Rubinite, a garnet with the ideal formula Ca3Ti3+2Si3O12, is an indicator of super-reduced conditions and has been found recently in refractory inclusions in a few CV3 chondrites. We discovered rubinite in phosphide-bearing breccia from the pyrometamorphic Hatrurim Complex, Negev Desert, Israel. Aggregates of phosphide and native iron are concentrated at the boundary of thermally altered sedimentary xenoliths encased in flamite–gehlenite paralava. Rubinite, with the average empirical formula (Ca2.97Mg0.02Fe2+0.01)Σ3.00(Ti3+1.10Al0.44Ti4+0.37Mg0.08Cr0.01)Σ2(Si2.71Al0.29)Σ3.00O12, was found in a small xenolith composed of hydrogrossular, tacharanite and calcite, and containing relics of high-temperature minerals such as pseudowollastonite, cuspidine, gehlenite, baghdadite, barringerite, murashkoite, osbornite, paqueite and oldhamite. For the first time, the structure of rubinite, with the composition (Ca2.99Mg0.01)Σ3(Ti3+0.78Al0.62Ti4+0.43Mg0.17)Σ2(Si2.74Al0.26)Σ3O12, has been refined. Its unit-cell parameter a = 12.0193(4) Å, is significantly smaller than that of the synthetic analogue of Ca3Ti2Si3O12, 12.1875 Å. In the rubinite Raman spectrum weak bands corresponding to the vibrations of Ti4+–O in the (TiO6)8– octahedra: 610 cm–1 ν1(TiO6)8– and 438 cm–1 ν4(TiO6)8– are present in addition to the bands related to Si–O and Al–O vibrations in the TO4 tetrahedra. Rubinite forms a thin reactive rim (<10 μm) on pseudowollastonite grains. It probably formed during a sharp increase in rock porosity in the course of natural clinkerisation of sedimentary xenoliths caused by the thermal impact of the paralava. The high porosity increased the effect of reductive gases on the rocks, which were by-products of pyrometamorphism. The brief appearance of super-reduced conditions defined the formation of the Ti3+-bearing minerals osbornite and rubinite. Paqueite, Ca3Ti4+(Ti4+Al2)Si2O14, which crystallised in a thin melting zone of xenolith at the boundary with the paralava, does not contain Ti3+.