Acta Musei Moraviae

Celsian and its mineral association from the ore deposit Zlaté Hory – East (Czech Republic)

Rich occurrence of celsian which forms a locally predominant part of the mineralization and also appears here as well-developed short prismatic crystals, up to 2 cm in size, in fine-grained black-gray sphalerite and other sulfides, was recently found in the mining block B 301 at the second exploration level of the Zlaté Hory – East deposit (Silesia, Czech Republic). Crystals and aggregates of celsian are usually clearly zonal, but Ba (0.73–1.06 apfu) is always dominant in the position of alkali metal, accompanied by the presence of K (up to 0.23 apfu) and Na (up to 0.07 apfu). Celsian is monoclinic, space group I2/c, with the unit-cell parameters refined from X-ray powder diffraction data: a 8.6391(13), b 13.0558(12), c 14.416(2) Å, β 115.158(9)° and V 1471.8(4) ų. Celsian is accompanied by abundant sphalerite and pyrite, as well as chalcopyrite, galena and pyrrhotite. From gangue minerals, in addition to quartz, chlorite, dolomite, and more rarely siderite, baryte, fluorapatite and monazite-(Ce) were observed. The observed mineral association with celsian was formed during the Variscan metamorphic reworking of the original stratiform mineralization, the composition of which included baryte and sulfides in addition to siliciclastic material. In the younger stage, tiny thin veins were originated in the celsian-sulfide mineralization, which are formed by sulfides (pyrrhotite, galena and sphalerite) or minerals from the chlorite group. The primary mineralization is significantly affected by weathering processes in the conditions of the supergene zone in-situ; it is the deepest occurrence (85 m below the present surface) of supergene processes detected in this ore district. Occurrences of predominant limonite accompanied locally by hemimorphite, aurichalcite, covellite, minerals from the anglesite – baryte solid solution series, brochantite, linarite, cerussite and gypsum were recorded here. Primary chlorites and part of the celsian were also altered by supergene processes.