Reference: ▪ Drábek;, M., Frýda J., Šarbach M., Skála, R. (2017): Hydroxycalciopyrochlore from a regionally metamorphic marble at Bližná, Southwestern Czech Republic. Neues Jahrbuch für Mineralogie - Abhandlungen: Journal of Mineralogy and Geochemistry, 194, 49-59.
Abstract: We describe an unusual occurrence of hydroxycalciopyrochlore in marble exposed in the Václav graphite mine at Bližná, southern Czech Republic. Roundish grains attain up to 3 cm, and euhedral crystals are up to 2 mm across. An empirical formula, calculated on the basis two B atoms per formula unit (pfu), is: (Ca0.48Na0.02Mg0.06Mn0.01Y0.06ΣREEs0.27Th0.27U0.01)Σ1.12 (Nb1.06Ti0.79Fe0.14W0.01)Σ2 (O4.96OH1.04)Σ6(OH)0.81·H2O. The associated minerals, in addition to the rock-forming minerals calcite, phlogopite and edenite, include ilmenite, magnetite, euxenite, uranoan thorite, rutile, zircon, molybdenite, chalcopyrite, galena, sphalerite, pyrite, pyrrhotite, barite and apatite. This is the first occurrence of a pyrochlore-group mineral in regionally metamorphosed marble. The assemblage is considered to represent a metamorphosed carbonate-dominated sediment containing evaporitic horizons and volcanic detritus. Now give the reader an explanation, what makes it carbonatite-like?