Volume 109, Issue 9

Germanium (Ge) is a critical raw material for emerging high-tech and green industries, resulting in considerable recent interest in understanding its distribution and geochemical behavior in ore deposits. In this contribution, the distribution of Ge and related trace elements in the Fule Pb-Zn(-Ge) deposit, South China, is investigated to reveal the distribution of Ge in the hydrothermal ores and during sulfide weathering, using multiple microanalytical techniques, including scanning electron microscopy, electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In the Fule MVT deposit, sphalerite (ZnS) is the most significant Ge-carrier relative to other sulfides, though the five recognized textural types of sphalerite display progressive depletion in Ge from the first sphalerite generation to the late one. In the early stage, sphalerite with fine-grained chalcopyrite inclusions has the highest Ge concentrations, probably accounting for a significant proportion of the total Ge. We interpret that high Ge concentrations in the early sphalerite may be attributable to high Cu activity in the mineralizing fluids. During oxidative weathering, Ge was redistributed from its original host, sphalerite, to the weathering product willemite (Zn 2 SiO 4 ) rather than smithsonite (ZnCO 3 ), with high levels of Ge (up to 448 μg/g) present in the willemite. The formation of abundant willemite largely prevents the dispersion of Ge during weathering. In principle, willemite-hosted Ge should be fully recoverable, and the Zn-silicate ores may, therefore, be a potential target to meet future demand. This study provides new information on how Ge behaves from sulfide- to weathering-stage in MVT systems, which directly impacts Ge mobility and deportment changes and the development of metallurgical strategies for Ge recovery.

Erionite is the name for a zeolite mineral series originating from diagenesis or hydrothermal alteration of volcanic rocks. The particular erionite “species” is based on the dominant extra-framework cation, erionite-Ca, erionite-K, or erionite Na. Irrespective of the species, erionite can display a fibrous/asbestiform morphology and has been linked with cases of malignant mesothelioma, a disease typically associated with asbestos exposure. Characterization of new discoveries of erionite is therefore important to assess any potential exposure hazards. This study describes a new asbestiform erionite from vesicles within the Upper Cretaceous Mt. Somers Volcanics Group (MSVG), Canterbury, New Zealand. The erionite is within the Hinds River Dacite, the youngest unit within the MSVG at Gawler Downs, ~100 km west of Christchurch, in the foothills of the Southern Alps. A multi-analytical approach was taken to analyze the sample which included micro-Raman spectroscopy, thermogravimetric analysis, electron microscopy, electron microprobe analysis, and X-ray powder diffraction with the Rietveld method. Results confirmed the mineral as fibrous erionite-K. The chemical composition of the mineral is unique due to the presence of higher levels of Mg. While Fe was also identified, this was due to smectite flakes occurring on the surface of the erionite fibers. According to the World Health Organization (WHO) respirable mineral fiber definition, where length ≥5 μm. width ≤3 μm, and aspect ratio (L/w) ≥3:1, the Gawler Downs erionite fibers are respirable, while the fibers themselves exceed respirable thickness. In addition to morphology, a value for the potential toxicity model was computed to be 2.28 for the Gawler Downs erionite. This is similar to those of other carcinogenic erionites from Karain, Turkey (2.33), and Nevada, U.S.A. (2.28). Taken together, results indicate Gawler Downs erionite represents an environmental hazard. Nevertheless, further investigation is required to determine potential environmental exposure pathways by which erionite may become airborne and assess the actual environmental risk in the Gawler Downs area.

The first widespread occurrence of rare Na-, Ca-, and Mg,Mn,Fe-bearing phosphate chladniite was observed in meteorite Graves Nunataks (GRA) 12510, which is a primitive achondrite that sits within the winonaite class. Numerous 1–500 μm chladniite grains were found, often on the margins between silicate clasts and the kamacite portions of the large metal veins that permeated through the sample. The largest chladniite grains are associated with merrillite, kamacite, taenite, troilite, albite, forsterite, diopside, and enstatite, with a few tiny chladniite grains and an apatite grain enclosed within merrillite. GRA 12510s average chladniite composition is Na 2.7 Ca 1.25 (Mg 10.02 Mn 0.69 Fe 0.20 ) Σ10.91 (PO 4 ) 9 . Electron backscattered diffraction (EBSD) patterns indicate varying degrees of nucleation and growth of chladniite grains. Additionally, the first pure Raman spectrum of chladniite is described here, revealing primary ν 1 bands at 954, 974, and especially 984 cm –1 . The co-occurrence and close association of merrillite, apatite, chladniite, and P-bearing metallic phases within GRA 12510 suggests that the f O 2 of IW-2 to IW-4 is an intrinsic property of the precursor chondritic material, and the phosphate-phosphide reaction may have buffered the final winonaite and IAB iron meteorite phase assemblages. Altogether, chladniite appears to form alongside other phosphates, with their chemistries reflecting the diverse environment of their formation. Meteoritic chladniite likely formed through subsolidus oxidation of schreibersite, scavenging Na from albite, Ca from diopside, Mg from enstatite/forsterite, Fe from kamacite/taenite, and Mn from alabandite/chromite when available. A P 0 -P 5+ redox-buffered environment also has implications for thermometry and fast cooling rates, although more experiments are needed to extrapolate powder reaction rates to those of larger crystals. Furthermore, phosphide-phosphate buffered experiments may aid in investigating equilibrium chemistry at f O 2 values between IW-2 and IW-4, which have been challenging to explore experimentally due to the limited availability of solid metal-metal oxide buffers between IW (Fe-FeO) and IW-5 (Cr-Cr 2 O 3 ) at temperatures and pressures relevant to planetary interiors. Future investigations of phosphide-phosphate redox-buffered genesis at f O 2 values between IW-2 and IW-4 have important implications for primitive meteorite constituents (e.g., CAI values), partially differentiated planetesimals and planets, including Mercury and core formation on Earth.

Controlling factors of potassium (K) isotopic fractionation in K-feldspar remain poorly constrained. In this study, we analyzed the K isotopic compositions of 11 K-feldspar samples from diverse lithological compositions. The degree of Al/Si order ranged from 0.22 to 0.94 (1.0 = completely ordered). Analyzed samples are mixtures of K-feldspar (>70 wt%) and coexisting albite. The relative contribution of K 2 O from the K-feldspar phase of the sample was over 98%, indicating that the K isotopic composition (δ 41 K) derives mainly from K-feldspar and hence reflects its behavior. The δ 41 K values of these samples range from –0.710 to –0.075‰, which are slightly correlated with the degree of Al/Si order. The correlations of δ 41 K with SiO 2 and Al 2 O 3 contents and the corresponding Al/Si mole ratios reveal that Al and Si play a significant role in the K isotopic behavior of K-feldspar. The correlations of δ 41 K with SiO 2 and Al 2 O 3 contents are attributed to the difference in K-O bond strengths. Compared to K-feldspar, the K content could be a better proxy for constraining the δ 41 K of plagioclase. Our results demonstrate that the δ 41 K of K-feldspar is dependent on its mineral chemistry, and its K isotopic composition may be insensitive to other factors, such as the source heterogeneity. The inference is further confirmed by comparing the δ 41 K values in this study with published δ 41 K values of K-feldspar from different sources.

The source of sulfuric acid and associated aqueous alteration of ancient martian sedimentary rocks remain under debate in the context of divergent models of jarosite formation. Here, we report the formation of sulfates, including jarosite in K-bentonites within shallow-water facies of the Permian-Triassic (P-T) transition at Xiakou in South China. In these strata, jarosite is dispersed in the clay matrix or forms aggregates in pore spaces, has a euhedral morphology, and coexists with variably 34 S-depleted paragenetic gypsum and bassanite (δ 34 S = –37.23‰ to +3.20‰ VCDT). Subaqueous alteration of volcanic tuffs concurrently with oxidation of upwelled, biogenically sourced H 2 S is the process of jarosite formation in the Xiakou K-bentonites. This mechanism of jarosite precipitation and stability over geological time challenges the long-held view of acidic, water-limited conditions leading to iron(III) sulfate precipitation and would be consistent with possible microbial or nanobial life on early Mars.

Elucidating the high-temperature behavior of rock-forming minerals such as amphiboles (AB 2 C 5 T 8 O 22 W 2 ) is critical for the understanding of large-scale geological processes in the lithosphere and, in particular, the development of high conductivity in the Earth’s interior. Recently, we have shown that at elevated temperatures, C Fe-bearing amphiboles with a vacant A site develop two types of charge carriers: (1) small polarons and (2) delocalized H + ions. To elucidate the effect of A -site cations on the formation and stability of charge carriers within the amphibole structure, here we analyzed synthetic potassic-ferro-richterite as a model Fe-rich amphibole with a fully occupied A site via in situ temperature-dependent Raman spectroscopy. We further compare the results from in situ time-dependent Raman-scattering experiments on pre-heated and rapidly quenched potassic-ferro-richterite and riebeckite as a model Fe-rich amphibole with a vacant A site. We show that the presence of A -site cations (1) reduces the activation temperature of mobile polarons and delocalized H + cations; (2) decreases the magnitude of the polaron dipole moment; (3) slows down the process of re-localization of electrons on cooling; and (4) makes the electrons inert to rapid change in external conditions, supporting the persistence of a metastable state of pre-activated delocalized electrons even at room temperature. Our results have important geological implications demonstrating that the A -site cations may control the depth of development of high conductivity in subducted amphibole-bearing rocks. Moreover, from the viewpoint of mineral-inspired materials science, our results suggest that the amphibole-structure type has great potential for designing functional materials with tunable anisotropic-conductivity properties.

Uranyl sulfate minerals are the most rapidly expanding group of uranium minerals, with dozens of species described in the past decade from the localities of White Canyon, U.S.A. and Jáchymov, Czech Republic. Synthetic analogs of a suite of uranyl sulfate minerals were crystallized, characterized, and the standard-state enthalpies of formation ( Δ Hf∘ $\begin{array}{} \displaystyle \Delta H^{\circ}_{\text{f}} \end{array}$) were determined. Synthetic lussierite is monoclinic, space group Cc , a = 9.2896, b = 28.685, c = 9.6155 Å, β = 93.504°. Synthetic geschieberite is orthorhombic, space group Pna 2 1 , a = 13.7408, b = 7.2713, c = 11.5844 Å. The standard-state enthalpies of formation from the binary oxides for lussierite, péligotite, shumwayite, geschieberite, and bluelizardite are –3214 ± 78, –2026 ± 33, –587 ± 22, –966.1 ± 10.9, and –2084 ± 21 kJ/mol, respectively, while the standard-state enthalpies of formation of each phase from its elements are –9743 ± 78, –7220 ± 33, –5255 ± 22, –3916 ± 20, and –7117 ± 21 kJ/mol, respectively. The Δ Hf∘ $\begin{array}{} \displaystyle \Delta H^{\circ}_{\text{f}} \end{array}$ of péligotite was accurately estimated using the Δ Hf∘ $\begin{array}{} \displaystyle \Delta H^{\circ}_{\text{f}} \end{array}$ of lussierite, bluelizardite, and literature values of the oxide components of each phase. This implies that estimates can be made accurately of the Δ Hf∘ $\begin{array}{} \displaystyle \Delta H^{\circ}_{\text{f}} \end{array}$ of uranyl sulfates of minerals without synthetic analogs.

Understanding the mineralization of coral is significant for the formation of coral reefs and paleoclimatic reconstructions. However, the fundamental mechanisms involved in biomineralization are poorly understood. A combination of Raman spectral and cross-polarized reflected light microscopy imaging was used to examine the three-dimensional spatial distribution of the skeletal ultrastructures and their associated mineral, organic, and water chemistry in coral, which enable insight into the spatial growth features of the ultrastructures and possible formation processes. A possible mechanism is proposed that controls the formation of skeletal ultrastructures, which likely involves compartmentalized calcifying cells and their related cellular activities. This could clarify the association between coral skeletal mineralization and biology, and it may be beneficial to better protection and application of coral reefs.

Natural carbonatites exhibit a wide range of high field strength elements (HFSEs) and the highest Nb/Ta and Zr/Hf ratios among various rock types. However, primitive carbonatitic melts derived from carbonated peridotite do not display significant fractionation of Nb-Ta and Zr-Hf. To investigate this further, we conducted liquid immiscibility experiments to comprehend the differentiation of these HFSEs. Our experiments revealed substantial changes in partition coefficients for Nb, Ta, Zr, and Hf between carbonatite and silicate melts. We identified a positive correlation between the partition coefficients of these elements and Si, indicating that Si determines the differentiation of Nb-Ta and Zr-Hf during liquid immiscibility. The partition coefficients of Si increase as temperature increases and pressure decreases, resulting in higher HFSE concentrations during the early stages of liquid immiscibility. Liquid immiscibility is crucial in differentiating HFSEs in carbonatitic melts, explaining the association between super large carbonatite-related Nb deposits and Si-undersaturated silicate rocks.

Accessory minerals like zircon, rutile and monazite are routinely studied to inform about the timing and nature of geological processes. These studies are underpinned by our understanding of the transfer processes of trace elements and the assumption that the isotopic systems remain undisturbed. However, the presence of microstructures or Pb-bearing phases in minerals can lead to the alteration of the Pb isotopic composition. To gain insight into the relationship between Pb isotopic alterations from inclusions and microstructures, this study focused on inclusions from an ultra-high-temperature metamorphic rutile. The studied inclusions are submicrometer monazites, a common mineral rich in Pb but normally not present in rutile. The sample is sourced from Mt. Hardy, Napier Complex, East Antarctica, an ultra-high-temperature (UHT) metamorphic terrane. By applying correlative analytical techniques, including electron backscatter diffraction mapping, transmission electron microscopy (TEM), and atom probe tomography, it is shown that monazite inclusions are often in contact with low-angle boundaries and yield no preferred orientation. TEM analysis shows the monazite core has a mottled texture due to the presence of radiation damage and nanoclusters associated with the radiation damage defects that are rich in U, Pb, and Ca. Some monazites exhibit a core-rim structure. The rim yields clusters composed of Ca- and Li-phosphate that enclose Pb nanoclusters that are only present in small amounts compared to the core, with Pb likely diffused into the rutile-monazite interface. These textures are the result of two stages of Pb mobility. Initial Pb segregation was driven by volume diffusion during UHT metamorphism (2500 Ma). The second stage is a stress-induced recrystallization during exhumation, leading to recrystallization of the monazite rim and trace element transport. The isotopic signature of Pb trapped within the rutile-monazite interface constrains the timing of Pb mobility to ca. 550 Ma.

Knowledge of the three-dimensional distribution of minerals in a rock sample is of fundamental importance to deciphering a sample’s properties and history. Attenuation-contrast X-ray computed tomography (X-ray CT) is widely used in the geosciences to determine the three-dimensional distributions of minerals or pores, or both. Photon counting CT (PC-CT) uses a novel energy-resolved X-ray detector that allows X-rays with a continuous energy spectrum to be detected separately within arbitrary energy ranges. Here we report the first results of applying laboratory-build PC-CT combined with multi-pixel photon counter (MPPC) to common minerals such as quartz and calcite. In the low-energy range, PC-CT produced higher contrast images than single-energy X-ray CT. Minerals were successfully identified from the relationships between the mean CT values for each energy window and the mean difference between pairs of energy windows. These results suggest that PC-CT can produce high-contrast images of minerals and may be able to distinguish mineral phases with different attenuation curves, even when their CT values are similar. We obtained CT images of minerals in a natural sedimentary rock sample, composed mainly of quartz and carbonate. Although the spatial resolution of the detector in this study was insufficient for the sample, the main carbonate veins were clearly visible as high carbonate-content areas in the PC-CT images. Given some prior knowledge of mineral phases from other methods, it may be possible to use PC-CT imaging to obtain further information about their chemical compositions.

GCDkit.Mineral is a platform-independent (Windows/Mac/Linux) freeware for recalculation, plotting, and statistical treatment of mineral data obtained by microbeam techniques, typically an electron microprobe. It is written in R, a language providing a feature-rich environment for statistics and data visualization. This new program imports compositional data in various commonly used file formats or retrieves them from the clipboard. Routines are available for data management, i.e., grouping, searching, and generation of subsets, using regular expressions and Boolean logic. Raw compositional data (wt%) are recalculated to atoms per formula unit (apfu) based on a required number of O equivalents, atoms, or charges, with or without Fe II /Fe III estimation by various methods. Analyses may then be recast to structural formulae, i.e., the atoms are distributed into appropriate crystallographic sites. For minerals forming solid solutions, the molar percentages of end-members are computed. All the data may be treated statistically, either by built-in functions for descriptive and multivariate statistics or using the wealth of tools provided by the wide R community. Raw and recalculated mineral data may be plotted on assorted binary and ternary plots and boxplots. Most are defined as internal templates that provide a means to make later changes to the plot (zooming and scaling, adding comments or legend, identifying data points, altering the size or color of the plotting symbols, etc.). The publication-ready graphics may be saved into several vector- (PostScript, PDF, and WMF) and bitmap-based (e.g., PNG, TIF, and JPG) formats, ready to be imported into a professional graphical, presentation, or desktop publishing software. Importantly, the graphical templates are used as a basis for classification. The general classification routine looks for the name of the polygon within the diagram (= graphical template), into which the analysis falls according to its x–y coordinates. The outcome may be either the name of a mineral or a link to another diagram in the case of more complex classification schemes. Following the rules of the International Mineralogical Association (IMA), in some cases, the classification is not done graphically but using prescribed algorithms. The class mechanism in R provides an elegant solution to the computational problems presented by the differing requirements of each mineral group. By assigning each mineral species to a particular class, all algorithms may be implemented as mutually independent but mineral group-specific methods. The default recalculation options for each mineral class are stored externally in a small and simple text file. The program is designed to cater to three potential user groups. For users with no familiarity with R, the program is fully menu-driven and contains embedded default recalculation options for many common rock-forming minerals. More experienced users may easily tweak these parameters, as they are saved in a logically structured plain text file. Seasoned R users may invoke GCDkit.Mineral in command line mode, use batch scripts or Python-driven notebooks (e.g., of project Jupyter), or modify and develop new recalculations or plugins. The lucid, open, and modular design thus makes GCDkit.Mineral a versatile workbench for everyday use, as well as a promising platform for community-driven development. The GCDkit family of R tools, including GCDkit. Mineral, is distributed through the WWW. The current version may be downloaded from http://mineral.gcdkit.org.

Apatite is an accessory phase in all the units of the internally zoned Berry-Havey complex pegmatite. This body presents a highly fractionated core zone, enriched in Li, F, B, Be, and P, which hosts three different types of pockets, some of them often containing tens to hundreds of gemmy euhedral Li-rich tourmaline crystals, together with other mineral phases such as lepidolite. Processes involved in the complex internal evolution of pegmatitic melts that give rise to zoned bodies containing pockets are not completely understood. To shed light on these processes, apatite from all the different units of the Berry-Havey pegmatite (wall zone, intermediate zone, core margin, and core zone pods) and from the three pocket types (Li-poor, Li-rich, and apatite seams) has been characterized petrographically and later analyzed for major (electronic microprobe) and trace elements (LA-ICP-MS). Results indicate that apatite chemistry changed significantly during the crystallization of the Berry-Havey pegmatite, reflecting the conditions at each stage and mainly depending on the fractionation degree, f O 2 , and paragenetic association. Fluorapatite is found in all the units except the core margin, the Li-poor pockets, and the seams, where Mn-bearing fluorapatite is present. A gradual increase of the Mn content in apatite from the pegmatite border (wall zone) inward, up to the formation of subrounded masses of Mn-Fe phosphate in the core zone pods, parallels the increasing fractionation of the melt. Phosphate crystallization would deplete the residual melt in Mn, probably causing the significant Mn-decrease observed in apatite from the core zone pods and Li-rich pockets. The late depletion of Mn could also be related to an increase of f O 2 in the melt during the later stages of its evolution. Main trace element variations in apatite at both pegmatite and crystal scales correspond to REE, Y, and Sr. Yttrium and REE behave in a very similar way, decreasing inward, i.e., with fractionation of the pegmatitic melt (ΣREE from 1796 ppm in the apatite from the wall zone to 0 ppm in the core zone; and Y from 1503 ppm in the apatite from the wall zone to 0 ppm in the core zone); which could be due to early crystallization of REE-bearing phosphates such as monazite and xenotime. Strontium shows a more complex trend, with an initial depletion in apatite from the wall zone (52 ppm) to the intermediate zone (3 ppm) and a pronounced increase from the core margin (23–87 ppm) up to the core zone and pockets (up to 2.87 wt%). This increase of Sr at the latest fractionation stages of the pegmatite is interpreted to be associated with a late, incompatible character of this element in highly fractionated melts, related to the composition of feldspars from the core margin (mainly pure albite). The lack of Ca in feldspars would decrease affinity for Sr incorporation into their structure and, consequently, Sr would go preferentially to apatite in the core zone pods and, more markedly, in the pockets. Apatite also records changes in the redox conditions during crystallization, with the highest f O 2 at the end of the crystallization, mainly reflected in the Eu and Ce anomalies. The chemistry of apatite also reflects the evolution of the pegmatitic melt during crystallization regarding the fluids saturation and pockets generation. Accordingly, at least two exsolution events took place during the Berry-Havey crystallization history: (1) at the beginning of the core zone crystallization, giving rise to the Li-poor pockets, and (2) after the crystallization of the Li-rich pods of the core zone, resulting in the Li-rich pockets. The apatite-rich seams may have crystallized between these two exsolution events or later, at a subsolidus stage, after a Na-autometasomatism episode. This study shows how a detailed petrographic and chemical characterization of apatite associated with different units of a highly fractionated, internally zoned pegmatite may help understand the crystallization history of pegmatitic melts. It is also evidenced that during the internal evolution of pegmatites, apatite chemistry records variations in the f O 2 , elemental fractionation, interaction with competing mineral phases, fluids activity and exsolution events. In addition, it is shown how apatite chemistry may be useful as an exploration tool for pegmatites.

A set of 23 vesbine-bearing samples from Vesuvius volcano (Italy), preserved in the collection of the Royal Mineralogical Museum of Naples, University Federico II (RMMN), have been investigated to identify the mineral assemblages and their mode of formation. In the late 19th century, fumarole-related yellow patinas coating some historical lavas from Vesuvius were believed by Scacchi to contain a new element, vesbium, similar to vanadium in a mineral he called vesbine. Subsequent studies rejected vesbium and showed that vesbine was a poorly defined mixture of copper vanadates and halides. The vesbine samples studied here consist of yellowish to yellow-green-blue encrustations on Vesuvius lavas and have been analyzed by combined optical microscopy, SEM-EDS, XRPD, FTIR, and TEM-HRTEM-EDS. Results reveal complex mineral associations, including vanadates, halides, carbonates, oxides, silicates, tungstates/molybdates, and sulfates. The vanadates correspond to mottramite, volborthite, and vanadinite; subordinate amounts of descloizite were detected by XRPD and FTIR investigations. Several additional non-essential elements have been detected in the vanadates, including Mn, Zn, and As. The occurrence of wulfenite- and stolzite-rich phases indicates the presence of Mo and W, along with Pb, in the mineralizing fluids. Mn-rich phases, commonly in mixtures with silicates and vanadates, were also observed. These minerals are formed by a combination of different processes, including rock-fluid interactions, gas-water interactions, and alteration/oxidation of primary fumarolic minerals. Temperatures for the depositions of the vanadates-bearing assemblages are interpreted to be in the range of 100 to 400 °C.

We systematically investigated H 2 O solubility in majorite as a function of temperature from 1670–2270 K under a pressure of 20 GPa using multi-anvil techniques. The H 2 O solubility in majorite decreases with increasing temperature. In addition, the H 2 O content is relatively independent of the concentrations of Al 2 O 3 and SiO 2 in majorite. Majorite can store more H 2 O than bridgmanite in the lower mantle. Therefore, when a slab sinks into the lower mantle, hydrous melt could be produced not only by the phase transformation from ringwoodite to bridgmanite + ferropericlase near 660 km depth but also by the majorite to bridgmanite transformation over a wide range of depths from 660 km up to ~800 km, at which majorite dissolves completely in bridgmanite.

Ilmenite (Fe 2+ TiO 3 ) and geikielite (MgTiO 3 ) are important terrestrial minerals relevant to the geology of the Earth, the Moon, Mars, and meteorite samples. Raman spectroscopy is a powerful technique that allows for mineral cation determination for the ilmenite–geikielite solid solution. We report on a suite of nine samples within the ilmenite–geikielite solid solution and provide context for their quantitative interpretation. We compare a univariate Raman peak position model for predicting ilmenite composition with a multivariate machine learning model. The univariate model is currently recommended, though the multivariate model may become superior if the data set size is increased. This study lays the groundwork for quantifying Fe (ilmenite) and Mg (geikielite) within oxide minerals using a cheap, portable, and efficient technology like Raman spectroscopy.