Scorpions diverged from their closest relatives around the Ordovician Period, and since then, environmental interactions have shaped the evolution of the material properties of their exoskeletons. Hardening of this structure via the incorporation of transition metals has enabled biomechanical advancements in weapon development. Scorpion weapons consist of the stinger (telson) and claws (chelae) and contain diverse metals such as zinc, manganese and iron, though little is known about comparative patterns of incorporation across the wider clade. In this study, we harness X-ray-driven microanalytical techniques to characterize the different elemental enrichment patterns within the weapons of 18 species from a range of scorpion families. We hypothesized that enrichment by metal would be inversely correlated between weapons, tied to their functional roles and morphological diversity. We identified cryptic enrichment strategies, including weapon-selective elemental replacement and an inverse enrichment of Zn between weapons. Chela enrichment by Zn was found to positively correlate with a morphological indicator of chelae pinch strength, wherein Zn enrichment was greater in specimens with reduced crushing power. This study supports a growing body of research into the evolution of metal enrichment among invertebrates and provides a greater understanding of the material properties of the exoskeleton within weapon development.

The shells of muricoid gastropod Ecphora gardnerae from the Miocene St. Marys Formation of Maryland, USA, have been shown to contain polymeric sheets within the calcareous matrix. These membranes were found to have amino acids and complex sugar compounds. To explore these biomolecular features further, four new E. gardnerae shells were collected and analyzed for proteins and sugar compounds. Using direct analysis in real time (DART) mass spectrometry, we were able to show that the membranes contain chitin. With mass spectrometry-based paleoproteomic techniques utilizing a hydroxylamine extraction or sample preparation by easy extraction and digestion (SPEED), we found preserved peptides from all four shells including peptides that are specific to Gastropoda or Mollusca. The membranes derive from the calcitic layer of the shell and are likely analogous to chitin membranes used by other extant mollusks to control nucleation, growth, and physical properties in the calcareous layers, but future research in gastropod biology will help to address the function of these membranes.

Egyptian blue (EB) is a heterogeneous multi-phase blue pigment originating in Egypt approximate to 5000 years ago. While cuprorivaite (CaCuSi4O10) is the primary chromophore, color of the powdered pigment depends upon multiple factors, including other phases and particle size. In this study, we synthesized EB using differing raw materials and heating times and investigated the phases and microstructure of the particles via X-ray diffraction, electron beam X-ray microanalysis, and X-ray nano-computed tomography. We measured color by reflectance visible/near-infrared spectrometry and color coordinate extraction and obtained comparative measurements on modern pigments, two Egyptian artifacts (approximate to 2300-3400 years old), and synthesized Cu-doped glasses. Photoluminescence mapping of the artifacts confirmed intergrowth of cuprorivaite encased within colorless particles which otherwise appear as a single phase. This accurate determination of color coupled with correlation to phase distribution provides a series of recipes for obtaining given colors, knowledge which is useful for archeologists and conservation scientists working with EB materials.

Animal-based metal threads were largely used between the 10th and the fifteenth century, in European, Middle Eastern and Far Eastern textile productions for the decoration of textiles and cloths. They belong to a larger group of metal threads, used either as flat threads or wrapped around a fiber core, that were backed by an organic support (animal or paper). This study focuses on the medieval production of metal threads backed by an animal membrane (e.g. gut membrane), or skin. A total of 91 samples were collected from a corpus of 66 textile fragments belonging to 54 catalogued objects. The relevance and novelty of the present study is represented by the combination of proteomics, cross-section analysis, and scanning electron microscopy (SEM–EDS and SEM-µXRF). The diversity of materials and manufacturing techniques found within each typology of thread, respectively, membrane-based metal threads and skin-based metal threads, hinted at different production technologies. Membrane-based threads were found to be invariably made from cattle gut membrane, coated with gilt-silver leaves. A possible sheep glue adhesive was found in a few samples. Skin-based threads were made from either goat or sheep leather, coated with metal leaves or powder. Within the three different types of coatings identified (silver, gold and gilt-silver), gold coatings were the most represented. Goat leather threads were associated with an egg-white binder, while sturgeon glue was identified as adhesive in all sheep leather threads. Collagen glue from other species (cattle, sheep, horse) was occasionally found in mixed adhesives. In two textiles, the finding of human proteins indicates past contamination due to handling or use. The analytical results show coherence between the fabrication patterns of animal-based metal threads and their probable geographical areas of manufacture, indicating that the study of materials and techniques provide further criteria to classify and group textiles, and trace correlations between manufacturing centers within Eurasian territories.

Many textiles produced by Native American Woodlands cultures are made from bast (phloem) fibers from North American plants. While bast fibers are easy to identify with microscopy, determining the exact species has long been a challenge. Historically, bast fibers from Native American communities have been referred to as "Indian hemp," a confusing term at best. This project undertaken as part of an Andrew W. Mellon Fellowship at the National Museum of the American Indian (NMAI) focused on a combined approach by working with both community members and scientists to provide a cultural background for these important fibers as well as useful diagnostic tools for identification. Both macroscopic and microscopic characteristics were examined including color, feel, microfibrillar orientation, crystal species, and cross section analysis. A physical and digital reference collection was created for comparison. Eight fiber samples taken from six historic objects in NMAI's collection were then examined to test effectiveness of bast fiber identification protocol. Results from this study confirm there continues to be limited success when identifying the exact bast fiber species in historic artifacts because of small sample size and aging characteristics. De nombreux textiles produits par les cultures am & eacute;rindiennes des for & ecirc;ts sont fabriqu & eacute;s & agrave; partir de fibres lib & eacute;riennes (phlo & egrave;me) de plantes d'Am & eacute;rique du Nord. Bien que les fibres lib & eacute;riennes soient faciles & agrave; identifier au microscope, la caract & eacute;risation de l'esp & egrave;ce exacte a longtemps pos & eacute; des difficult & eacute;s. Historiquement, les fibres lib & eacute;riennes des communaut & eacute;s am & eacute;rindiennes ont & eacute;t & eacute; appel & eacute;es "chanvre indien", un terme pour le moins confus. Ce projet, entrepris dans le cadre d'un Andrew W. Mellon Fellowship au National Museum of the American Indian (NMAI), s'est concentr & eacute; sur une approche collaborative entre des membres de la communaut & eacute; am & eacute;rindienne et des scientifiques, afin d'apporter un contexte culturel & agrave; ces fibres importantes, ainsi que des outils de diagnostic utiles pour leur identification. Les caract & eacute;ristiques macroscopiques et microscopiques ont & eacute;t & eacute; examin & eacute;es, notamment la couleur, le toucher, l'orientation microfibrillaire, les esp & egrave;ces de cristaux et l'analyse des coupes stratigraphiques. Une collection de r & eacute;f & eacute;rence, physique et num & eacute;rique, a & eacute;t & eacute; cr & eacute;& eacute;e & agrave; des fins de comparaison. Huit & eacute;chantillons de fibres pr & eacute;lev & eacute;s sur six objets historiques de la collection du NMAI ont ensuite & eacute;t & eacute; examin & eacute;s afin de tester l'efficacit & eacute; du protocole d'identification des fibres lib & eacute;riennes. Traduit par Stephanie Auffret. Muitos t & ecirc;xteis produzidos pelas culturas das florestas nativas americanas s & atilde;o feitos de fibras bast/liberianas (floema) de plantas norte-americanas. Enquanto as fibras liberianas s & atilde;o f & aacute;ceis de identificar com microscopia, determinar as esp & eacute;cies exatas tem sido um desafio h & aacute; muito tempo. Historicamente, as fibras liberianas de comunidades nativas americanas t & ecirc;m sido chamadas como "c & acirc;nhamo indiano", um termo confuso, na melhor das hip & oacute;teses. Este projeto realizado como parte de uma bolsa da Andrew W. Mellon no National Museum of the American Indian (NMAI) teve como foco uma abordagem combinada, trabalhando com membros da comunidade e com cientistas, para fornecer uma base cultural para estas importantes fibras assim como ferramentas de diagn & oacute;stico & uacute;teis para identifica & ccedil;& atilde;o. Ambas as caracter & iacute;sticas macrosc & oacute;picas ou microsc & oacute;picas foram examinadas incluindo cor, sensa & ccedil;& atilde;o, dire & ccedil;& atilde;o microfibilar, esp & eacute;cies de cristais e an & aacute;lises de se & ccedil;& otilde;es transversais. Uma cole & ccedil;& atilde;o de refer & ecirc;ncia f & iacute;sica e digital foi criada para compara & ccedil;& atilde;o. Oito amostras de fibras retiradas de seis objetos hist & oacute;ricos da cole & ccedil;& atilde;o do NMAI foram ent & atilde;o examinadas para testar a efic & aacute;cia do protocolo de testes de identifica & ccedil;& atilde;o de fibras liberianas. Traduzido por Sandra Baruki. Muchos de los textiles producidos por las culturas nativas americanas de los Woodlands est & aacute;n hechos de fibras de l & iacute;ber (floema) de plantas norteamericanas. Aunque las fibras de l & iacute;ber son f & aacute;ciles de identificar al microscopio, determinar la especie exacta ha sido un reto durante mucho tiempo. Hist & oacute;ricamente, las fibras de l & iacute;ber de las comunidades nativas americanas se han denominado "ca & ntilde;amo indio", un t & eacute;rmino confuso en el mejor de los casos. Este proyecto, emprendido en el National Museum of the American Indian (NMAI) (Museo Nacional del Ind & iacute;gena Americano) y financiado en parte por una beca de la Fundaci & oacute;n Andrew W. Mellon, se centr & oacute; en un enfoque combinado, trabajando tanto con miembros de la comunidad como con cient & iacute;ficos para proporcionar un trasfondo cultural de estas importantes fibras, as & iacute; como herramientas de diagn & oacute;stico & uacute;tiles para su identificaci & oacute;n. Se examinaron las caracter & iacute;sticas macrosc & oacute;picas y microsc & oacute;picas, como el color, el tacto, la orientaci & oacute;n microfibrilar, las especies de cristales y el an & aacute;lisis de secciones transversales. Se cre & oacute; una colecci & oacute;n de referencia f & iacute;sica y digital para su comparaci & oacute;n. Se examinaron ocho muestras de fibras tomadas de seis objetos hist & oacute;ricos de la colecci & oacute;n del NMAI para comprobar la eficacia del protocolo de identificaci & oacute;n de fibras l & iacute;ber. Traducci & oacute;n y revisi & oacute;n: Amparo Rueda e Irene Delaveris.

ReSUMeDans le but de donner des informations detaillees sur le depoussierage de la suie, une etude comparant le nettoyage du noir de fumee, servant de modele pour la suie, sur trois types de papiers de differentes rugosites est presentee. L'efficacite de dix materiaux de nettoyage de surface a sec - qui incluent des eponges, des gommes dures ou de mie de pain, de la gomme en poudre, une pate nettoyante, un elastomere de polydimethylsiloxane sans solvant et un coton-tige sec - a ete evaluee a l'aide d'un spectrophotometre portatif et de l'analyse visuelle de photographies prises sous microscope. L'observation des substrats nettoyes a l'aide d'un microscope optique portable a revele des informations detaillees sur la maniere dont les proprietes physiques des materiaux de nettoyage influencent la localisation des residus de suie sur la surface. La microscopie numerique 3D a ete utilisee pour evaluer les changements physiques de la surface du papier et la spectroscopie infrarouge a transformee de Fourier a ete utilisee pour identifier de potentiels residus des materiaux de nettoyage. Les resultats de cette etude ont ete compares avec des nettoyages ponctuels realises sur une couverture de livre endommagee par le feu. L'acces limite aux laboratoires de recherche durant le confinement de la pandemie de COVID-19 a oriente l'etude vers des methodes de recherche appliquee abordables pouvant etre faites en dehors des laboratoires, dont les details sont notes dans l'ensemble de l'article. Traduit par Sophie Barbisan. RESUMOPara fornecer informacao detalhada para ajudar os conservadores a lidar com a remocao de fuligem, e apresentada uma pesquisa que compara a remocao de pigmento preto de lampada, que serve como padrao de fuligem, de tres amostras de papel de rugosidades diferentes. A eficacia de dez materiais diferentes para a limpeza das superficies - incluindo esponjas, borrachas firmes e maleaveis, borracha ralada, um gel de limpeza, um elastomero de polidimetilsiloxano sem solvente e um cotonete ou swab seco - foram avaliados usando um espectrofotometro de cor portatil e analise de imagem de fotomicrografias. A inspecao de substratos higienizados com o uso de um microscopio otico portatil revelou informacao detalhada sobre como as propriedades fisicas de materiais de limpeza influenciam a localizacao do residuo de fuligem na superficie. A microscopia de luz digital 3D e a espectroscopia de infravermelho com transformada de Fourier foram utilizadas para avaliar alteracoes fisicas na superficie do papel e identificar possiveis residuos dos materiais apos a limpeza, respectivamente. Os resultados deste estudo modelo foram comparados com testes de limpeza pontual realizados em uma capa de livro danificada em incendio. O acesso limitado aos espacos de laboratorio durante o periodo de isolamento do COVID-19 motivou esta pesquisa a se concentrar nas maneiras acessiveis de realizar pesquisas tecnicas praticas fora do laboratorio, cujos detalhes sao observados ao longo deste artigo. Traduzido por Sandra Baruki. RESUMENCon el fin de proporcionar informacion detallada para ayudar a los conservadores que se enfrentan a la eliminacion del hollin, se presenta un estudio en el que se compara la eliminacion de negro de humo, que sirve como modelo de hollin, de tres muestras de papel de diferente rugosidad. Se ha evaluado la eficacia de diez materiales diferentes de limpieza de superficies en seco - incluyendo esponjas, gomas de borrar firmes y amasadas, migas de goma de borrar, una masilla de limpieza, un elastomero de polidimetilsiloxano sin disolventes y un hisopo seco - utilizando un espectrofotometro de color portatil y el analisis de imagenes de fotomicrografias. La inspeccion, de los sustratos limpiados, con un microscopio optico portatil revelo informacion detallada sobre como las propiedades fisicas de los materiales de limpieza influyen en la localizacion del hollin residual en la superficie. Se utilizaron la microscopia de luz digital 3D y la espectroscopia infrarroja transformada de Fourier para evaluar los cambios fisicos de la superficie del papel y para identificar los posibles residuos de los materiales despues de la limpieza, respectivamente. Los resultados de este estudio modelo se compararon con las pruebas de limpieza puntual realizadas en una cubierta de libro de papel danada por el fuego. El acceso limitado a los espacios del laboratorio durante el cierre por COVID-19 motivo que esta investigacion se centrara en formas asequibles de realizar investigaciones tecnicas practicas fuera del laboratorio, cuyos detalles se senalan a lo largo de este documento. Traduccion: Vera de la Cruz; revision: Ramon Sanchez, Amparo Rueda.

The demystification of how 19th-century novelly designed materials became significant elements of modern technological, economic, and cultural life requires a complete understanding of the material dimensions of historical artifacts. The objects frequently described as the earliest manufactured plastic products-the billiard balls made by John Wesley Hyatt and his associates from the late 1860s-are examined closely for the first time and are found to be more complex and functionally more successful than has been described. Modern analytical techniques such as optical microscopy, scanning electron microscope-energy dispersive X-ray spectroscopy, X-ray fluorescence, micro-Fourier transformed infrared, and handheld/micro-Raman spectroscopies were used to reveal the complex composition of the Smithsonian Institution's "original" 1868 celluloid billiard ball. Comparisons with billiard and pool balls commercialized from the 1880s to the 1960s showed an unexpected consistency in material formulations. All specimens were made of an unprecedented composite material prepared with a mixture of cellulose nitrate, camphor, and ground bone; the source of the bone was identified as cattle by peptide mass fingerprint (ZooMS). Patent specifications and contemporary journal descriptions explained how and when these formulations emerged. Combining the technical analyses of compositions with a careful reading of the historical record and contemporary descriptions reveals the key elements of the first successful efforts to substitute materials to assist the survival of endangered animals.

The Smithsonian Institution's National Museum of American History houses the largest remaining collection of inter-positive composite glass plate images from the production of Eadweard Muybridge's Animal Locomotion series. These photographs, which are approximately 150 years old, exhibit a wide range of degradation phenomena and products, including alteration of the glass plates. Compositions of both the image-bearing glass plates and support glass panels were obtained through quantitative scanning electron microscope-energy-dispersive spectrometry. Electron imaging of cross-sectioned samples of the image-bearing glass plates reveals a visible sodium-depleted glass alteration layer. Furthermore, electron imaging shows delamination of the image-containing gelatin layer and captures evidence that suggests that interfacial stresses between the glass alteration layer and the unaltered glass contribute to the delamination of this layer along with the overlaid gelatin.

Journal Article Quantitative and Qualitative Correlation of CL and X-ray Signals in Cr-bearing Jade from Chichén-Itzá Archaeological Zone, Mexico Get access Edward P Vicenzi, Edward P Vicenzi Smithsonian Institution, Museum Conservation Institute, Suitland, MD, USA Corresponding author: vicenzie@si.edu Search for other works by this author on: Oxford Academic Google Scholar Thomas Lam, Thomas Lam Smithsonian Institution, Museum Conservation Institute, Suitland, MD, USA Search for other works by this author on: Oxford Academic Google Scholar Heather A Lowers, Heather A Lowers U.S. Geological Survey, Denver, CO, USA Search for other works by this author on: Oxford Academic Google Scholar Paul K Carpenter, Paul K Carpenter Washington University, Department of Earth and Planetary Sciences, St. Louis, MO, USA Search for other works by this author on: Oxford Academic Google Scholar David T Adams David T Adams The University of Auckland, Faculty of Science, Auckland, NZ Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 656–660, https://doi.org/10.1017/S1431927622003142 Published: 01 August 2022

RESUMEN La Coleccion de historia fotografica del Smithsonian's National Museum of American History (Museo Nacional de Historia Estadounidense del Smithsonian) alberga la mayor coleccion de placas fotograficas de vidrio de la serie Animal Locomotion de Eadweard Muybridge. Estas imagenes son el antecesor inmediato de las imagenes en movimiento y sirven como una herramienta de investigacion invaluable para comprender el proceso y el lugar de Muybridge en la historia de la fotografia. Como parte de un relevamiento del estado de esta coleccion, se realizo el analisis de los materiales y productos de deterioro encontrados en las placas. Este documento se centra en las observaciones realizadas durante el analisis de la capa de emulsion de gelatina portadora de imagenes de estos objetos, ya que el deterioro y la perdida de esta capa es lo que mas compromete la identidad y el significado de los objetos mismos. El analisis se realizo en placas de imagenes y fragmentos que se han desvinculado de sus paneles compuestos originales. Los resultados de los analisis incluyeron: la identificacion de la gelatina y los materiales formadores de imagenes, nueva informacion sobre los procesos fotograficos utilizados en la produccion de estas placas, a saber, el uso de intensificacion con mercurio y conocimientos significativos sobre los diversos mecanismos de deterioro encontrados en estas placas incluyendo espejo de plata, danos por agua y agrietamiento de la gelatina, que amenazan la estabilidad a largo plazo de esta coleccion. Traduccion: Amparo Rueda. ReSUMe La Photographic History Collection du National Museum of American History de la Smithsonian comprend la plus grande collection de plaques photographiques sur verre de la serie Animal Locomotion d'Eadweard Muybridge. Ces images precedent de pres les images animees et servent d'outil central dans la comprehension du procede de Muybridge, ainsi que la place de ce dernier au sein de l'histoire de la photographie. Lors d'une etude de la collection, des analyses des materiaux et des produits de degradations trouves sur les plaques ont ete entreprises. Cet article se concentre sur les observations faites durant l'analyse de la couche image de gelatine de ces objets, sachant que l'alteration et la perte de cette couche est la plus compromettante concernant l'identite et la pertinence de ces objets. Les analyses ont ete faites sur des plaques photographiques ainsi que sur des fragments dissocies de leurs panneaux composites. Les resultats de ces analyses comprennent : l'identification de la gelatine et des materiaux formant l'image, de nouvelles informations sur les procedes photographiques employes durant la creation de ces plaques, en particulier l'utilisation de l'intensification au mercure, ainsi que d'importantes observations quant aux processus de degradation varies trouves sur ces objets comme le miroir d'argent, les degats des eaux et les craquelures de la gelatine, qui mettent en peril la stabilite a long terme de cette collection. Traduction par Sophie Barbisan. RESUMO A Colecao de Historia Fotografica do Museu Nacional de Historia Americana do Smithsonian abriga a maior colecao de placas fotograficas de vidro da serie Animal Locomotion de Eadweard Muybridge. Essas imagens sao o antecessor imediato do cinema (imagens moveis) e servem como uma ferramenta de pesquisa inestimavel para entender o processo e o lugar de Muybridge na historia da fotografia. Como parte de um levantamento da condicao desta colecao, foi realizada a analise dos materiais e produtos de deterioracao encontrados nas placas. Este artigo se concentra em observacoes feitas durante a analise da camada de emulsao de gelatina com rolamento de imagem desses objetos, pois a deterioracao e perda dessa camada e a mais comprometedora para a identidade e significado dos proprios objetos. A analise foi realizada em placas de imagem e fragmentos que se desassociaram de seus paineis compostos originais. Os resultados das analises incluiram: a identificacao dos materiais de formacao de gelatina e imagem, novas informacoes sobre os processos fotograficos utilizados na producao dessas placas, especificamente, o uso da intensificacao do mercurio, e insights significativos sobre os diversos mecanismos de deterioracao encontrados nesses objetos, incluindo espelhamento de prata, danos de agua e rachaduras na gelatina, que ameacam a estabilidade desta colecao a longo prazo. Traduzido por Beatriz Haspo.

Atomic layer deposited (ALD) amorphous aluminium oxide and titanium oxide coatings have been investigated for use in reducing the rate of silicate glass alteration. Mass spectrometric analysis of leachate from elevated temperature aqueous immersion alteration experiments showed a marked decrease in the concentration of released Na and Si from the glass when the vitrified material was ALD coated as compared to uncoated glass. This decrease is consistent with the proposed protective effect of the ALD coating. Additionally, visual observations indicate formation of significant amounts of amorphous, secondary phase sediment for immersed, uncoated glass. This sediment was not present in the solution of the ALD coated and altered glass samples. However, the ALD coating did delaminate after protracted immersion, a likely limiting factor of the efficacy of ALD coatings. This limitation may be mitigated through a proposed refinement of the ALD coating procedure.

Dark and clear silicate glasses formed during an iron age vitrification event ≈ 1500 years ago at the Broborg hillfort near Uppsala, Sweden have been analyzed using a scanning electron microscope equipped with a micro-X-ray fluorescence (μXRF) spectrometer. Correlated µXRF and electron beam-induced energy dispersive spectrometry (EDS) X-ray maps were collected via stage-scanning at constant velocity. This coupled procedure represents a new approach for the cultural heritage community to conduct analytical studies of archaeometric specimens composed of metal, ceramic, or mixed inorganic/organic materials, where major and trace element compositions are registered in space for areas up to the centimeter-length scale at micrometer-scale resolution. Overview images were used to select areas for EDS beam scan maps correlated with multispectral cathodoluminescence (CL) imaging and co-located quantitative EDS and μXRF point analysis. Fe, Ca, Mg, Ti, P, Mn, Zr, Zn, and Y are enriched in the dark glass, while Si, Al, K, Na, Ba, Sr, Rb, and Ga are enriched in the clear glass. Unmelted material is comprised predominately of quartz (SiO 2 ) along with trace apatite (Ca 5 (PO 4 ) 3 [Cl,OH]) and zircon (ZrSiO 4 ). Multivariate statistical analysis was used to measure the area fractions of high variance components while lower variance components represented phase mixtures. Differences between calculated melt viscosities for the glass compositions are consistent with field and laboratory observations. Coupled large area EDS and μXRF imaging shows significant promise for informed selection of higher spatial resolution and higher sensitivity follow-up studies, e.g., those performed using synchrotron analysis. Graphical Abstract

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X-ray fluorescence spectrometry (XRF) is commonly used as a non-destructive method to identify the geochemical source of obsidian artifacts. We examine in detail three decimeter-scale, polished obsidian "mirrors" housed in the Smithsonian Institution's (SI) National Museum of the American Indian (NMAI) collections that have previously had minor and trace element components analyzed by portable XRF. Two of the tablets have raw material provenance to the Ucareo source in Michoacan, Mexico, a location within the Los Azufres volcanic complex, while the source for the third tablet, made of mahogany (or meca) obsidian, remained unassigned. We provide a complete analysis of the major, minor, and trace element compositions for each tablet using co-located SEM-based energy dispersive X-ray spectrometry and micro-XRF spectrometry with fundamental parameters quantification. Source assignments for the tablets were made by comparing minor and trace element ratios to obsidian reference samples using canonical discriminant analysis. The reference specimens analyzed expand upon archaeological sources in Central Mexico relevant during Colonial times and include new data for obsidian locations within the Los Azufres complex. Our analyses confirm the previous source assignment for Ucareo for the black tablets and indicate a geochemical match for the mahogany obsidian from a nearby location within the Los Azufres complex that has not previously been associated with archaeological artifacts. Finally, we provide a detailed comparison of the portable and micro-XRF methods and discuss disparities in data and their implications.

A new standards-based scanning electron microscopy with the energy-dispersive X-ray spectrometry (SEM-EDS) quantification method was used to analyze the thin-film coating of an 18th century French textile decorated with metal threads in variable pressure conditions. This analytical technique can allow for nondestructive quantitative characterization of the near surface of cultural heritage objects small enough to be placed in an SEM chamber that may contain corrosion products, without applying a conductive coating. A multivoltage analysis consisting of measurements taken at a series of electron beam energies was obtained and input into a film thickness and composition (FTC) computational model to characterize a layered Au on Ag reference material, in addition to a historic metal thread. Using the FTC computation, the thread coating was determined to be an alloy ≈ 80% Au 20% Ag on a nominally pure Ag substrate, and this composition matches a minimum gold standard allowed for goods around the time of manufacture. The computed gilding thicknesses range from single digit nm to 300 nm depending upon surface inhomogeneities formed during the production of the thread. Interaction volumes and X-ray spectra generated by Monte Carlo modeling are consistent with the measured gilding thicknesses and compositions. Validation of the FTC-computed gilding composition and thickness variations were obtained by cross-sectional analysis.