The rare-earth elements, comprising the lanthanides (La-Lu) plus scandium and yttrium, exhibit unique structural chemistry characterized by large ionic radii, high coordination numbers, and distinctive electronic configurations. The systematic decrease in ionic radius across the lanthanide series, known as lanthanide contraction, provides an opportunity to study structure-property relationships in crystal chemistry. In this study, the structural parameters across major rare-earth compound families are examined, including rare-earth sesquioxides, phosphates, garnets and perovskites focusing on how geometric constraints and ionic size effects dictate crystal structure preferences. The profound impact of lanthanide contraction on structural chemistry is demonstrated. Key findings include predictable trends in bond lengths, coordination numbers, and polymorphic transitions that correlate directly with ionic radius changes from La³⁺ to Lu³⁺. Distortion parameters increase systematically with lanthanide contraction, affecting optical and magnetic properties. These systematic trends demonstrate the power of comparative structural analysis in understanding and predicting rare-earth compound behavior. These quantitative structure-property relationships provide valuable tools for materials design and property optimization.

The famous "St. Mark's Lion" now located in the Piazzetta of Venice is probably the greatest enigma in the relatively sparse repertoire of great ancient bronzes. Representing the Venetian Winged Lion, a powerful symbol of statehood, the sculpture was installed during a time of political uncertainty in medieval Mediterranean Europe, yet its features do not reflect local artistic conventions. A critical re-assessment of the state of art, together with additional stylistic comparisons and historical considerations indicate in the ancient Chinese art styles and iconography used are the roots of the unusual facial features of the 'Lion'. The authors argue that stylistic parallels are found in Tang Dynasty China (AD 618–907).

Lead isotopes analyses (LIA) of the metal in the earliest cast parts of the statue strongly support the hypothesis of a Chinese origin, indicating that the figure was cast with copper isotopically consistent with ores from the Lower Yangtze River basin and thus creating a very early link across the Eurasian silk road [1]. The new involved narrative, therefore, surprisingly tells us about the possible import from China to Venice of an enormous statue of a winged hybrid monster, in the framework of the twelfth century official replacement of the Byzantine urban cult of St. Theodore with that of St. Mark [2][3].

Authigenic pyrite is prevalent in the sedimentary deposits of Brunei Darussalam, occurring in well-defined morphologies such as cubes, pyritohedra, octahedra, and framboidal textures. These sulphide minerals are commonly associated with clay-rich matrices and lignitic horizons, indicative of anoxic depositional environments enriched in organic matter that facilitate pyrite formation. Upon exposure, pyrite undergoes oxidation, often accelerated by microbial activity, producing native sulphur and gypsum. Pyrite oxidation releases Fe²⁺ which is oxidised to Fe³⁺ subsequently forming Fe-oxides such as goethite, hematite and limonite. These phases contribute to the reddish pigmentation of soils and act as cementing agents in arenitic sands, forming ferricrusts. The geochemical alteration of pyrite significantly lowers the pH of surrounding soils, resulting in acidic conditions that pose serious challenges to agriculture and aquatic ecosystems due to the discharge of acidified waters. This study elucidates the mineralogical evolution and environmental consequences of pyrite-bearing sediments in Brunei, underscoring the need for targeted mitigation strategies in acid sulphate soil landscapes.

Fly ash, a by-product of coal combustion in industrial energy production, is generated in substantial quantities at industries in Brunei Darussalam, with an estimated daily output of approximately 9 tonnes. This study presents a detailed mineralogical and physicochemical characterisation of fly ash samples collected from the facilities. X-ray diffraction analysis reveals quartz as the dominant mineral phase, with subordinate zeolites present. Thermogravimetric analysis confirms the thermal stability of the material, supporting its potential for reuse in construction applications. Physicochemical properties of the fly ash samples reveal moisture contents ranging from 2 to 60 wt%, pH values between 7.5 and 8.9, electrical conductivity (EC) from 450 to 3670 µS/cm, and redox potential (Eh) ranging from 163 to 250 mV, indicating moderately oxidising conditions. The material is classified as Class F under ASTM standards and Type F under CSA guidelines. BET surface area measurements indicate moderate porosity, which enhances its reactivity and supports its potential use in cementitious systems and as a sorbent material. These characteristics make the fly ash suitable for incorporation into bricks, concrete, and other geotechnical applications, contributing to sustainable construction practices. Moreover, due to its buffering capacity and mineral composition, the fly ash may also serve as a soil conditioner, potentially aiding in pH regulation and improving soil structure in poor agricultural soils. Trace element analysis indicates relative enrichment of certain elements, which may pose environmental concerns if not properly managed. While current data suggest manageable levels, further geochemical and leaching studies are required to fully assess long-term environmental risks and inform safe reuse strategies. This research highlights the importance of developing integrated waste valorisation frameworks and regulatory support to promote circular economy principles and sustainable industrial development in Brunei Darussalam.

Color is a defining characteristic of gem diamonds, influenced significantly by the presence of H3 (2N+V) and H4 (4N+2V) color centers. These defects impact both absorption and fluorescence, contributing to the attractive fancy yellow-green hues observed in some diamonds. H3 and H4 centers can form naturally in the Earth’s crust through long-term geological processes involving irradiation and annealing. However, they can also be artificially produced by exposing diamonds to high-energy electron beams followed by laboratory annealing. Distinguishing between naturally and artificially formed color centers is critically important for the gemological industry.

In this study, we report the occurrence of H3 and H4 centers in diamonds from a unique alluvial deposit in Africa. These diamonds, averaging approximately 3 carats in size, were found in quartz pebble and cobble conglomerates overlying the basal sediments of the Umkondo Group (1.11 Ga). The surfaces of the diamonds exhibited extensive green and brown radiation stains, indicating strong natural irradiation and annealing. As a result, significant concentrations of H3 and H4 centers were introduced, and some diamonds with appropriate nitrogen levels displayed fancy yellow-green coloration. This marks the first confirmed discovery of a diamond source consistently producing such naturally colored diamonds.

To compare with artificial processes, 17 colorless diamonds containing suitable nitrogen concentrations were irradiated using a 2 MeV electron beam and subsequently annealed at high temperatures. These treated diamonds also developed fancy yellow-green colors due to the formation of H3 and H4 centers.

Both natural and treated diamonds were extensively analyzed using a range of spectroscopic techniques, including infrared and UV-Visible absorption spectroscopy, and photoluminescence spectroscopy at liquid nitrogen temperatures using laser excitations at 830 nm, 633 nm, 532 nm, 514 nm, and 457 nm. The study identified distinct spectroscopic differences between natural and artificially treated diamonds, enabling reliable separation in gemological testing. While the formation mechanisms of H3 and H4 centers are fundamentally similar, differences in irradiation intensity, exposure duration, and annealing conditions—particularly the formation of additional lattice defects such as interstitials—play a key role in distinguishing the two origins.

Wide changes in reservoir quality and abundant heterogeneity in reservoirs lead to the inherent difficulty of production and enhanced oil recovery from these reservoirs. This difficulty is the result of the influence of related parameters, including facies and sedimentary environment, diagenesis processes and tectonic transformation and basin morphology. The reservoir quality of a formation depends on diagenetic processes in addition to initial conditions of deposition. In fact, diagenesis is an important controlling factor in many hydrocarbon reservoirs. Many changes in the distribution of facies during diagenesis cause heterogeneity in oil and gas reservoirs. Investigation of diagenesis processes shows that the most important diagenesis processes affecting a geological formation are several generations of fractures and burial pressure dissolution and cementation, dolomitization and micriteization, compaction and compression (mechanical and chemical). Diagenesis, the process of transforming sediment into sedimentary rock, involves significant geochemical changes that are studied using geochemical methods. In this paper, effects of diagenesis processes on reservoir quality of a geological formation will be discussed. 

Interest in materials exhibiting ionic conduction or mixed ionic-electronic conduction has increased during the last years owing to their great importance for energy and environmental applications, such as solid oxide fuel cells for converting chemical to electrical energy, solid oxide electrolyser cells for high-temperature electrolysis of water, and oxygen permeation membranes for chemical reactions. In memristic devices transport of ions due to an external electric bias modulates the electronic conductivity of the devices and renders possible multilevel resistive switching being the basis for neuromorphic computing. Perovskite oxides are regarded as key materials for the above energy applications and for memristic devices as well. 

We will discuss our ab initio studies of proton and oxygen ion transport in doped BaZrO₃ based on density-functional theory (DFT) and Kinetic Monte Carlo (KMC) simulations [1,2]. In SrTiO₃ we found memristic behaviour triggered by transport of oxygen ions and resulting in filamentary switching or bulk switching depending on the experimental conditions [3,4]. Finally, we will discuss or recent findings on variable-range hopping of electrons in amorphous gallium oxide that also shows bulk resistive switching [5]. 

Minerals, the naturally occurring crystalline chemical solids, comprising planet Earth underpin many societal advances. From the beginnings of humankind, Earth’s minerals have been essential for artistic expression, scientific and technological advances, and for the well-being of society. Prior to written language, paintings made of mineral pigments decorated caves. Personal adornment exploited a wide variety of mineral gemstones that continues today. Early Homo sapiens separated different minerals based on their physical properties, advancing uses for food gathering and protection. Utilization of these minerals defines the Ages of Humankind: Stone, Bronze, Iron and Technological ages [1]. Ben Franklin used the pyroelectric and piezoelectric properties of the mineral tourmaline for supporting his theory of electricity.  Diamond, nature’s hardest substance, is not only a highly prized gemstone but has a myriad of applications such as a substrate for electronics due to the exceptional 3D heat transporting properties. Two areas underscore the criticality of minerals to the science and technological needs leading to a more sustainable future.

The chemical constituents extracted from minerals power advances in the clean energy transition. Predictions indicate that total mineral demand from clean energy technologies will double to quadruple depending on the scenario [2]. Battery storage materials (lithium, graphite, cobalt, nickel, manganese) account for nearly half of the mineral requirements. Some minerals find application essentially as the occur, e.g. graphite and copper, whereas others are refined to extract their constituents; the critical elements needed across the spectrum of existing and proposed new technologies. As examples, rare earth elements (REEs), with unique properties essential to hybrid and electric cars, high-strength magnets for wind turbines and as components in solar photovoltaic cells, are housed in unusual minerals (RE phosphates) or adsorbed onto their surfaces (e.g. clays). Uncommon geochemical environments are required to concentrate these trace elements, with an average of ~169 𝜇g/g in the continental crust [3], into deposits that can be mined profitably. A 50% increase in demand is projected in 10 years [2]. REE deposits are not uniformly distributed across Earth’s surface, creating countries with few resources and those with abundant resources. Lithium, a critical element for batteries, is extracted largely from minerals and must similarly be concentrated into an extractable ore. Lithium is rare in the bulk silicate earth (~1.39 𝜇g/g on average) but concentrated in the upper continental crust from ~21 𝜇g/g to 7,000 𝜇g/g [4]. Of the 124 known Li minerals, about 73% are silicates of which about four occur in sufficient quantities to be mined. Nearly 50% of the world’s lithium derives from minerals in one country, Australia [4]. While many countries have reserves, also in brines, over 40 times the current demand will be needed by 2040 in the scenario of rechargeable batteries [2]. From aluminum to zinc, the elements extracted from minerals form the basis for advanced materials. The global energy transition has far-reaching consequences for mineral demand over the next few decades.

Geothermal energy is a sustainable and clean source of power that harnesses heat from within the Earth, typically involving circulation of hot fluids. However, understanding the long-term evolution of high-temperature geothermal systems remains challenging. Two primary approaches are used to investigate these systems: (1) numerical modelling of geothermal processes, and (2) analyzing minerals that form within the system. Geothermal (hydrothermal) systems are modelled as a complex interplay of non-linear thermal, mechanical, and chemical feedback among fluids and minerals [5]. Certain minerals can record thermal evolution by acting as natural thermometers. One such mineral is tourmaline, a chemically complex borosilicate that incorporates the fluid-mobile element boron. Tourmaline has an exceptional ability to capture geochemical and thermal conditions during its growth. Its crystallographic sectors partition chemical elements in a way that allows sector zoning to function as a mineral thermometer [6]. When geochemical conditions change rapidly, oscillatory zoning may develop, overlaying the intersector partitioning to create a detailed record of the system's thermal history. This approach is demonstrated by sector-, and oscillatory-zoned tourmalines from the Siglo XX hydrothermal system in Bolivia. Chemical analysis by the electron microprobe indicates that temperatures during tourmaline formation occurred at about 380°C, gradually dropped to around 300°C, and later rose again to approximately 470°C when growth ceased. Such findings showcase the power of mineral-based methods to reconstruct the thermal evolution of geothermal systems and complement traditional modelling techniques for understanding the system’s lifetime. As the world strives to a sustainable future, minerals play an essential role for the new, carbon-free, advanced technologies.

Chromitites uniquely catalyse low‑temperature methane formation [1], motivating data‑driven exploration of naturally occurring catalysts for CO₂ methanation aligned with sustainable energy goals [2]. Using 12 Greek chromitite samples with quantified methane, petrographic point counting and grain‑size distributions were encoded via percentile ranks and modeled with a super‑ensemble that stacks Multinomial Naive Bayes with XGBoost, guided by automated model search and manual tuning. The selected classifier achieved 75% training and 71% test accuracy, outperforming alternative algorithms evaluated on these data. Model interpretability using SHAP [3] and partial dependence plots identified several key predictors of high methane levels. Large olivine crystals within chromitites emerged as the strongest positive predictor. Medium-sized veins showed a positive association, while large veins had adverse effects. Large spinel crystals acted as a secondary, though weaker, indicator. The workflow converts petrographic observations—often visible at hand‑specimen scale—into practical field criteria for targeting chromitites that host mineral catalysts, thereby reducing reliance on synthetic catalysts and mitigating pressure on noble and critical metal supply chains. This first application of machine learning to field exploration of mineral catalysts demonstrates how tree‑based, interpretable ensembles can capture complex relationships in multivariate petrographic data and enable precision exploration for carbon‑neutral energy materials.

Earth's systems, in manifold ways, feature characteristic rhythmic patterns such as banded formations, layered and folded structures, diapirs or cockade ores that can range from just microns, and even sub-microns, up to kilometers in scale. This subject has been examined from a thermochemical/ thermomechanical perspective since time immemorial. 

Likewise, the physical perspective was for a long time limited to characterizing continuous changes in closed systems. The concept of self-organization (I. Prigogine, 1977), however, makes it possible to describe discontinuities as spontaneous sequential structure/texture formation. For this reason, the earlier approach in closed systems with given boundary conditions of existing "ideal gases" is abandoned, and instead, open systems with distributed components and properties (W. Ebeling, 1976) as well as available free energy are introduced. To enable spontaneous structure/texture formation, the open systems should be far from thermodynamic equilibrium.

Looking at closed systems, changes inevitably cause an increase in complexity and disorder (increase in entropy). In contrast, the concept of self-organization in open systems lays the foundation for changes paired with simultaneously increasing order and complexity by means of entropy export and energy dissipation in which phase transitions play an essential role. Precipitate patterns facilitated by solute reactions have been discussed in detail since the 1980s (P. Ortoleva, 1982). Another characteristic of open systems, the scale invariance, is formulated by H. Haken 1978 with his synergetics concept.

As the Earth´s system in general is considered as an open system comprising geochemical processes and geomaterials of all scales that changes because of the supply and withdrawal of energy, ordered structures and patterns are typical features in Earth´s universe of processes and remarkable rocks.

In this talk, radiolarite, malachite, reef limestone and banded iron-manganese deposits will be addressed as illustrating examples. Using the example of a recent early diagenetic mineral formation, the findings of experimental, theoretical, and numerical analyses will be looked at in detail unveiling access to desired minerals and valuable mineral resources. Finally, generalized results will be considered for future investigation.

 Staurolite-rich metapelites near Rangeley, Maine, USA, have three basic types of crystal size distributions that provide insight into the mechanisms that control nucleation and growth during metamorphism.  An early Devonian period of regional heating (M2 metamorphism) produced more or less equant staurolite about ½ cm in diameter that are evenly distributed throughout individual compositional layers in a hand specimen. These M2 staurolites were later affected by hydrothermal systems and thermal gradients related to intrusion of late Devonian plutons (M3 metamorphism).  Rocks with M2 staurolite located far from the M3 intrusions were rehydrated at M3 garnet and biotite grade conditions; rocks with M2 staurolite at an intermediate distance from the M3 intrusions were unchanged because M3 Tmax  was at staurolite grade conditions; and rocks close to the M3 intrusions  experienced prograde metamorphism at sillimanite grade conditions[1].  Late M3 (M3+) staurolite growth in the early M3 garnet zone is produced by heating due to small local intrusions or advective flow.  Heating due to late M3 intrusions produce many small (~0.1 mm) staurolites concentrated in early M3 chlorite + muscovite pseudomorphs after M2 staurolites; heating due to advective fluid flow produces large (~1cm) staurolites distributed randomly throughout a hand specimen irrespective to the location of early M3 retrograde pseudomorphs after staurolite. These different patterns are produced by differences in the scale of local equilibrium, which influenced staurolite nucleation and growth as the late M3 staurolite isograd was overstepped in the M3 garnet zone.  Rocks near late M3 intrusions, where the heating rate was rapid, but with little advective flow, had small domains of equilibrium.  This produced clusters of small crystals where nucleation was strongly influenced by local compositional heterogeneity due to chlorite + muscovite pseudomorphs after M2 staurolite.   Conversely, rocks where heat was advectively transported along late M3 fluid transport paths have large domains of equilibrium due to the advective transport, so fewer staurolites nucleated before significant growth began and nucleation patterns were unaffected by the local compositional heterogeneity due to the early M3 chlorite + muscovite pseudomorphs after M2 staurolite.  

Planets that orbit stars other than our sun are called exoplanets. Over 6,000 exoplanets have been confirmed in our galaxy. Hot Jupiters are a type of exoplanet that orbit very close to their star and are tidally locked, with a permanent daytime and nighttime side. Brown Dwarfs are a type of planet that are failed stars. Being the hottest exoplanets, these emit the most radiation and thus are a prime target for the James Webb Space Telescope. Silicates are a ubiquitous feature of aerosols on hot giant exoplanets ¹. WASP 17-b is a hot Jupiter with an orbital period of 3.7 days whose atmosphere was recently observed by James Webb Space Telescope to be dominated by quartz (SiO₂) nanocrystals, although magnesium-rich silicates were expected to be seen ². In the brown dwarf VHS 1256-1257b, the best fit models for spectroscopic observations were clouds of enstatite (MgSiO₃), forsterite (Mg₂SiO₄), and quartz (SiO₂) ³. Despite key silicate features in spectroscopy, it is not possible to determine complete atmospheric composition and cloud formation by astronomical observations alone, and particle formation in atmospheres must be modeled. A major factor in modeling atmospheres is condensation and nucleation, which is exponentially dependent on the species’ surface energy, with higher surface energies drastically hindering nucleation rates. Although the significance of surface energy measurements is evident, surface energies of several key species in hot giant exoplanets are not yet constrained by experiment. In this work, surface energies of likely exoplanet atmosphere condensates, including zinc sulfide (ZnS), crystalline and amorphous enstatite (MgSiO₃) ^4,5 were measured using oxide melt solution calorimetry  of appropriate nanoparticles. These are then input into a nucleation code that gives nucleation rates for these species. The surface energy of crystalline SiO₂ is much lower than that of the crystalline magnesium-rich silicates ^4,6, supporting the observation of silica in the atmosphere of WASP-17b, while the surface energies measured in our lab of amorphous enstatite and amorphous forsterite are much lower than their crystalline counterparts and closer to the surface energy of quartz. This suggests that the initial nucleation of MgSiO₃ in VHS 1256-1257b forms the amorphous phase. This research is of significant importance to the interpretation of observations of exoplanets. In particular, our research provides laboratory data of high relevance to a broad range of exoplanet atmospheres.

Mg-Al spinel (MgAl₂O₄, MAS) is a common rock-forming mineral widely distributed in the upper mantle, crust, and extraterrestrial bodies [1]. The order-disorder transition (ODT) in spinel is a critical physical characteristic that significantly affects its properties and applications as a geothermometer for probing the thermal history of Earth and extraterrestrial bodies [2]. Although activation energy—a key thermodynamic parameter of ODT—is reported to be influenced by Cr content [3,4], the relationship between these two factors remains unclear. 

In this work, six natural Mg-Al spinel samples with varying Cr contents (419 – 6918 ppma) were studied. Each sample was cut into eight slices and heated to seven different temperatures (550–850 ^◦C) by a muffle furnace (model YFX9/16Q-YC), creating a stepwise increase in the degree of disorder. Photoluminescence (PL) spectra were subsequently collected at liquid nitrogen temperature (JASCO NRS7500 Raman spectrometer). 

The PL spectrum emitted by Cr in the samples consists of zero-phonon lines (ZPL) and phonon sidebands, with a spectral range between 13800 and 14640 cm^-1. The ZPL, located between 14500 and 14640 cm^-1, comprises R peaks (R₁ and R₂) and N peaks (n₅, N₂, n₃, and N₁). R₁ and R₂ are emitted by the Cr³⁺ ions around which the cation arrangement is ordered, while the disordered arrangement emits the N peaks. The intensity of the N peaks in the zero-phonon line range and the N₄ peak increased with increasing Cr content. 

By integrating parameters extracted from these spectra into a thermodynamic model, which we established in previous work based on the Arrhenius relationship [5], we calculated the ODT activation energies, which decreased from 335 to 163 kJ/mol as the Cr content increased. A quantitative relationship between activation energy and Cr content was established: Ea = − 0.03[Cr] + 356.28. As a result, we clarify the negative correlation between ODT activation energy and Cr content in Mg-Al spinel, which may be attributed to local structural distortion caused by the presence of Cr-pairs. 

This study provides a method to correct the influence of Cr content on ODT thermodynamic models, thereby enhancing the viability of spinel as geothermometers and deepening the scientific understanding of how elemental composition affects the thermal stability of spinel [6]. 

Tourmaline is the most significant borosilicate mineral in the Earth's crust due to its exceptional stability and its capacity to incorporate a wide range of elements from its surrounding environment. The general chemical formula of tourmaline is X Y₃ Z₆ T₆ (BO₃)₃ O₁₈ (V)₃ (W), where the most common substituents are X = Na, Ca, K or [  ] (X-site vacancy); Y = Al, Li, Fe²⁺, Mg, Mn²⁺, Fe³⁺, V³⁺, Cr³⁺, Ti⁴⁺; Z = Al, Mg, Cr³⁺, V³⁺, Fe²⁺ and Fe³⁺; T = Si, Al, B; V = OH^1-, O^2- and W = F^1-, O^2-, OH^1- [1]. As a result, it serves as a robust recorder of the geochemical conditions under which it forms. Structurally, tourmaline is an asymmetric cyclosilicate that exhibits both pyroelectric and piezoelectric properties. It occurs in a diverse range of geological and geochemical settings. The temperature and pressure stability range of tourmaline extends from below ~150°C to over 900°C and from ~1 MPa to over 4 GPa, encompassing nearly the entire range of conditions found in the Earth's crust [2]. In addition to its thermal and baric stability, it has extreme mechanical durability and is an important detrital heavy mineral in clastic sedimentary environments for provenance. Once buried and heated in a metamorphic setting, this sedimentary tourmaline grain commonly serves as a nucleus for further tourmaline. As it develops in the metamorphic environment, the new metamorphic tourmaline changes its composition in response to the chemical environment. Further, once it is crystallized, it holds that compositions without homogenizing at elevated temperatures i.e. it is an exceptional record of the evolving chemical environment during metamorphism.

Two case studies showcase how tourmaline's chemistry and textures can be used to trace the geochemical and mineralogical evolution of metamorphic rocks, using imaging and micro-analytical data from the LSU Electron Microprobe. Case study 1 – Detrital tourmaline grains and their associated tourmaline overgrowths in 380 Ma low-grade clastic metasedimentary rocks from Maine, USA [3]. The chlorite-zone metasedimentary rocks contain tourmaline with three well-defined zones: a detrital core with a metamorphic overgrowth consisting of an inner mantle and an outer rim of an overgrowth.  The detrital cores were derived from a variety of source rocks, including low-grade siltstone, Al-poor metasandstone, medium-grade aluminous metapelite, low-Li granite, Li-rich granite, and calcareous metasediment. This diversity suggests a heterogeneous sedimentary input and complex provenance history. Metamorphic overgrowths reflect diagenetic to low-grade metamorphic processes. A diagnostic chemical trend is Mg replaces Fe²⁺ in the metamorphic overgrowths at a 1:1 ratio reflecting changes in the metamorphic environment with progressive metamorphism. Case study 2 – Tourmaline from a 550-500 Ma metamorphosed evaporite from Namibia [4]. Tourmaline from meta-evaporitic tourmalinites of central Namibia share compositional similarities with tourmalines from other meta-evaporite localities worldwide, suggesting a common geochemical process. The meta-evaporitic tourmalines are generally sodic, magnesian, moderately-to-highly depleted in Al, and enriched in Fe³⁺ with a diagnostic substitution of Fe³⁺ replacing Al at a 1:1 ratio. These latter tourmaline compositions reflect metasomatic processes that produced these unusual bulk compositions found in evaporite deposits and/or the influx of a reactive fluid that eliminated any earlier chemical signatures of meta-evaporitic fluids or protoliths. This chemical feature is attributed to the influence of oxidizing, highly saline, boron-bearing fluids that are associated with these meta-evaporite lithologies. These studies demonstrate the unparalleled geological history embedded in a crystalline solid.