Crystal-chemical characteristics of barite from Zlatar (Serbia)

Rocks of the Diabase-hornfels formation built great part of Zlatar and its surrounding area. Into the composition of this formation enters: sandstones, siltstones, claystones, hornfels, and fewer limestones, as representatives of the sedimentary rocks; whereas magmatic rocks consist from diabases, spilites, gabbros, and less serpentine. It is very interesting occurrence of barite in this formation, whose outcrop was discovered at the area of about 100 m2. In this paper barite was crystallographicaly and chemically characterized. Observed values of the inter-planar spacings (d), as well as calculated unit cell dimensions of: a = 7.146(1) Å; b = 8.869(1) Å; c = 5.446(1) Å; and V = 345.14(8) Å3; are something smaller regard to the literature data which are adequate to “pure“ barite. Such is consequence of partially (about 2 %) isomorphic substitution of Ba2+ with Sr2+ and Ca2+ cations which have smaller ionic ratio. Presence of Pb2+ cations in the structure is neglected, so the crystal-chemical formula of the investigated barite could be presented as: (Ba0.99Ca0.01Sr0.01)1.01S1.00O4