A multi-technique approach has been proposed to characterize weathering phases and their relationships with the primary rhyolitic paragenesis at Piloni di Torniella (Tuscany, Italy) hydrothermal kaolin mine. Analyses were carried out on geological samples and on material extracted from the mine for assessment of the ceramic application of the raw material. A multi-technique protocol was applied, involving both bulk techniques (e.g. X-ray powder diffraction) and microanalytical techniques (e.g. petrographic analysis, scanning electron microscopy with energy-dispersive spectrometry and micro-Raman spectroscopy), including imaging applications. Some secondary phases, such as alunite, halloysite and α-cristobalite, were identified and characterized. Highlighting the presence of such phases is important for the mine license holder and traders, who should manage the specific properties of the final commercial mine products for ceramic applications. Furthermore, a better understanding of the alteration mechanism of biotite at the study site was achieved; in fact, where the alteration process is complete, both kaolinite and halloysite have been identified as intergrown phases in biotite pseudomorphs. This suggests the presence of a lower-temperature fluid (<100°C) percolating in some areas of the mine, probably representing a different alteration stage than that which led to the kaolinization.

Este trabajo se propone avanzar en la comprensión de los procesos históricos de pintado del sitio arqueológico de Oyola (Sierra El Alto-Ancasti, Catamarca, Argentina). En particular, se evalúan similitudes y diferencias en la composición material de las mezclas pigmentarias para entrever la existencia de antiguas recetas pictóricas en la confección de las pinturas rupestres negras. Para ello se realizaron análisis microestratigráficos de 28 motivos mediante microscopía electrónica de barrido con análisis elemental por espectroscopía dispersiva en energía de rayos X (MEB-EDS), y microespectroscopía Raman (RS). Su estudio comparativo señaló el uso alternativo de dos pigmentos negros (carbón vegetal y óxidos de manganeso) combinados, en algunos casos, con un aditivo (sulfato de calcio). De esta forma, fue posible conocer ciertos aspectos de las recetas pictóricas que orientaron la preparación de las mezclas pigmentarias negras, aproximándonos a algunas de las tradiciones y saberes retomados. Para alcanzar una comprensión histórica de dichas recetas, se evaluó la distribución espacial, temporal y algunas características formales de los motivos rupestres realizados con ellas. Al no identificarse tendencias claras, se propone una definición menos normativa de receta pictórica que resalta los aspectos compartidos entre distintos episodios de pintado sin perder de vista las posibilidades creativas de cada evento.

Lacquerwork technologies comprise multiple techniques depending on countries, time, and traditions. Carved Asian lacquers applied on wooden objects consist of multiple thin uncolored or pigmented layers spread over the surface. To radiocarbon (14C) date these types of objects, often only the wooden structure is used. Here we report on a set of carved lacquered objects that were dated based on stylistic form, 14C dating of the wooden structure and of the Asian lacquers. THM-Py-GC-MS and micro-Raman spectroscopy were used to confirm the molecular composition of the lacquers and helped assessing the pretreatment protocol. The lacquers analyzed contained between 20 and 50% wt carbon, thus 2–5 mg of sample were necessary for 14C dating. The dates obtained on wood and lacquers showed a reliable correlation. The results suggest that, in most cases, it is sufficient to sample a part of the lacquer layers to date an object. We advise to perform an acid pretreatment followed by a successive solvent immersion with an increasing polarity. Dating different components of a lacquered object can also help to understand previous restoration interventions that frequently occur for ancient lacquered objects. Ceramic, metallic, and other objects covered with Asian lacquers can also be dated using this approach.

Parahibbingite [β-Fe2(OH)3Cl], a new mineral recently described from ultramafic rocks in the Bushveld Complex, South Africa, has been found to form millimetric well-developed crystals as a terrestrial weathering product of the Muonionalusta iron meteorite. The mineral, initially identified by means of Raman spectroscopy, was found in a small cavity within a crust of rust on a granitic rock fragment that was in direct contact with the alteration crust of a meteorite specimen, collected in the Kitkiöjärvi area, Sweden. Its crystal structure was refined from single-crystal X-ray diffraction data (R1 = 0.0331) in the space group R$\bar{3}$m [a = 6.9362(4), c = 14.673(1) Å and V = 611.35(7) Å3 for Z = 6], thus confirming the structural model of synthetic β-Fe2(OH)3Cl. It consists of a network of octahedrally coordinated Fe2+ atoms alternately arranged in triangular and Kagomé layers, stacked along the c axis. The H atom position was determined, showing O–H⋅⋅⋅Cl bonds, which provides a further link between layers. Parahibbingite is found to be not only an important constituent of the corrosion system of archaeological iron artefacts but can also play an important role as an alteration product of iron meteorites.