Minerals with a palmierite-type structure. Part I. Mazorite Ba₃(PO₄)₂, a new mineral from the Hatrurim Complex in Israel

Abstract

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.

Minerals with a palmierite-type structure. Part II. Nomenclature and classification of the palmierite supergroup.

“…Its formation is related to the crystallisation from residual melt enriched in incompatible elements that fill interstices between the main rock-forming minerals of paralava (Galuskina et al , 2017). The crystal structure of synthetic Ba orthovanadate was investigated in detail (Süsse and Buerger, 1970; Morris et al , 1977; Mugavero et al , 2008; Azdouz et al , 2010), whereas for its natural counterpart enriched in P 5+ , the single-crystal X-ray diffraction investigation was carried out only recently (Juroszek et al , 2023). Previously, only electron back-scatter diffraction (EBSD) data were available (Galuskina et al , 2017).…”

“…Mazorite Ba 3 (PO 4 ) 2 , the P-analogue of gurimite, is a new mineral that was recently found as an accessory phase in coarse-grained gehlenite–rankinite paralava in the Hatrurim Complex in Israel (IMA2022–022; Juroszek et al , 2023). The similarity of crystallisation conditions between mazorite and gurimite, as well as the relationship with the associated Ba-bearing minerals like celsian, hexacelsian, walstromite, fresnoite, zadovite and barioferrite, in both cases, confirm the high-temperature formation of this phase.…”

“…The present work describes the nomenclature and classification of the palmierite supergroup approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA-CNMNC Proposal 22-L, Bosi et al ., 2023). The proposal to the IMA and the requirement for developing the palmierite supergroup classification are related to the discovery of a new mineral, mazorite Ba 3 (PO 4 ) 2 (IMA2022–022; Juroszek et al , 2023). The approval of the nomenclature and the classification of the palmierite supergroup allows us to not only classify the five minerals into one structural supergroup, but also to formally use the name already firmly established in the literature.…”