP/BOWL WITH OUT-TURNED RIM, EXACT FORM UNKNOWN

Ribnica Lazar S1171 NON BLOWN BOWL WITH CONVEX SIDE, COMPARABLE WITH ISINGS 20)

Ribnica Lazar S1181 NON BLOWN BOWL/PLATE WITH HORIZONTAL BASE AND LOW BASE RING, FORM UNKNOWN BUT PERHAPS COMPARABLE WITH ISINGS 5

Ribnica Lazar S1210 BLOWN SMALL BOWL WITH CONICAL BODY, COMPARABLE WITH ISINGS 41b)

Ribnica Lazar S1222 NON BLOWN SMALL BOWL WITH SLIGHT CONVEX SIDE, COMPARABLE WITH ISINGS 41a)

Ribnica Lazar S1184 BLOWN BOWL WITH TUBULAR BASE, EXACT FORM UNKNOWN

Ribnica Lazar S1166 BLOWN BOWL WITH VERTICAL RIM, CHANGE OF ANGLE ON UPPER BODY, EXACT FORM UNKNOWN

Trojane Lazar MMK 1216 ?BLOWN BOWL, FORM UNKNOWN

Trojane Lazar MMK 1178 ?BLOWN BOWL, FORM UNKNOWN

Frejus Cottam & Price Argentiere 156 BLOWN ISINGS 12

Frejus Cottam & Price Argentiere 158 BLOWN ISINGS 12

Colchester Cool & Pr ce LWC72 J951 193 NON BLOWN CONVEX BOWL WITH HANDLE

Colchester Cool & Pr ce 1.81 G3627 L3596 198 NON BLOWN PLATE/BOWL, EXACT FORM UNKNOWN

Colchester Cool & Pr ce 1.81 B1764 L389 199 NON BLOWN RECTANGULAR TRAY

Colchester Cool & Pr ce LWC72 J951 200 NON BLOWN SHALLOW BOWL WITH BASE RING (ISINGS FORM 5)

ColchesterLWCool & Pr ce LWC72 J944 203 NON BLOWN BOWL, FORM UNKNOWN

Colchester Cool & Pr ce LWC72 J1464 F184 204 NON BLOWN BOWL, FORM UNKNOWN

Colchester Cool & Pr ce LWC72 J941 208 NON BLOWN UNIDENTIFIED

Colchester Cool & Pr ce LWC72 J1536 F506 279 BLOWN ISINGS 12

Colchester Harden 53a NON BLOWN SHALLOW BOWL (PERHAPS COMPARABLE WITH ISINGS 5)

Colchester Harden 53b NON BLOWN SHALLOW BOWL (PERHAPS COMPARABLE WITH ISINGS 5)

Colchester Harden 56 NON BLOWN CONVEX BOWL (COMPARABLE WITH ISINGS 18)

Colchester Harden 56a NON BLOWN CONXEX BOWL (COMPARABLE WITH ISINGS 18)

Colchester Harden 59 NON BLOWN SMALL CONVEX BOWL (COMPARABLE WITH ISINGS 20)

Colchester Harden 60 NON BLOWN SHALLOW BOWL WITH SLOPING SIDE (PERHAPS COMPARABLE WITH ISINGS 5 AND 19)

Colchester Harden 75a BLOWN ISINGS 12

Colchester Harden 75b BLOWN ISINGS 12

Table 2. Corning B reference values and data analysis against the standard. Note antimony oxide values are not given for Sheffield as they were corrected for interference (see Lemke 1998, 289).

Consensus Brill 1972 Nottingham mean values Sheffield mean values

SiO2 61.5 61.31 62.46

Na2O 17.2 17.50 17.34

CaO 8.69 8.56 8.78

K2O 1.06 1.06 1.03

MgO 1.12 1.10 1.02

Al2O3 4.21 4.49 4.18

FeO 0.33 0.29 0.3

TiO2 0.13 0.07 0.11

Sb2O5 0.45 0.47 **

P2O5 0.9 0.73 0.82

MnO 0.25 0.25 0.25

CuO 2.68 2.79 2.79

V2O5 0.03 0.04 n.d.

SO3 0.55 0.52 0.51

Cl 0.2 0.18 0.17

Table 3. NIST 612 reference standard for trace elements.

NIST612 Analyte Consensus (Pearce et al 1997) Average (n=30)

Sc 41 44.1

Cr 52 Cr 36 37.3

Co 59 Co 35 39.4

Ni 60 Ni 39 43.2

Zn 68 Zn 38 43.4

Ga 71 Ga 36 40.3

Rb 85 Rb 31 36.0

B 11B 35 48.0

Sr 88 Sr 78 74.4

Zr 90 Zr 38 35.6

Ba 137 Ba 40 36.2

La 139 La 36 36.1

Ce 140 Ce 39 ^32.4

Pr 141 Pr 37 35.2

Nd 146 Nd 36 34.8

Sm 147 Sm 38 36.6

Eu 151 Eu 35 35.0

Gd 157 Gd 37 33.5

Tb 159 Tb 36 35.8

Dy 163 Dy 36 33.8

Ho 165 Ho 38 36.4

Er 166 Er 38 33.9

Tm 169 Tm 38 33.8

Yb 172 Yb 39 37.4

Lu 175 Lu 37 35.0

Pb 208 Pb 39 43.2

Th 232 Th 30 35.5

U 238 U 37 40.5

Figure.1

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parities SIUJO^O S8|diuex3 z

idraDSHNVw ааизээу

1.8 1.6 1.4 1.2 1.0

8 08 Q.

0.6 0.4 0.2 0.0

♦ Ribnika

■ Barzan Trojane Camulodunum

X Frejus

• Fishbourne Adria

X France

- Bronze Age Egyptian Sasanian Type 1 Sasanian Type 2

■ Islamic (Banias)

O OoOO

4.0 5.0 MgO (wt%)

—I-1-1

7.0 8.0 9.0

Figure 3: Concentrations of phosphorus pentoxide and magnesia in Roman emerald green glasses (this study, Adria (Gallo et al. 2013) Fishbourne (Henderson 1996), France (Thirion-Merle 2005) ) compared to Bronze Age Egyptian glasses (Shortland and Eremin 2006), Sassanian glass (Mirti et al. 2008) and Islamic glass from Banias (Freestone 2000).

£1 £ ro m

• • •

-Mesopotamian glass

—i-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1

47 52 85 88 90 137141146147151159163172175232238 Ti Cr Rb Sr Zr Ba Pr Nd Sm Eu Tb Dy Yb Lu Th U

Figure 4: Normalised values of trace and REE elements of a selection of glasses in this study and raw glass from Apollonia (Freestone et al 2000) and sand from Italy (Brems and Degryse 2013). The Bronze Age Mycenean/Mesopotamian plant ash glass (Walton et al., 2009) has been included to illustrate the close similarity of the green samples and the glass from Apollonia and provide a distinct contrast.

60.0 50.0 40.0

j| 30.0 u

20.0 10.0

♦ Ribnika ■ Barzan ATrojane

• Camulodunum

+ Frejus +

Nuzi and Tell Brak Amarna and Malkata OAdria

x x * • J?

X y ^_*_

x * X WX X

• ■

0.0 2.0 4.0 6.0 8.0 10.0

La (ppm)

Figure 5. Trace element concentrations of Bronze Age glasses from Egypt (Amarna and Malkata) and Mesopotamia (Nuzi and Tell Brak) showing the different trace element ratios for Cr and La in these two geologically different regions (Shortland et al. 2007), the early Roman emerald green glasses studied here and examples of Roman colourless glass from Adria (Gallo et al., 2013).

Sb2O5 (wt%)

Blown bowls and cups Isings 12 A Other blown forms

□ Mould blown A non-blown bowls/cups O non-blown plates

Figure 6: Lead oxide and antimony oxide concentrations for the different forms of emerald green glasses analysed in this study.

Site Catalogue number Form Manufacturin g method Na2O MgO AI2O3 SiO2 P2O5 SO3 Cl K2O Oxides (wt%) CaO V2O5 MnO FeO TiO2 CuO Ag2O SnO2 Sb2O5

Barzan BRZ1 Isings 1 NB 17.27 1.44 2.65 62.77 0.51 0.25 0.98 1.36 6.47 0.00 0.63 1.02 0.20 2.60 0.00 0.03 0.18

Barzan BRZ174 Jug B 16.96 1.56 2.81 62.32 0.51 0.30 0.92 1.39 6.47 0.01 0.63 1.10 0.21 2.42 0.01 <LLD 0.40

Barzan BRZ18 Chariot cup MoB 16.97 1.78 2.65 61.60 0.61 0.32 0.87 1.53 6.89 0.02 0.73 1.17 0.17 2.10 <LLD <LLD 0.37

Barzan BRZ26 Convex Ribbe MoB 16.87 1.85 2.44 62.51 0.65 0.29 0.94 1.61 6.85 0.04 0.84 1.08 0.15 1.87 0.00 <LLD 0.30

Barzan BRZ31 Isings 12 B 17.06 1.53 2.75 61.95 0.52 0.29 0.95 1.37 6.46 0.01 0.62 1.11 0.19 2.40 0.01 <LLD 0.48

Barzan BRZ32 Isings 12 B 16.48 1.85 2.53 61.70 0.68 0.28 0.88 1.66 6.83 0.01 0.84 1.16 0.16 2.03 0.01 <LLD 0.32

Barzan BRZ33 Isings 12 B 17.24 1.56 2.81 62.03 0.52 0.30 0.87 1.41 6.68 0.03 0.66 1.13 0.19 2.29 0.01 <LLD 0.44

Barzan BRZ34 Isings 12 B 17.06 1.44 2.90 62.53 0.48 0.30 0.91 1.44 6.69 0.01 0.60 1.12 0.20 2.32 0.01 <LLD 0.57

Barzan BRZ35 Isings 12 B 17.47 1.61 2.77 62.52 0.53 0.28 0.99 1.35 6.48 0.01 0.65 1.11 0.23 2.57 0.01 <LLD 0.30

Barzan BRZ36 Isings 12 B 18.55 2.44 1.88 62.21 0.75 0.26 1.31 1.39 6.10 0.02 0.75 1.07 0.14 1.96 0.00 <LLD 0.08

Barzan BRZ37 Isings 12 B 16.60 1.87 2.54 61.92 0.73 0.30 0.89 1.67 6.90 0.02 0.85 1.13 0.16 2.02 0.01 <LLD 0.30

Col (C&P) LWC72 J1536 F506 (279) Isings 12 B 17.04 1.39 2.44 62.66 0.48 0.19 0.82 1.46 6.80 nm 0.64 1.25 0.23 2.53 nm 0.25 0.52

Col (C&P) LWC72 J1464 F184 (204) Bowl NB 15.38 1.99 2.13 62.55 0.96 0.21 0.83 2.19 7.14 nm 1.26 1.49 0.17 1.96 nm 0.19 0.14

Col (C&P) LWC72 J944 (203) Bowl NB 15.37 2.01 2.13 62.68 0.99 0.21 0.82 2.14 7.17 nm 1.34 1.45 0.17 1.93 nm 0.16 0.14

Col (C&P) LWC72 J951 (193) Convex bowl NB 16.09 1.66 2.02 64.50 0.85 0.21 0.88 1.82 6.89 nm 1.02 1.18 0.13 1.77 nm 0.10 0.14

Col (C&P) LWC72 J941 (208) Unid. NB 15.48 1.96 2.07 62.52 0.93 0.21 0.83 2.12 7.07 nm 1.37 1.52 0.17 2.04 nm 0.17 0.10

Col (C&P) 1.81 B1764 L389 (199) Rectangular tiNB 15.20 1.95 2.15 63.66 0.63 0.27 0.85 1.56 7.07 nm 0.90 1.23 0.17 1.23 nm 0.19 0.14

Col (C&P) 1.81 G3627 L3596 (198) Plate/bowl NB 16.92 2.65 1.63 60.88 1.11 0.19 1.11 1.59 6.69 nm 0.59 1.46 0.15 2.28 nm 0.23 0.10

Col (C&P) LWC72 J951 (200) Isings 5 NB 17.48 1.56 2.16 63.04 0.60 0.29 0.88 1.63 6.90 nm 0.89 1.25 0.21 1.80 nm 0.18 0.17

Col(H) 75b Isings 12 B 17.34 1.32 2.47 62.79 0.48 0.27 0.93 1.36 6.55 nm 0.56 1.20 0.27 2.53 nm 0.25 0.57

Col(H) 75a Isings 12 B 17.53 1.34 2.47 63.06 0.51 0.24 0.94 1.38 6.40 nm 0.58 1.23 0.27 2.62 nm 0.25 0.54

Col (H) 56a Isings 18 NB 15.22 2.11 1.68 65.09 0.97 0.21 1.08 1.89 6.94 nm 0.69 1.16 0.15 2.21 nm 0.19 0.14

Col (H) 56 Isings 18 NB 16.72 1.73 2.00 63.94 0.79 0.24 0.93 1.87 6.76 nm 1.03 1.19 0.15 1.87 nm 0.16 0.20

Col (H) 53b Isings 5 NB 16.01 2.01 2.21 63.15 0.81 0.24 0.97 1.77 7.73 nm 0.09 1.39 0.21 2.28 nm 0.19 0.18

Col (H) 53a Isings 5 NB 19.27 1.52 2.37 62.33 0.48 0.37 0.94 1.40 7.07 nm 0.50 1.07 0.21 2.00 nm 0.18 0.12

Col (H) 60 Isings 5/19 NB 15.84 2.66 1.90 63.56 1.18 0.19 0.97 2.03 6.66 nm 0.55 1.42 0.19 2.33 nm 0.19 0.20

Col (H) 59 Isings 20 NB 17.79 1.61 2.47 62.47 0.51 0.35 0.90 1.47 7.44 nm 0.62 1.31 0.23 2.11 nm 0.21 0.17

Frejus 156 Isings 12 B 17.38 0.97 2.27 65.92 0.39 0.16 0.81 1.13 6.96 nm 0.64 0.85 0.17 2.63 nm 0.26 0.33

Frejus 158 Isings 12 B 17.57 0.83 2.43 65.39 0.27 0.16 0.86 1.01 7.15 nm 0.59 0.73 0.13 2.11 nm 0.19 0.34

Trojane MMK1178 Bowl ?B 16.11 2.65 2.34 61.76 0.97 0.26 0.84 1.95 7.51 0.02 0.92 1.24 0.17 2.21 0.01 <LLD 0.19

Trojane MMK1216 Bowl ?B 16.52 2.43 2.19 61.77 0.90 0.27 0.94 1.78 7.03 nm 0.88 1.14 0.14 2.05 0.01 <LLD 0.20

Ribnica S1161 Isings 5/19 NB 15.47 2.23 2.44 62.25 0.88 0.29 0.80 2.26 7.11 0.01 1.06 1.29 0.15 2.08 0.01 <LLD 0.19

Ribnica S1166 Bowl B 15.74 2.75 1.90 62.00 1.11 0.23 0.86 2.28 7.44 0.02 0.93 1.15 0.12 2.43 0.01 <LLD 0.19

Ribnica S1168 Bowl ?B 15.18 3.47 2.17 62.44 1.09 0.16 0.96 1.94 6.83 0.01 0.53 1.23 0.15 2.32 0.00 <LLD 0.13

Ribnica S1170 Bowl NB 16.34 1.54 2.42 63.58 0.48 0.18 1.15 1.49 5.66 0.01 0.90 1.51 0.38 3.16 0.01 0.04 0.08

Ribnica S1171 Isings 20 NB 17.10 1.90 2.48 62.45 0.60 0.32 0.85 1.61 6.79 0.02 0.92 1.07 0.16 2.14 0.01 <LLD 0.14

Ribnica S1181 Isings 5 NB 16.75 1.85 2.10 63.56 0.75 0.23 1.08 1.91 5.63 0.03 0.79 1.00 0.13 2.32 0.00 <LLD 0.14

Ribnica S1183 Cup/Bowl B 15.15 3.44 2.17 62.23 1.10 0.18 0.97 1.96 6.81 0.02 0.54 1.24 0.16 2.34 0.01 <LLD 0.13

Ribnica S1184 bowl B 17.10 2.14 2.22 63.25 0.76 0.26 0.96 1.56 6.99 0.01 0.85 1.12 0.12 1.69 0.00 <LLD 0.29

Ribnica S1186 Isings 45 B 17.30 2.31 1.87 62.11 0.75 0.27 1.00 1.62 5.98 0.03 1.41 0.99 0.13 2.22 0.01 <LLD 0.22

Ribnica S1190 Isings 45 B 15.97 2.75 2.21 61.15 0.96 0.28 0.87 1.96 7.68 0.02 0.92 1.26 0.16 2.42 0.01 <LLD 0.20

Ribnica S1197 Isings 2 NB 17.30 1.96 2.48 62.59 0.60 0.34 0.86 1.61 6.83 nd 0.92 1.06 0.14 2.09 0.00 <LLD 0.14

Ribnica S1210 Isings 41b B 16.81 2.20 2.16 61.57 0.83 0.28 0.96 1.74 7.02 0.03 0.86 1.09 0.13 2.13 0.01 <LLD 0.24

Ribnica S1222 Isings 41a NB 16.39 2.18 2.33 61.05 0.82 0.31 0.89 2.10 7.47 0.01 0.96 1.14 0.15 2.16 <LLD <LLD 0.15

Ribnica S1270 Bowl NB 16.09 2.07 2.27 63.98 0.81 0.26 0.90 1.91 6.52 0.05 0.97 1.19 0.14 1.87 0.01 <LLD 0.14

Ribnica S1296 Convex bowl NB 19.87 1.06 3.74 63.99 0.08 0.31 1.27 0.56 3.69 0.02 0.24 1.32 0.38 2.85 0.00 0.17 0.02

Ribnica S1297 Isings 2 NB 16.12 2.21 2.29 62.43 0.81 0.33 0.89 1.75 6.70 0.01 1.05 1.36 0.13 1.80 0.00 <LLD 0.14

Ribnica S1298 Isings 5/19 NB 15.30 2.30 2.40 63.13 0.81 0.31 0.80 2.25 6.92 0.02 0.99 1.35 0.16 1.96 <LLD <LLD 0.16

Ribnica S1299 Isings 22 NB 20.00 2.37 3.44 60.09 0.42 0.44 0.87 1.18 6.10 0.02 0.55 1.40 0.36 2.90 0.00 0.00

Ribnica S757 Isings 22 NB 16.17 0.99 2.95 67.23 0.15 0.19 1.03 0.72 4.83 0.02 0.97 1.19 0.20 2.03 0.00 0.05

Trace elements (ppm)

Catalogue Number 11 B 45 Sc 52 Cr 59 Co 60 Ni 68 Zn 71 Ga 85 Rb 88 Sr 90 Zr 137 Ba 139 La 140 Ce 141 Pr 146 Nd 147 Sm 151 Eu 157 Gd 159 Tb 163 Dy 165 Ho 166 Er 169 Tm 172 Yb 175 Lu 208 Pb 232 Th 238 U

BRZ1 139.2 5.0 23.5 18.1 11.7 73.2 2.5 12.1 407.7 126.4 316.8 7.17 12.39 1.56 6.78 1.59 0.48 1.11 0.14 1.30 0.27 0.67 0.11 0.76 0.09 2219.3 1.8 1.1

BRZ174 160.0 5.1 26.0 26.7 12.4 69.9 2.8 12.7 409.8 115.2 335.2 7.53 12.25 1.73 7.93 1.24 0.41 1.34 0.22 1.36 0.28 0.80 0.13 0.61 0.12 3505.2 1.9 1.1

BRZ18 185.9 4.7 20.8 32.4 13.7 73.0 2.8 15.3 471.0 87.5 356.5 7.97 11.75 1.72 7.27 1.91 0.35 1.04 0.18 1.16 0.22 0.62 0.11 0.60 0.08 3578.4 1.6 1.3

BRZ26 177.9 5.1 17.1 45.4 14.2 82.5 2.5 9.5 462.7 74.8 309.5 6.57 10.25 1.51 6.46 1.36 0.36 1.17 0.19 0.81 0.26 0.57 0.11 0.60 <LLD 1813.9 1.3 1.0

BRZ31 154.7 4.9 24.6 34.9 11.4 61.1 2.9 13.6 416.6 106.0 337.2 8.16 12.75 1.64 8.07 1.25 0.31 1.27 0.17 0.99 0.24 0.53 0.13 0.81 0.12 4376.5 1.9 1.1

BRZ32 167.0 4.8 16.3 30.5 12.4 68.8 2.6 12.5 447.0 80.4 327.2 7.46 10.98 1.59 6.75 1.77 0.33 1.01 0.14 0.59 0.25 0.45 0.11 0.59 0.10 2915.2 1.7 1.1

BRZ33 169.1 5.4 23.3 27.4 11.8 66.8 2.8 15.5 421.6 100.5 340.0 7.61 11.91 1.72 7.33 1.41 0.39 1.01 0.22 1.36 0.27 0.59 0.12 0.61 0.24 4852.3 1.7 1.2

BRZ34 140.4 4.9 25.9 41.6 11.6 62.8 2.9 27.8 405.6 114.6 337.6 8.95 13.32 1.89 7.72 1.28 0.37 1.34 0.20 1.44 0.25 0.74 0.12 0.80 0.08 3931.0 2.2 1.0

BRZ35 159.1 5.1 26.7 17.0 11.2 61.2 2.8 11.1 398.1 123.7 321.9 7.31 11.39 1.73 7.08 1.48 0.46 1.18 0.15 1.08 0.25 0.94 0.16 0.57 0.11 2980.9 1.7 1.2

BRZ36 185.4 4.5 12.4 19.0 13.8 120.2 2.2 5.4 425.4 79.8 208.5 6.19 9.02 1.21 5.38 1.02 0.33 1.06 0.22 0.90 0.16 0.43 0.08 0.62 0.08 311.2 1.2 0.9

BRZ37 173.3 4.9 17.9 33.6 13.1 86.5 2.6 14.4 459.1 79.5 315.3 7.10 10.81 1.58 6.28 1.19 0.36 1.21 0.18 1.01 0.23 0.79 0.10 0.65 0.09 3113.3 1.5 0.9

Col LWC 72 J1536 F506 (279) nm nm 22.3 22.9 9.8 67.5 2.7 11.4 404.9 110.1 294.7 7.37 12.34 1.45 6.37 1.02 0.29 0.94 0.24 0.89 0.22 0.65 0.12 0.54 0.10 3192.4 1.7 0.9

Col LWC 72 J1464 204 nm nm 12.7 16.9 14.4 78.3 2.4 9.0 524.4 63.5 390.6 5.96 10.13 1.26 5.24 0.86 0.21 0.99 0.10 0.75 0.19 0.44 0.06 0.41 0.05 423.5 0.9 0.7

Col LWC 72 J944 (203) nm nm 13.7 17.5 14.9 70.4 2.1 8.9 521.3 64.2 397.0 5.76 9.71 1.20 5.30 0.97 0.26 0.74 0.17 0.73 0.18 0.47 0.07 0.57 0.08 409.4 1.0 0.7

Col LWC 72 J951 (193) nm nm 15.0 11.2 14.5 65.3 2.3 9.0 478.9 55.8 271.8 5.26 10.10 1.14 5.16 1.14 0.28 0.79 0.14 0.65 0.20 0.42 0.05 0.42 0.07 431.7 0.9 0.9

Col LWC 72 J941 208 nm nm 14.4 17.2 14.6 64.4 2.9 7.8 491.8 67.9 362.0 5.42 9.90 1.18 5.06 1.42 0.32 1.08 0.18 0.79 0.20 0.38 0.08 0.42 0.12 392.1 1.0 0.7

Col 1.81 B176 L389 (199) nm nm 138.8 12.3 17.0 69.1 2.6 7.6 468.9 74.5 320.4 5.91 10.98 1.36 5.32 1.59 0.25 0.91 0.14 0.75 0.37 0.60 0.14 0.43 0.08 668.0 1.0 0.7

Col 1.81 G3627 L3596 (198) nm nm 10.4 14.0 9.1 184.6 1.8 4.0 439.7 71.5 272.8 4.78 7.81 0.99 4.39 0.67 0.17 0.79 0.08 0.70 0.12 0.36 0.07 0.30 0.07 319.7 1.1 0.5

Col LWC72 J951 (200) nm nm 19.3 9.7 11.4 66.5 2.3 7.4 455.5 73.1 365.2 5.83 10.89 1.37 5.54 1.25 0.30 0.88 0.15 0.72 0.15 0.44 0.09 0.50 0.07 928.9 1.1 0.9

Col 75b nm nm 22.6 26.9 8.6 60.4 2.6 13.2 388.8 118.2 287.9 7.62 12.73 1.53 6.43 1.72 0.26 1.17 0.15 1.08 0.23 0.73 0.09 0.67 0.09 3069.5 1.7 0.9

Col 75a nm nm 25.9 18.8 10.9 57.3 3.3 11.5 392.3 133.6 287.7 6.68 11.41 1.50 7.49 1.32 0.47 1.30 0.18 0.99 0.18 0.72 0.08 0.40 0.12 2389.8 1.8 0.8

Col 56a nm nm 11.3 42.6 17.6 73.6 1.8 5.9 442.0 69.0 242.0 4.79 8.24 0.98 4.86 0.84 0.27 1.02 0.10 0.57 0.14 0.47 0.11 0.35 0.03 227.6 0.9 1.0

Col 56 nm nm 11.5 9.5 11.7 40.0 2.0 7.1 460.0 58.1 265.4 5.36 9.31 1.18 5.62 0.86 0.22 0.66 0.10 0.88 0.15 0.45 0.06 0.57 0.06 327.0 0.9 0.7

Col 53b nm nm 16.9 8.1 9.0 41.6 2.4 6.3 548.6 87.2 467.3 6.40 10.97 1.33 5.60 1.31 0.34 1.07 0.16 0.97 0.21 0.43 0.09 0.61 0.07 631.4 1.2 0.8

Col 53a nm nm 18.2 5.6 9.4 32.7 2.6 6.0 434.1 72.7 331.5 6.75 12.00 1.37 6.13 0.92 0.32 0.94 0.14 1.02 0.19 0.48 0.08 0.46 0.07 526.2 1.0 1.1

Col 60 nm nm 13.5 19.4 11.5 168.9 2.2 4.0 437.0 99.2 235.5 5.50 8.96 0.99 4.41 0.98 0.23 0.80 0.20 0.69 0.14 0.51 0.05 0.59 0.05 319.6 1.4 0.7

Col 59 nm nm 19.9 6.6 10.5 59.7 3.3 5.6 463.5 101.9 325.6 6.81 10.71 1.43 6.40 1.69 0.16 1.30 0.16 1.05 0.23 0.38 0.07 0.34 0.09 584.4 1.5 1.0

Frejus 156 nm nm 17.9 35.6 13.3 83.5 2.4 8.7 417.3 89.7 212.1 7.03 11.31 1.30 7.36 1.18 0.29 0.81 0.21 1.19 0.21 0.56 0.08 0.64 0.11 2743.0 1.3 0.9

Frejus 158 nm nm 16.7 40.8 11.3 49.4 2.1 10.2 388.6 71.6 226.8 7.62 12.49 1.63 7.80 1.86 0.43 1.27 0.24 1.32 0.22 0.81 0.15 1.12 0.10 3224.0 1.7 1.2

MMK1178 184.7 4.7 17.5 29.4 15.8 139.1 2.4 7.4 539.7 82.1 282.5 7.02 9.82 1.43 5.65 1.50 0.37 1.12 0.16 0.86 0.20 0.57 0.06 0.66 0.11 1305.5 1.3 0.9

MMK1216 181.6 4.9 14.3 31.1 13.4 110.3 2.0 7.0 485.2 79.8 258.6 6.30 9.61 1.23 5.53 1.39 0.25 0.99 0.16 0.98 0.23 0.58 0.10 0.43 <LLD 816.4 1.3 0.7

S1161 268.6 7.6 15.1 11.7 15.7 80.8 2.5 13.0 503.5 67.2 366.1 6.40 9.72 1.30 5.87 1.28 0.36 0.91 0.15 0.77 0.22 0.51 0.09 0.59 0.09 607.8 1.2 1.0

S1166 158.6 4.6 12.8 21.8 14.5 143.8 1.9 7.8 529.8 66.1 257.2 6.02 8.95 1.15 5.23 0.77 0.28 0.84 0.12 0.68 0.20 0.42 0.07 0.54 0.09 416.4 1.1 0.7

S1168 199.9 6.7 13.5 18.3 13.9 175.9 2.3 4.5 485.9 86.9 233.7 6.46 9.80 1.36 6.41 1.05 0.24 0.99 0.12 0.81 0.18 0.43 0.08 0.46 0.08 276.0 1.3 1.1

S1170 335.4 8.5 33.9 5.3 11.8 43.7 2.7 8.5 410.8 255.4 478.3 8.51 12.96 1.93 8.27 0.83 0.40 1.28 0.22 1.39 0.34 0.94 0.15 1.09 0.16 37.9 2.3 1.2

S1171 310.4 7.3 16.0 11.6 14.6 81.9 2.7 9.6 456.2 75.6 382.6 6.47 9.68 1.47 6.49 0.86 0.33 0.75 0.19 1.20 0.24 0.45 0.06 0.56 0.11 748.5 1.3 1.0

S1181 178.8 7.4 11.8 10.5 13.4 86.9 1.9 10.2 394.8 78.8 238.3 6.17 9.15 1.25 4.93 1.18 0.33 0.75 0.14 0.88 0.22 0.53 0.14 0.72 <LLD 461.7 1.4 0.7

S1183 284.6 8.5 13.1 20.2 16.1 171.3 2.1 5.0 460.1 83.4 217.7 6.05 9.51 1.31 5.47 1.37 0.44 1.07 0.17 0.80 0.15 0.56 0.11 0.65 0.13 295.9 1.3 0.9

S1184 164.1 5.1 13.8 127.1 14.8 105.0 2.4 7.3 471.4 71.5 273.9 6.61 9.69 1.36 5.54 0.86 0.27 1.14 0.14 1.11 0.18 0.51 0.09 0.65 0.14 1355.2 1.2 1.0

S1186 164.4 6.1 10.3 19.4 18.7 162.0 1.9 5.5 478.8 72.3 252.9 5.32 7.87 1.12 5.29 0.68 0.26 0.71 0.17 0.77 0.16 0.37 0.09 0.51 0.09 471.5 1.1 0.8

S1190 279.7 7.2 15.5 28.5 16.2 157.0 2.4 8.6 559.2 79.7 264.7 6.16 9.90 1.40 5.68 1.08 0.28 1.22 0.17 0.95 0.18 0.52 0.09 0.69 <LLD 1260.3 1.4 0.9

S1197 273.0 6.9 17.2 12.9 13.1 99.9 2.8 9.9 464.6 74.7 388.7 6.87 10.26 1.57 6.01 1.20 0.27 0.85 0.19 1.25 0.20 0.79 0.08 0.56 0.08 834.3 1.2 1.2

S1210 184.5 7.7 13.6 31.0 16.0 120.0 2.3 7.8 482.6 72.3 255.5 5.57 9.35 1.41 5.45 1.04 0.43 1.12 0.21 0.95 0.19 0.43 0.08 0.61 <LLD 1124.4 1.2 0.8

S1222 208.4 5.7 16.8 10.1 12.8 73.4 2.3 10.3 516.4 77.0 414.1 6.47 10.31 1.47 6.29 1.51 0.36 0.99 0.16 1.23 0.17 0.74 0.09 0.70 0.13 1194.6 1.2 1.1

S1270 133.9 7.2 12.8 14.7 12.7 52.4 2.4 9.0 458.5 58.9 290.6 5.86 9.07 1.40 5.90 1.29 0.30 1.09 0.20 0.92 0.21 0.60 0.10 0.62 <LLD 393.7 1.0 0.9

S1296 455.1 13.9 42.6 5.2 12.9 80.4 3.4 5.9 235.5 122.8 240.3 8.41 12.54 1.79 8.34 1.62 0.39 1.20 0.20 1.36 0.33 0.82 0.12 0.98 0.14 224.9 1.9 1.1

S1297 161.5 11.3 12.8 29.1 17.6 98.1 2.2 8.9 485.5 58.7 286.6 6.21 9.14 1.24 4.72 1.14 0.29 0.84 0.18 0.95 0.24 0.53 0.11 0.73 0.16 645.4 1.0 0.9

S1298 163.8 11.5 14.3 10.6 15.7 82.5 2.5 13.1 492.1 65.8 357.4 6.14 9.90 1.52 5.65 1.35 0.32 1.05 0.17 1.26 0.22 0.65 0.09 0.67 <LLD 532.4 1.2 0.8

S1299 265.7 12.5 31.6 5.9 11.4 41.7 3.1 7.3 368.6 168.3 376.9 8.80 13.45 1.93 8.63 1.66 0.41 1.52 0.20 1.21 0.25 0.78 0.10 0.69 0.12 385.2 2.2 1.3

S757 218.8 13.9 15.7 6.9 16.2 54.1 2.8 6.3 321.5 89.3 376.4 7.49 10.91 1.55 7.11 1.11 0.36 1.16 0.24 1.34 0.23 0.59 0.13 0.60 0.12 179.1 1.7 1.0