Deynekoite, Ca9□Fe3+(PO4)7 (R3c, a = 10.3516(3)Å, c = 37.1599(17)Å, V = 3448.4(3)Å3 and Z = 6), a new mineral of the merrillite group was found in the contact facies of paralava of the Hatrurim Complex in the Daba-Siwaqa pyrometamorphic rock field, Jordan. The paralava, consisting of diopside, tridymite, anorthite, wollastonite and fluorapatite, is enriched in Fe-bearing phosphides and phosphates at the contact with the altered country rock. Cristobalite overgrowing tridymite has a fish-scales texture indicating that temperature of paralava could have reached 1500°C. Deynekoite with empirical formula (Ca8.90Na0.11K0.02)Σ9.03(Fe3+0.62Mg0.30Al0.05)Σ0.97P6.98V5+0.05O27.70(OH)0.30 forms transparent, light-yellow or light-brown grains up to 30–40 μm in size. Microhardness of deynekoite, VHN25 = 319(29) kg/mm2, corresponds to Mohs hardness = 4.5. Its density was calculated as 3.09 g⋅cm–3 on the basis of its empirical composition and structural data. Deynekoite is uniaxial (−), its refractive indices are ω = 1.658(3), ɛ = 1.652(3) (λ = 589 nm), and pleochroism is not observed. The formation of phosphides on the boundary of the paralava and country rock is connected with carbothermal reductive reactions and realised at temperatures above 1300°С. With decreasing temperature and increasing oxygen activity, phosphides are replaced by Fe2+-bearing phosphates. Deynekoite, which contains Fe3+ (substituting for Fe2+-phosphates) and a small amount of water, formed at temperatures of 600–800°C.

Fluoralforsite, ideally Ba5(PO4)3F, (space group P63/m (#176), Z = 2, a = 10.0031(2) Å, c= 7.5382(2) Å and V = 653.23(3) Å3), is a new mineral species of the apatite group – a Ba-analogue of fluorapatite and a F-analogue of alforsite. It was discovered in rankinite paralava filling cracks in pyrometamorphic gehlenite hornfels near the tributary of wadi Zohar and Gurim Anticline, Hatrurim Basin, Negev Desert, Israel. Fluoralforsite occurs in small intergranular spaces between large gehlenite and garnet crystals and in enclaves inside large rankinite crystals with other Ba minerals such as walstromite, zadovite, bennesherite, gurimite, mazorite, barioferrite and baryte. It forms tiny transparent, colourless crystals up to 50 μm with a white streak and a vitreous lustre. The cleavage was not observed. It exhibits a brittle tenacity and a conchoidal fracture. The estimated Mohs hardness is 4–4½, and its calculated density is 4.57 g/cm–3. Fluoralforsite is uniaxial (–) with refractive indices (589 nm) nω = 1.689(3) and nɛ = 1.687(3). The empirical crystal-chemical formula for the holotype calculated on the basis of 8 cations is: (Ba3.81Ca0.97Na0.07K0.05Sr0.05Fe0.05)Σ5(P5+2.32V5+0.29S6+0.22Si0.17)Σ3O12(F0.85Cl0.13)Σ0.98. The crystal structure was refined from single-crystal X-ray diffraction data with R1 = 0.0192. The structural investigation indicated an ordered arrangement of Ba/Ca at the M1 site within individual columns running along the c-axis, but a disordered distribution among adjacent columns throughout the structure, which enables the maintenance of the P63/m space group. Fluoralforsite was formed at the final stage of crystallisation as a result of a reaction between the primary mineral assemblages and residual melt.

The intergrowths of Fe-rich corundum + Al-rich hematite + spinel + hibonite have been found as an assemblage in a plagioclase-clinopyroxene rock (paralava, former hornfels) at the Hatrurim Basin, Hatrurim combustion metamorphic Formation. Most spinels show oriented exsolution structures and vary from (Mg0.75${\rm Fe}_{{\rm 0}{\rm. 25}}^{2 +} $)(Al1.80${\rm Fe}_{{\rm 0}{\rm. 20}}^{3 +} $)O4 (with exsolutions) to (Mg0.77${\rm Fe}_{{\rm 0}{\rm. 23}}^{2 +} $)(Al1.95${\rm Fe}_{{\rm 0}{\rm. 05}}^{3 +} $)O4 (homogeneous) indicating a tendency towards magnesioferrite and magnetite, and enrichment in NiO (up to 1.9 wt.%) and ZnO (up to 1.4 wt.%). Hibonite is Ti rich (TiO2 > 8 wt.%) and close to CaAl9Fe3+(Mg,Fe2+)TiO19. Corundum varies in Fe2O3 (4.2–11.8 wt.%). Hematite is also inhomogeneous and contains oriented exsolution structures of corundum. It shows variable concentrations of TiO2 (0.7–5.6 wt.%), Al2O3 (0.7–8.6 wt.%), Cr2O3 (0.2–1.5 wt.%), V2O3 (0.1–1.0 wt.%) and MgO (0.3–2.0 wt.%). Crystallization of this specific assemblage is assumed to be at 1000–1200°C using evaluations for the corundum hematite pair with reference to published experimental data. The active role of superheated oxidised volatiles is suggested during both crystallisation of this corundum-bearing association and host-rock transformation (melting event for hornfels → paralava).

This is the first description of rare minerals found in paralavas from a recently discovered combustion metamorphic complex in the Choir–Nyalga basin, Central Mongolia. The identified minerals contain strongly variable concentrations of Si, Ti, Mg, Fe2+ and Fe3+and most commonly have compositions intermediate in a series from kuratite Ca4Fe102+Ti2O4[Si8Al4O 36] and rhönite Ca4(Mg, Fe2+)8Fe23+Ti2O4[Si6Al6O36] to low-Ti kuratite and unnamed Ti-free Fe2+-analogue of rhönite Ca4Fe82+Fe43+O4[Si8Al4O36]. The minerals crystallized in residual Si-Al-K and Si-Al-Ca-Fe immiscible melts after spinel, anorthite–bytownite, melilite, Al-clinopyroxene ± Mg-Fe olivine, together with Fe3+-bearing hercynite, Ca-rich fayalite, kirschsteinite, pyrrhotite ± native iron, wüstite, magnetite, celsian, hyalophane, Ba-orthoclase and fresnoite, but before nepheline± kalsilite, and later sulfates, carbonates, an unidentified 'X-mineral' close to Al- and Fe-rich tobermorite and goethite. Micro-Raman spectroscopy of kuratite shows five bands near 133–155 (strong), 399–401, 545–566, 684–693 (strongest) and 828–839 cm–1.

The kuratite-bearing Nyalga paralavas have bulk compositions with MgO/(MgO+FeO+Fe2O3), mol.% ∼0.5 and a CIPW normative ratio of Ne/(Ne+Lc) = 0.23–0.76. Minerals of the rhönite–kuratite series formed during paralava crystallization at ∼1100°C.The diversity of the paralava mineral assemblages might result from local composition variations of Ca-rich silica-undersaturated melts derived from Fe-bearing carbonate-silicate sediments which were affected by nearby coal combustion sources at reducing conditions (IW-WM-QFM buffers) and at a nearly atmospheric pressure.