New data on halloysite of Ukraine

A rare chromium-containing variety of halloysite has been identified in the weathering crust of the Derenyukhinskiy gabbro-peridotite massif. Its remarkable features are blue colour, Cr2O3 content in the amount of up to 2.47% and luminescence under ultraviolet radiation. The study of the excitation and emission spectra showed that the maximum luminescence of this variety of halloysite occurs when irradiated with waves with a length of 367 nm, and the emission wavelength corresponds to the region of 390-500 nm, with a maximum at 424 nm. The studied sample was actually a mixture of two mineral species: halloysite (10Å) and halloysite (7Å) or metahalloysite. Aluminian chromite was identified in association with them, and impurities of kaolinite, clinochlore, quartz and goethite were detected. The formation of the mineral aggregate was due to chemical weathering of primary silicates and oxides, which were part of the rocks of the Derenyukhinskiy massif. Originality. Halloysite has been identified for the first time in the weathering crust of the Derenyukhinskiy gabbro-peridotite massif (Middle Pobuzhzhya). It was found that chromium-containing halloysite exhibits violet luminescence under ultraviolet radiation. The fluorescence spectrum of the mineral also has been studied.