Qeltite - the first terrestrial high-temperature mineral with a langasite-type structure from the pyrometamorphic rocks of the Hatrurim Complex

Qeltite (IMA2021-032), ideally Ca3Ti(Fe2Si)Si2O14, was found in gehlenite-rankinite-wollastonite paralava from a pyrometamorphic rock of the Hatrurim Complex at Nabi Musa locality, Judean Desert, West Bank, Palestine. It generally occurs as light-brown flattened crystals up to 40-50 mu m in length and less than 5 mu m in thickness. Its aggregates reach 100-200 mu m in size. Its empirical crystal chemical formula based on 14 O is: (Ca2.96Sr0.02Mn0.01)(Sigma 2.99)Ti4+(Fe1.593+Si0.60Al0.43Ti0.384+Cr0.01)(Sigma 3.01)(Si1.99P0.01)(Sigma 2)O-14. The strongest reflections in its calculated X-ray diffraction pattern are [d, angstrom, (I, %), hkl]: 3.12, (100), 111; 2.85, (61), 201; 2.85, (48), 021; 2.32, (45), 211; 6.93, (31), 100; and 1.81, (30), 212. Qeltite is trigonal and crystallises in the noncentrosymmetric P321 space group, with a = 8.0077(5) angstrom, c = 4.9956(4) angstrom, V = 277.42(4) angstrom(3) and Z = 1. Its microhardness VHN25 is 708(17) kg/mm(2) and its hardness on the Mohs scale is similar to 6. Its calculated density is 3.48 g/cm(3). It was found in fine-grained mineral aggregates within coarse-grained main minerals of rankinite-gehlenite paralava with subordinate wollastonite, Ti-bearing andradite and kalsilite. In these aggregates, the mineral is associated with khesinite, paqueite and pseudowollastonite, indicating a high-temperature genesis (similar to 1200 degrees C). Its crystallisation can be compared with the crystallisation of minerals containing refractory inclusions in meteorites.