Catalogue of 45 Reference Raman Spectra of Minerals Concerning Research in Art History Or Archaeology, Especially on Corroded Metals and Coloured Glass
Total Page：16
File Type：pdf, Size：1020Kb
Spectrochimica Acta Part A 59 (2003) 2247Á/2266 www.elsevier.com/locate/saa Catalogue of 45 reference Raman spectra of minerals concerning research in art history or archaeology, especially on corroded metals and coloured glass M. Bouchard *, D.C. Smith Baˆtiment Mine´ralogie, Muse´um National d’Histoire Naturelle and CNRS, 61 Rue Buffon, 75005 Paris, France Received 23 June 2002; accepted 15 August 2002 Abstract Small catalogues of reference Raman spectra of interest for analysing geomaterials or biomaterials of relevance to art history or archaeology are gradually being published by different research groups. However, except for some older catalogues, they are all concerned primarily with pigments, whether inorganic or organic. Here we present for the first time a catalogue of Raman spectra of minerals that may be found in corroded metal artworks or artefacts. At the same time we include some inorganic pigments that may be found in or on stained glass. Most of the minerals analysed came from the Gallery of Mineralogy at the Muse´um National d’Histoire Naturelle and most were verified by X-ray diffraction in order to augment the confidence in the mineral identity (which is not the case with many other catalogues). A number of problems encountered with mineral terminology are discussed. Comments are made on the spectra where appropriate. # 2003 Elsevier B.V. All rights reserved. Keywords: Raman spectroscopy; Catalogue; Reference spectra; Art; Archaeology 1. Introduction and tissues), the whole having been defined as ‘ARCHAEORAMAN’ [1,2], is the lack of ade- A major problem for a relatively ‘young’ quate databases of ‘reference Raman spectra’, i.e. discipline such as non-destructive Raman Micro- spectra obtained from known inorganic, organic scopy (RM) applied to Archaeology and Art or amorphous species. The basis of species identi- History in general, i.e. not only to pigments but fication by RM is the comparison of the spectrum also to geomaterials (e.g. rocks, gems, ceramics, of an unknown material with reference spectra glass and metals) and to biomaterials (e.g. resins (‘Raman spectral fingerprinting’). A poorly-docu- mented database will thus handicap any identifica- tion. Very few databases existed until recently: by * Corresponding author. Tel.: /33-1-4079-3527; fax: /33-1- Griffith on crystals [3], Guineau on pigments [4], 4079-3524. E-mail address: [email protected] (M. and Pinet et al. on gemstones [5]. Since then the Bouchard). database on pigments by Bell et al. [6] has been 1386-1425/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S1386-1425(03)00069-6 2248 M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 updated by Burgio and Clark [7] and a consider- cm1, the samples were simply placed in turn in able number of new research teams are building up the exciting laser beam under the microscope their own databases on pigments. objective. The Raman spectra were mostly mea- We decided in 1997 to prepare a new database sured with the following operational conditions: concerning products likely to be observed in two red He/Ne laser excitation at 632.8 nm; 30 mW new domains of RM archaeometrical research: laser power at source reduced considerably by corrosion products of metals (e.g. sculptures, various filters and by the optical trajectory; /10, weapons or tools), and pigments and alterations /50 or /100 objective; 300 mm slits; multi- of stained glass (e.g. windows). The prestigious channel CCD detection; integration time 50Á/400 mineral collection of the Gallery of Mineralogy of s and two to seven accumulations. Green Ar the MNHN provides an excellent selection of laser radiation at 514.5 nm was also sometimes thousands of natural mineral species. Most of the used with variable but low laser power to reduce spectra presented in this catalogue came from heating of the sample. For routine analysis, 9/3 samples of this collection and most of these cm1 is considered to be the accuracy when minerals were checked by X-ray powder diffrac- comparing spectra from different samples, on tion (XRD) to verify that their Museum labelling different days, or from different instruments; the 1 was correct [8]. Most of the modern pigments here precision of RM being around 9/1cm . The were kindly provided by the ‘Atelier Debitus’ spectra published here were sometimes established stained-glass factory at Tours, France, but several by the simple addition of one spectrum obtained had previously been purchased by them from with the laser beam polarisation vertical and one commercial pigment manufacturers. with the laser beam polarisation horizontal, with- The Raman spectral data are presented below in out moving the sample at all, in order to take an identical format. Each paragraph starts with account of the crystal axis orientation effect and of the F codenumber that gives the ‘fiche’ (file or the optical trajectory orientation effect [9]. The index card) number of the corresponding XRD spectra presented were sometimes treated by base- data (the sign £ for confirmed spectra and no sign line correction and/or minor smoothing. for non-confirmed spectra). The XRD data are available from the authors. This is followed by the mineral group name, mineral species name, ideal chemical composition, crystal system and space 3. Terminological and other problems group. The second line lists the observed Raman wavenumbers, with underlining indicating the In all cases where it was possible to extract a relatively stronger bands and an asterisk the minute portion of crystal from the Gallery, an weaker ones (or shoulders). All the plotted spectra XRD identification was carried out to confirm the appear in Fig. 1 and can be identified by their F nature of the mineral species by reference to codenumber as well as their mineral species name. international powder diffraction tables. A consid- The order of the mineral species is based on erable number of problems were encountered and mineral groups as shown in Table 1 where an our procedure for dealing with them is outlined alphabetical list is also supplied. For simplicity the below. Over 70 species were collected from the adjectival term ‘hydroxy-’ here includes minerals Gallery or the ‘Atelier’ but only 45 finally arrived with (OH) and/or H2O. in this catalogue. 1) Minerals in the Gallery, being natural miner- 2. Experimental als, are very often mineral mixtures and whereas it was usually obvious to an experi- The Raman Microscope employed was a enced mineralogist which was which, this DILOR† XY† instrument. After wavenumber was not always the case and it was then calibration using the diamond peak at 13329/1 necessary to analyse each of the mineral M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 2249 Fig. 1. The Raman spectrum obtained from each of the 45 minerals described in this catalogue, each one being labelled by the species name preceded by our computer code F number as used in the text. Abscissa: wavenumber in cm1. Ordinate: arbitrary units. 2250 M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 Fig. 1 (Continued) M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 2251 Fig. 1 (Continued) 2252 M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 Fig. 1 (Continued) M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 2253 Fig. 1 (Continued) 2254 M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 Fig. 1 (Continued) M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 2255 Fig. 1 (Continued) 2256 M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 Fig. 1 (Continued) M. Bouchard, D.C. Smith / Spectrochimica Acta Part A 59 (2003) 2247Á/2266 2257 Table 1 species present (e.g. a sample labelled ‘man- Mineral species names and F codenumbers arranged by mineral ganite and polianite’). group and also alphabetically 2) The polymineralic situation also occurred Lexicon arranged by Alphabetical lexicon when only one species was listed as being mineral group present (e.g. in a sample labelled ‘anglesite’ Oxides Anglesite F17 the results revealed a rather large quantity of F1*/Cuprite Antlerite F13 cerussite coupled with only a small amount F2 */Hematite Atacamite F25 of anglesite; likewise ‘langite’ was in fact F3 */Litharge et massicot Aurichalcite F38 F4 */Minium Azurite F35 brochantite with a little langite). F5 */Zinc oxide Boleite F30 3) No exploitable Raman spectra were obtained F6 */Zincite Botallackite F27 F7 */Cassiterite Brochantite F15 due to the great opacity of certain minerals, F8 */‘Cobalt oxide’ Buttgenbachite F43 and sometimes due to the Raman selection F9 */Eskolaite Calumetite F28 rules (e.g. no data from the samples labelled: Oxy-Hydroxides Cassiterite F7 F10 */Goethite Cerussite F3 ‘chalcocite’, ‘eurubexite/chalcopyrite’ (in F11 */Lepidocrocite Chalcanthite F14 fact bornite by XRD analysis), ‘acanthite’, F12 */Manganite Chlorargyrite F23 (Cerargirite) ‘galena’, ‘chlorargyrite’, ‘melanothallite’, Sulphates and hydroxy- Clinoatacamite F26 ‘percylite’, and ‘chrysocolla’). sulphates 4) When the XRD spectrum did not correspond F13 */Antlerite Cobalt oxide F8 F14 */Chalcanthite Connellite F42 to the species name on the sample label, then F15 */Brochantite Cotunnite F23 two possible situations arose: F16 */Linarite Covellite F18 F17 */Anglesite Cumengite F29 i) If the new XRD identification pre- Sulphides Cuprite F1 sented some interest, then the sample