The new mineral mazorite, ideally Ba3(PO4)2, a P-analogue of gurimite Ba3(VO4)2, was discovered in rankinite paralava hosted by the massive gehlenite-bearing pyrometamorphic rocks of the Hatrurim Complex in Israel. It has also recently been discovered in xenolith samples from the Bellerberg volcano in Germany. Holotype mazorite usually forms colourless plate-like crystals up to 70–100 μm in length but also occurs in small aggregates in association with other rare Ba-bearing minerals such as zadovite, celsian, hexacelsian, bennesherite, sanbornite, walstromite, fresnoite, gurimite, alforsite and barioferrite. The mineral is transparent, exhibits vitreous lustre and has a good cleavage on (001). Optically, mazorite is uniaxial (+), with ω = 1.760(3) and ɛ = 1.766(3) (λ = 589 nm). The empirical formula of the holotype mazorite calculated on 8O is (Ba2.69K0.22Na0.04Ca0.02Sr0.01)Σ2.98(P1.16V0.57S0.24Al0.04Si0.03)Σ2.04O8. Mazorite crystallises in space group R$\bar{3}$m, with unit-cell parameters a = 5.6617(5) Å, c = 21.1696(17) Å, V = 587.68(9) Å3 and Z = 3. Its crystal structure consists of BaO12, BaO10, and PO4 polyhedra, ordered along the c-axis in PO4–BaO10–BaO12–BaO10–PO4 columnar arrangement characteristic for palmierite-supergroup minerals. A tetrahedrally coordinated site is generally occupied by P5+ but can be partially substituted by V5+ and S6+. This substitution is shown in the Raman spectrum of mazorite, which reveals bands that can be assigned to the stretching and bending vibrations of (PO4)3–, (VO4)3– and (SO4)2– groups. The Raman spectra of mazorite from two localities (Hatrurim and Bellerberg) and spectra of minerals belonging to the mazorite Ba3(PO4)2 to gurimite Ba3(VO4)2 solid-solution series are presented. The gradual shift of the Raman bands, caused by cation substitutions, is well observed. The high V5+ → P5+ substitution is also observed for gurimite, for which the first X-ray structural data are also presented. Mazorite and other Ba-bearing minerals crystallised from a small portion of residual melt enriched in incompatible elements, such as Ba, V, P, U, S, Ti and Nb, at a temperature of ~1000°C.

Gismondine-Sr, recently discovered in the Hatrurim Complex in Israel, has been recognised in a xenolith sample from the Bellerberg volcano in Germany. The empirical crystal-chemical formula indicates elevated K content: (Sr1.74Ca1.05Ba0.09K1.56Na0.49)Σ4.93[Al7.98Si8.06O32]⋅9.62H2O. Additionally, Ba-rich gismondine and amicite have been found in the low-temperature mineral association of the pyrometamorphic rock from the Hatrurim Complex. The Raman spectra of the studied zeolites and the crystal structure of gismondine-Sr from the second occurrence are presented. A review of zeolites with GIS framework-type structure leads to the following conclusions: (1) garronite-Na and gobbinsite are equivalent and constitute a solid solution with garronite-Ca; (2) gismondine-Ca, -Sr, and amicite belong to one mineral series; (3) two zeolites series with different R-factors (defined as Si/(Si+Al+Fe)) can be distinguished within GIS topology: the garronite series (R > 0.6) including garronite-Ca and gobbinsite, with general formula (MyD0.5(x–y))[AlxSi(16–x)O32]⋅nH2O, where M and D refer to monovalent and divalent cations, respectively; and the gismondine series, including amicite, gismondine-Sr and gismondine-Ca, with R ≈ 0.5, and the general formula (MyD0.5(8–y))[Al8Si8O32]⋅nH2O. The Raman band between 475 cm–1 and 485 cm–1 is distinctive for the garronite series, whereas the band around 460 cm–1 is characteristic of the gismondine series. On the basis of these findings, a revision of GIS zeolites nomenclature is suggested.

The recently defined arctite supergroup contains nine mineral members defined as hexagonal intercalated antiperovskites, most of which have been found in pyrometamorphic rocks of the Hatrurim Complex, Israel. Three members of this supergroup: nabimusaite, gazeevite and zadovite, were identified for the first time in altered carbonate–silicate xenoliths from the Caspar and Scherer quarries, Bellerberg volcano in Germany. Present work focuses on the chemical, structural and spectroscopic investigation of these minerals and their correlation with holotype counterparts. The apparent differences are mainly related to the chemical composition, types of substitution in the tetrahedral and antiperovskite layers within the crystal structure, and position of bands in the Raman spectra. In the Bellerberg volcano xenoliths, the crystallisation of nabimusaite and gazeevite is caused by high-temperature alteration of early mineral associations (clinker-like phases) and their reaction with melt or gas generated by volcanic activity. In turn, the formation of zadovite is related to the Ba-rich silicate melt that filled the intergranular space between the rock-forming minerals.

Barium melilite – bennesherite, Ba2Fe2+Si2O7, known only from pyrometamorphic rocks of the Hatrurim Complex in Israel, has been recognised in a carbonate–silicate xenolith from the Bellerberg volcano area in Germany. The empirical formula of the German specimen is as follows: (Ba1.32Ca0.43Sr0.23Na0.05K0.02)Σ2.05(Fe2+0.79Ti0.06Mg0.05Al0.04Mn0.03Zn0.01)Σ0.98Si1.97O7. The Raman spectrum of bennesherite exhibits the presence of the main vibrations related to Fe2+O4 tetrahedra and disilicate Si2O7 groups at the T1 and T2 sites, at 589 cm–1 and in the range 618–673 cm–1, respectively. Detailed spectroscopic analyses performed for bennesherite in two different and random orientations confirm the reduction of bands intensity and the number of some components in several spectral ranges. Moreover, the presence of a heavy Ba atom indicates a decrease in band frequencies compared to melilites with Ca at the X position. A single-crystal X-ray diffraction experiment, despite attempts, could not be carried out due to the poor quality and small size of the bennesherite crystals however, a combination of composition and Raman data allowed for accurate phase identification. Detailed mineralogical investigations distinguished rare Ba minerals in association with bennesherite, such as walstromite, fresnoite and celsian, along with various ferrous melilites. Some of the detected phases are described from xenoliths of the Bellerberg volcano for the first time. The uniqueness of the Bellerberg volcano mineralisation is reflected in the interaction of alkaline magma with xenoliths of different compositions, which suggests that this locality still deserves attention as a source of new and unique minerals.