engleski

A new crystallographic feature of barite from the Balkan peninsula

Eight different habit types of barite crystals which could be classified in four essentially different groups were determined by morphological analysis: Tc group –barite crystals tabular on basal pinacoid {001}; Ea group – barite crystals elongated in [100] direction; Eb group – barite crystals elongated in [010] direction; Ec group barite crystals elongated in [001] direction. By comparative analysis of the unit cell dimensions of barite specimens, represented by different habit types, it was determined that the value of unit cell parameter decreases in direction of crystal elongation. The value of unit cell parameter increases in the shortening direction. Analysis of the recticular density of the crystal form faces showed that the density of atomic arrangement in the barite structure is enlarged on the faces from the elongation zone in relation to the density atomic arrangement on the terminal faces. As in the case of the tabular barite crystals the density of the atomic arrangement on the faces from the shortening zone is decreased in relation to the density of the atomic arrangement on the terminal faces. A low content of Sr2+ ions and their distribution in the crystal lattice may be a reason for the variation of the lattice constants.

Barite; habit types; unit cell dimension; reticular density; Balkan peninsula

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