Abstract Modraite, ideally Ca19Fe2+Al4(Al7Fe2+)(SiO4)10(Si2O7)4O(OH)9, is a new member of the vesuvianite group. It was found at Modra, Harmónia skarn rock in the Malé Karpaty Mountains, Pezinok District, Slovakia. Modraite formed as a high-temperature and low-pressure metamorphic mineral on the contact zone between Devonian limestones and Carboniferous granitic rocks, in association with diopside-hedenbergite, rarely grossular, calcite, titanite, and clinozoisite-epidote. The new mineral forms dark brown microscopically transparent euhedral to subhedral prismatic crystals or radiating aggregates (up to 5 cm long) in diopside-hedenbergite groundmass. Modraite crystals are characterized by dominant {100} and minor {110} prism faces; the mineral is brittle, has an irregular (uneven) fracture without cleavage or parting. The Mohs’ hardness is 6−7. The measured and calculated densities are 3.35(2) and 3.42 g/cm3, respectively. The new mineral is microscopically transparent to translucent, optically uniaxial, negative, ω = 1.7221(2), ε = 1.7151(3). The mean chemical composition of modraite (wt%, electron microprobe, REE and Li by LA-ICP-MS, Fe2O3 and FeO by Mössbauer spectroscopy, H2O calculated from stoichiometry) is: SiO2 36.42, TiO2 1.79, Al2O3 16.37, V2O3 0.03, Cr2O3 0.03, La2O3 0.03, Ce2O3 0.08, Pr2O3 0.01, Nd2O3 0.04, Sm2O3 0.01, Gd2O3 0.01, Fe2O3 1.32, FeO 3.65, MnO 0.23, ZnO 0.05, MgO 0.87, CaO 34.92, BaO 0.26, Li2O 0.03, Na2O 0.09, H2O 1.80, F 1.49, Cl 0.16, O=F -0.63, O=Cl -0.04, total 99.02. The empirical formula based on 50 cations (excluding H) per formula unit is: X1–X4(Ca18.60Na0.09Ba0.05Ce0.02La0.01Nd0.01)Σ18.78Y1(Fe2+0.81Fe3+0.13Al0.09)Σ1.03Y2Al4Y3(Al5.50Fe2+0.71Ti4+0.67Mg0.65Fe3+0.36Mn2+0.10Li+0.06Zn2+0.02 V3+0.01Cr3+0.01)Σ8.09T1(□4) T2□ (Z1–Z2Si1.01O4)10 (Z3Si2O7)4O10–O11(OH5.97F2.34O1.55Cl0.14)Σ10.00. Mössbauer spectroscopy indicates a dominant proportion of Fe2+ (76 %) over Fe3+ (24 %), with the dominancy of Fe2+ over Fe3+ at both the Y1 and Y3 sites. The crystal structure was refined to R1 = 0.0215 for 3970 unique reflections. The mineral is tetragonal, space group P4/nnc, single-crystal X-ray diffraction data of a modraite are: a = 15.559(2) Å, c = 11.804(2) Å, V = 2857.4(9) Å3, Z = 2. The seven strongest lines of the powder X-ray diffraction pattern are [d(Å)−I(%)−hkl]: 3.235−19−402, 2.949−29−004, 2.749−100−432, 2.593−59−522, 2.458−37−620, 1.625−16−526, 1.621−30−922. Modraite is the Y1Fe2+-dominant member, ideally with 7 Al3+ and 1 Fe2+ cations at the Y3 site, and a strong O10-H10…O10 hydrogen bond. Modraite is named after the type locality, Modra, western Slovakia.

The bond-valence topological graph represents a segment of the structure that can be chosen based on the studied phenomena. In bond-valence topological graphs, atoms or structural sites are vertices, and bonds are edges of graphs. Bond-valence topological graphs are weighted; therefore, bond-valence or bond-length values are attached to every edge of the graph. The bond-valence topological model (BVTM) is the specific structural fragment represented as a bond-valence topological graph with attached values of bond valences or lengths. Bond-valence topological models can be used to create a bond-valence topological map of real mineral structures. This map is a composite of BVTM added together, which, as a result, should have identical properties to the real structure. Tourmaline from Forshammar, Sweden, with the composition of (X)(Na0.707Ca0.045K0.008) (Y,Z)(Al6.554Mg2.192Fe0.174Ti0.024 Mn0.004Zn0.002) (Si6O18)-Si-T ((BO3)-B-B)(3)(V,W)(OH3.464O0.507F0.028Cl0.001) was chosen for the bond-valence topological mapping because of the very low Fe and Mn content and relatively simple composition. The composition of tourmaline from Forshammar can be expressed as the sum of different ordered and disordered components: dravite, oxy-dravite, uvite, magnesio-foitite, magnesio-dutrowite, schorl, and schorl-dravite. Two factors were used for testing them: (1) long-range structural stability and (2) local bond-valence stability. Due to long-range stability, ordered dravite, uvite, and magnesio-dutrowite can be considered unstable because they are positioned clearly in the region of unstable structures. Considering local bond-valence stability, ordered components including dravite, schorl-dravite, schorl, oxy-dravite, and magnesio-dutrowite can be considered unstable due to the large difference in the bond-valence sum at various sites compared to their formal valence. The final topographic map of the bond valence showed that the examined tourmaline from Forshammar does not consist of ordered, but only of disordered components of these tourmaline end-members, except ordered magnesio-foitite.

Marsaalamite-(Y), ideally Y(MoO4)OH, is a new molybdate mineral discovered in the greisenised Um Safi F-rich granite located in the Marsa Alam District, Central Eastern Desert, Egypt. It typically occurs as inclusions in or intergrowths with F-rich zinnwaldite. It forms micaceous aggregates, with sizes varying from 0.1 to 1 mm. Marsaalamite-(Y) is non-magnetic, white in colour, and has an earthy lustre and white streak. It is brittle (3-4 Mohs) and has basal cleavages {010}. The calculated density is 4.90 g.cm-3 based on the empirical formula and unit-cell parameters refined from powder X-ray diffraction data. Marsaalamite-(Y) is associated with arsenopyrite, baryte, bastn & auml;site-(Ce), cassiterite, chernovite-(Y), columbite-(Fe), fluocerite-(Ce), fluorite, iron oxy-hydroxides, l & ouml;llingite, molybdenite, monazite-(Ce), pyrite, quartz, rutile, thorite, wolframite, wulfenite, xenotime-(Y) and several unidentified phases. The empirical formula is (Y0.67Er0.10Dy0.08Yb0.08Ho0.02Lu0.02Tm0.02Ca0.01)Sigma 1.00(Mo0.95S0.03As0.01P0.01)Sigma 1.00O4.00[(OH)0.88F0.11Cl0.01]Sigma 1.00; the ideal end-member formula is Y(MoO4)(OH). The presence of a hydroxyl group has been confirmed by Raman and infrared spectroscopy, and its concentration has been calculated from the stoichiometry. Marsaalamite-(Y) is the natural (OH)-dominant analogue of synthetic Y(MoO4)F. It is monoclinic, space group P21/c, with unit-cell parameters a = 5.1863(7) & Aring;, b = 12.3203(11) & Aring;, c = 6.6953(7) & Aring;, beta = 114.173(8)degrees, V = 390.30(8) & Aring;3, and Z = 4. Extreme fractionation of the parental halogen-rich, A-type granitic magma triggered the greisenisation of the granite. Marsaalamite-(Y) occurred simultaneously with or immediately after the crystallisation of F-rich zinnwaldite based on the textural relationship. Therefore, the crystallisation of marsaalamite-(Y) was most likely to have been controlled by fluid-induced processes rather than magmatic conditions. The new mineral has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2024-050) and named after the Marsa Alam District, Al-Bahr Al-Ahmer Governorate, Egypt.

Aluminium-rich tourmaline can contain significant amounts of Li. Until now, syntheses have not been successful in producing Li-rich tourmalines. Because it is still not clear how Li enters the Y site in tourmaline, possible short-range orders, including Li, are discussed using bond valence calculations. Structural arrangement graphs of the Y-site neighbourhood in the structure of elbaitic tourmalines were investigated to determine more information about their stability. Possible short-range ordering including Al and Li at the Y sites, with Na, Ca or square (vacancy) at the X site, with Si (and Al or B) at the T sites and either (OH) or F at the W site were investigated. Tourmaline with varying amounts of Na but no Ca can only contain <= 1 apfu (atoms per formula unit) Li-Y. This is consistent with the composition of synthetic tourmaline. Tourmaline with higher Li content (Li >1 apfu) can form when Ca is included. Such tourmaline requires fluorine because more Li results in O1 underbonding, whereas more Al at the Y site leads to O1 overbonding. Underbonding of O1 is preferable for F because OH at the O1 site usually has a bond valence sum (BVS) higher than 1.00 vu (valence units) due to hydrogen bonding of H to ring oxygen atoms. Therefore, liddicoatitic tourmaline is enriched in F and is usually F-dominant. If no fluorine is available in the starting material of a tourmaline synthesis, it is likely that significant proportions of cations such as B and Al will be incorporated into the tetrahedral site. Ultimately, however, only a smaller proportion of Li can be incorporated. Tourmalines with such tetrahedral cations, which also contain a significant Ca content, could theoretically also have significant Y-site vacancies. In order to synthesise Li-rich tourmalines, we would therefore recommend that the starting material also contains both Ca and F.

The article focuses on the archaeometric analysis of a medieval corundum ring from the Zvolen Castle in Central Slovakia, disclosing the valuable gemstone's origin and its use, cutting, and grinding. The ring, which is of high quality and rare in medieval jewels, was found at today's Pust & yacute; hrad (Deserted) Castle above the city of Zvolen. The prominent Hungarian High Medieval royal castle was built in the late 12th century and served as the administrative centre of the Zvolen County. The 18-karat golden ring, dating from circa 1300, holds a reddishpurple sapphire gemstone with an estimated weight of about 2.00 ct. The corundum was identified using standard gemological procedures, Raman spectroscopy, absorption spectroscopy, and microscopic inspection. It did not corroborate heat treatment indicators. An EDXRF examination for trace elements (Ti, V, Cr, Fe, Ga) helped to identify the sapphire's possible origin. The results indicate that Sri Lanka is the most likely place of origin. The ring's discovery highlights the importance of interdisciplinary collaboration in understanding medieval gemstone trade routes and usage. Such rings were far more than decorative items. The addition of engraved animals on the ring shoulders indicates the influence of medieval iconography and beastly imagery. The wearers used them as symbols of their wealth and societal status and as a spiritual safeguard.

Topaz is frequently subjected to heat treatment and irradiation to enhance colour, particularly to produce the market’s most preferred salmon pink and sky blue varieties. However, an insufficient description of these processes can lead to fraudulent practices. This experimental and forensic mineralogical and gemmological study investigates eighteen heat-treated topaz samples from Ouro Preto (OP) and Caraí (CA), Brazil, using electron microanalysis, LA-ICP-MS, Raman, and optical absorption spectroscopy before and after heat treatment at various temperatures. The most significant optical changes were observed at 300 °C when the CA sample lost its colour from sky blue to colourless, while OP samples retained their imperial orange colour up to 500 °C before transitioning to pink at 700 °C. Chemically, the CA samples are rich in F (> 1.8 apfu) with low trace element concentration (Fe ≤ 125 ppm, Ge ≤ 153 ppm), falling to the pegmatite and greisen field of topaz origin. The OP samples contain less F (1.4–1.5 apfu) but higher trace element contents (Cr up to 204 ppm, Ti up to 115 ppm, Fe, Mn, Ge < 64 ppm), consistent with a hydrothermal origin. Raman spectra show no significant inter-sample variation, but their luminescence spectra feature strong differences: Mn acts as the luminophore in CA samples, while Cr3+ centers dominate in OP samples. The optical absorption spectra reveal distinct thermal responses. The OP samples heated to temperatures ≥ 500 °C developed new absorption bands at 530–532 nm, consequently resulting in a visible pink colour. On the other hand, the CA spectra exhibit strong absorption in the NIR region; the unheated sample has a broad absorption band at 634 nm, responsible for the sky-blue colour of topaz. Heating ≥ 300 °C eliminates the transmission window in the blue to cyan regions, removing blue colouration. These thermal-optical signatures serve as indicators of heat treatment in topaz declared from these two localities. Moreover, the combination of spectroscopic methods, which we successfully applied in recognizing heat treatment on the studied samples, provides a systematic approach for identifying treatment in topaz and potentially other gemstones.

Xenotime-(Gd), ideally GdPO4, is a new mineral of the xenotime group. It was discovered at the Zimn & aacute; Voda REE-U-Au occurrence near Prakovce, Western Carpathians, Slovakia. It forms rare crystal domains (<= 20 mu m, usually <= 10 mu m in size) in Gd-rich xenotime-(Y) crystals (<= 100 mu m in size), in association with monazite-group minerals, uraninite, fluorapatite and uranyl arsenates-phosphates. The hydrothermal REE-U-Au mineralisation occurs in a quartz-muscovite vein, hosted in Palaeozoic phyllites near exocontact with Permian granites. The density is 5.26 g/cm(3), based on calculated average empirical formula and unit-cell parameters. The average chemical composition (n = 6) measured by electron microprobe is as follows (wt.%): P2O5 30.1, As2O5 0.5, SiO2 0.2, UO2 0.3, Y2O3 15.7, (La, Ce, Pr, Nd)(2)O-3 0.5, Sm2O3 5.7, Eu2O3 1.4, Gd2O3 29.2, Tb2O3 3.9, Dy2O3 10.4, Ho2O3 0.4, (Er, Tm, Yb, Lu)(2)O-3 2.1, (Ca, Fe, Pb, Mn, Ba)O 0.1, total 100.5. The corresponding empirical formula calculated on the basis of 4 oxygen atoms is: (Gd0.37Y0.32Dy0.13Sm0.08Tb0.05Eu0.02Er0.01Tm0.01Nd0.01 & mldr;)(Sigma 1.01)(P0.98As0.01Si0.01)O-4. The empirical formula of the Gd-richest composition is: (Gd0.38Y0.31Dy0.13Sm0.08Tb0.05Eu0.02Er0.01Nd0.01Ho0.01 & mldr;)(Sigma 1.01)(P0.98As0.01Si0.01)O-4. The ideal formula is GdPO4. The xenotime-type structure has been confirmed by micro-Raman spectroscopy and a Fast Fourier-Transform pattern using HRTEM. Xenotime-(Gd) is tetragonal, space group I4(1)/amd, a = 6.9589(5) & Aring;, c = 6.0518(6) & Aring;, V = 293.07(3) & Aring;(3) and Z = 4. The new mineral is named as an analogue of xenotime-(Y) and xenotime-(Yb) with Gd dominant among the REE. The middle REE enrichment of xenotime-(Gd) is shared with the associated monazite-(Gd) and Gd-rich hingganite-(Y). This exotic REE signature and precipitation of Gd-bearing minerals is a product of selective complexing and enrichment in MREE in low-temperature hydrothermal fluids by alteration of uraninite, brannerite and fluorapatite on a micro-scale. The existence of xenotime-(Gd) and monazite-(Gd) is the first naturally documented dimorphism among REE phosphates. In addition, xenotime-(Gd) is only the third approved Gd-dominant mineral, after lepersonnite-(Gd) and monazite-(Gd).

Beryllium mineralization was studied by EPMA and XRD techniques in the beryl-columbite pegmatite D6e from the Marsikov District, Bohemian Massif, Czech Republic. A detailed study of microtextures in BSE images revealed a complex formation of fine-grained secondary Be-silicates at the expense of primary beryl and earlier secondary Be-minerals in the following proximal and distal assemblages: (A) primary magmatic beryl; (B) proximal secondary beryl; (C) proximal bertrandite + K-feldspar and minor muscovite, chamosite, gismondine-Ca and quartz; (D1) proximal assemblages of milarite + gismondine-Ca and bavenite-bohseite + epidote; (D2) distal assemblages on brittle tectonic cracks including milarite, bavenite-bohseite, albite, K-feldspar, quartz and rare phenakite, and (D3) epidote, bavenite-bohseite, quartz, albite, K-feldspar and minor milarite. A formation of secondary Mg,Fe,V,Na-enriched beryl (B) is connected with a mixing of residual (pegmatite) and external Ca,Mg,Fe,V-enriched fluids from the host amphibole gneiss at T similar to 300-400 degrees C and P similar to 200-400 MPa. The assemblage (C) formed due to an income of K,Mg,Ca-enriched fluids (residual + external) at T similar to 150-300 degrees C. The subsequent proximal (D1) and distal (D2, D3) assemblages formed during an moderate to strong income of Ca-rich external fluids from the host rocks related to retrograde hydrothermal-metamorphic overprint manifested by the Alpine-type hydrothermal veins. A common presence of epidote in the assemblages with bavenite-bohseite suggests crystallization at T < similar to 200-300 degrees C. Detailed textural and paragenetic study of primary and secondary Be-minerals is a useful tool to recognize and study various processes proceeded during subsolidus evolution of granitic pegmatites.

We present a detailed study of thermally driven changes in Ca-dominant tourmaline using Electron Probe Microanalysis (EPMA), powder X-ray diffraction (PXRD), Raman and optical absorption spectroscopy (OAS). The KEN samples from Kenya (5 crystal fragments) can be classified as fluor-uvite, while TAN from Tanzania (5 fragments) is dominantly magnesio-lucchesiite. Tourmaline samples were thermally treated in air at 700, 800, 900, and 1000 degrees C. Both sets were green with different hues, TAN with a bluer hue than KEN. After heating, no significant visual changes were observed in TAN samples until breakdown at 1000 degrees C. In KEN, after heating at 700 degrees C, the yellowish tint disappeared. Raman spectroscopy showed no significant changes after heating. Raman luminescence spectra revealed the sharp intensive band located at 680-684 nm, accompanied by a broad band between 690 and 900 nm in all samples heated up to 900 degrees C. OAS spectra look similar, with two major bands in blue and yellow to red regions. In TAN, the bands shift with the increasing Cr/V from 608 to 604 nm. In KEN with low Cr/V, the band is located between 613-617 nm. After heating at 1000 degrees C, both samples broke down with different associations: cordierite/indialite and glass from magnesio-lucchesiite, and cordierite/indialite, mullite-like phase, spinel and glass from fluor-uvite. There was a difference in volume between the samples; both samples expanded in volume, but the KEN sample expanded more with larger pores likely resulting from a higher proportion of volatile phase in this sample.

Various chrysoberyl varieties (non-phenomenal chrysoberyl, alexandrite and cymophane) are gemstones of high demand; therefore, they are subjected to numerous substitutions by other materials and synthetic analogues. To address this issue, non-destructive methods for studying gemstones are highly sought after. Raman spectroscopy is one of the most suitable non-destructive methods for studying gemstones as it requires no sample preparation and does not leave any price-reducing signs on the gemstone surface. The research is focused on Raman spectroscopy application on chrysoberyl identification, differentiation between its varieties, inclusion analysis, and detection of synthetic analogues and imitations. The alexandrite variety can be identified by its broad luminescence band that ranges from 640 to 790 nm (15 625-12 658 cm(-1)). Synthetic alexandrite has sharper and more intensive bands on the luminescence spectrum, especially 690 and 696 nm (14 492-14 367 cm(-1)). Rutile inclusions can be distinguished by a broad band 580-640 cm(-1) in the Raman spectrum. Imitations of chrysoberyl represented by corundum and colour-changing spessartine was also identified. The orientation of faceted stones can also be determined by specific bands present in the Raman spectrum.

A hydrothermal quartz vein with REE-U-Au mineralization in the Zimna Voda (Gemeric Unit, Western Carpathians, Slovakia) is associated with contact metamorphism between Permian granites and host phyllites and metaquartzites. It contains unique REE minerals of the monazite and xenotime groups. Monazite-(Ce), monazite-(Nd), monazite-(Sm), and Gd-dominant monazite ["monazite-(Gd)"], along with xenotime-(Y) to Gd-dominant xenotime ["xenotime-(Gd)"] and Gd-rich hingganite-(Y) show heterogeneous compositions and reflect a strong fractionation trend toward the enrichment of MREE (Sm to Dy), particularly Gd. Here, the gadolinium abundance reported in "monazite-(Gd)" (=23.4 wt% Gd203) and Gd-rich xenotime-(Y) to "xenotime-(Gd)" (<28.7 wt% Gd203) and accompanied by Gd-rich hingganite-(Y) (<15.8 wt% Gd203), is among the highest Gd concentrations ever reported in natural minerals. The Gd-richest compositions show the following formulas: (Gd0.31Sm0.24 Nd0.15Ce0.10La0 .05Dy0.03Y0.03...)0.98P04 ["monazite-(Gd)"], (Gd0.36Y0.32Dy0.13Sm0.08Tb0.05...)0.98 (P0.96As0.04)1.0004 ["xenotime-(Gd)"] and (Y0.71Gd0.43Dy0.23Sm0.22Tb0.06Er0.04Nd0.06...Ca0.06)1.9 6 (o0.87Fe2+0.13)1.00(Be1.82B0.18)2.00(Si1.90As0.10)2.0008(OH1.7000.30)2.00 [hingganite-(Y)]. The MREE-rich monazites, xenotimes, and hingganite-(Y) precipitated in response to the alteration of primary uraninite, brannerite, and fluorapatite by low-temperature hydrothermal fluids of heterogeneous compositions on a microscale. These are responsible for the strong enrichment of individual MREE, especially Gd in the secondary minerals. This is accompanied by the advancing development of the W-type tetrad effect on REE through monazite species. The substantial incorporation of Gd into both REE-selective monazite and xenotime structures that are accompanied by LREE vs. HREE segregation indicates the possibility of differently sized REE3+ miscibility in REEPO4 solid solutions, as well as the stabilization of the Gd-rich orthophosphate structure by substitution of the remaining A-site cations with smaller HREE+Y in the xenotime-type, and/ or larger LREE in the monazite-type structure.

AbstractVanadium is the dominant trace element and chromophore in tanzanite, the most valued gemmological variety of zoisite. The structure of zoisite–tanzanite was obtained by structural refinement to assess the vanadium location in the zoisite structure. However, the small V content in tanzanite evidenced by electron microprobe and laser ablation inductively coupled plasma mass spectrometry limits the exact determination of the V position in the zoisite structure. Structural refinement revealed that the average bond length of the less distorted M1,2O6 octahedron is below 1.90 Å, and M3O6 has slightly longer bonds with an average of ca. 1.96 Å. The M1,2 site is slightly overbonded with a bond-valence sum (BVS) of 3.03 vu, whereas M3 is slightly underbonded (BVS = 2.78 vu). Optical absorption spectra revealed that most V is trivalent, but a small portion is probably in a four-valent state. Therefore, crystal field Superposition Model and Bond-Valence Model calculations were applied based on several necessary assumptions: (1) V occupies octahedral sites; and (2) it can occur in two oxidation states, V3+ or V4+. Crystal field Superposition Model calculations from the optical spectra indicated that V3+ prefers occupying the M1,2 site; the preference of V4+ from the present data was impossible to determine. Bond-Valence Model calculations revealed no unambiguous preference for V3+, although simple bond-length calculation suggests the preference of the M3 site. However, it is quite straightforward that the M1,2 site is better suitable for V4+. If the possible octahedral distortion is considered, the M1,2O6 octahedron is subject to a smaller change in distortion if occupied by V3+ than the M3O6 octahedron. Consequently, considering the results of both the crystal field Superposition Model and Bond-Valence Model calculations, we assume that both V3+ and V4+ prefer the M1,2 site.