Emeralds from Colombia are among the most highly-prized and valuable gemstones. Their growth phenomena including information about the geology of the area were described in detail by Pig-natelli et al. (2015, 2022) and Schmetzer and Martayan (2023). Here, we present data obtained by scanning electron microscopy (SEM), electron microprobe analysis (EMPA), and infrared absorption spectroscopy (IR) for five emerald crystals. The surface of the crystals shows both, growth phe-nomena as well as dissolution phenomena, the latter as etch pits (EP). Such EP have been used previously for other beryl types, mainly from pegmatitic environments (Kurumathoor and Franz, 2018); the Colombian emeralds come from low-grade metamorphosed black shales and thus offer the possibility to extend the use of EP as a provenance indicator to other types of beryl deposits. Internal structures are manifested in chemical zoning, investigated by EMPA and micro-X-ray fluo-rescence (µXRF). The crystals are characterized chemically by EMPA, polarized IR spectroscopy of oriented crystals showed the presence of fluids in the channels of the beryl structure.
Black opal is a rare variety of opal-CT, which is pigmented by organic matter (OM) and can therefore be considered as an example of geo-bio interaction (Gouzy et al., 2025). The locality of Volyn, Ukraine with its famous chamber pegmatites is well-known for interaction between OM and igneous rocks (Franz et al., 2017). The locality was recently renamed Khoroshiv, but because in the geological-mineralogical literature the name Volyn was introduced, we use this name here. The intrusion of the pegmatites is closely connected to the intrusion of the host rocks, granites of the southwestern part of the Korosten Pluton, and the intrusion age was determined as 1.76 Ga (Shumlyanskyy et al., 2021). OM was identified as kerite (fossilized remains of organisms; Franz et al., 2023, and references therein), and in fluid inclusions in beryl and topaz (Vozniak et al., 2012; Vozniak and Pavlyshin, 2008). Furthermore, formation of NH4-bearing feldspar (buddingtonite) and muscovite (tobelite) in breccia (identified together with the pegmatites) point to the interaction between decayed OM and the igneous minerals (Franz et al., 2017). The timing of the interaction between OM and igneous (and other) fluids is an important question (Franz et al., 2024), and therefore we also give age constraints on the formation of the black opal, which from textural arguments seems to be one of the latest mineral formations.
We give detailed information about the sample sites, the macroscopic features of the samples of different types of opal, and the analytical procedures. The description of the black opal samples is presented in images from secondary electron microscopy (SEM), back-scattered electron images (BSE) obtained with by electron microprobe (EMPA), element distribution maps obtained by µXRF (X-ray fluorescence), Fourier-transformed infrared spectroscopy (IR), and X-ray powder (XRD) characterization.
Chemical analyses were obtained by wave-length dispersive (WDS) analyses with the EMPA as well as by energy-dispersive (EDX) analyses with both the SEM and the EMPA instruments, to identify and characterize inclusions in the black opal. Trioctahedral Li-mica (polylithionite) is included by opal in one sample, and because this type of mica has not been described in detail from the Volyn peg-matites, we present the EMPA analytical data here in detail.
The presence of OM, which is known to absorb U in sufficient amounts, allows dating by the U-Pb decay system. The results of the isotopic dating with the laser-ablation sector-field inductively-coupled mass spectroscopy system (LA-SF-ICP-MS) is presented for the selected individual do-mains in three samples. The operating conditions are summarized in a separated pdf document.
The soil state factors climate and time are of growing interest in respect to landscape and consequently soil evolution. Climate change can have significant impact on the global biogeochemical cycle by altering the type and rate of soil processes and the resulting soil properties. Direct and dramatic ecological responses to this impending warming are expected. Climatic warming is thought to increase soil temperature and to change many critical factors in plant productivity, phenology and succession. A main unknown parametre is the reactivity of soils and the rate of reactions. - Consequently, a soil sequence along an elevational gradient ranging from subtropical to subalpine climate zones in the Etna region (Sicily, southern Italy) are investigated in respect of organic C, kaolinite and crystalline to non-crystalline Al- and Fe-phases. Special emphasis is given to the stabilization of soil organic carbon (SOC) and its interaction with the inorganic phases. Furthermore, a weathering sequence with soils developing on volcanic, trachy-basaltic parent materials with ages ranging from 100 - 115000 years in the Etna region serve as the basis to analyse and calculate the accumulation and stabilisation mechanisms of soil organic matter (SOM), the transformation of pedogenic Fe and Al, the formation and transformation of clay minerals, the weathering indices and, by means of mass-balance calculations, net losses of the main elements.