Ancylite-(Ce) from quartz-calcite-chlorite veins in phyllite of the Opava Mountains (SW Poland)

Ancylite-(Ce) occurs in quartz-calcite-chlorite veins crosscutting the foliation of phyllite in the Dewon Quarry in the foothills of the Opava Mountains of the eastern Sudetes, south-west Poland. Irregularly shaped grains of ancylite are up to 67 μm long and 22 μm wide. The compositional range of ancylite, determined by electron microprobe, is expressed by the empirical formula: (Sr0.65-0.55Ca0.19-0.14Fe0.03-0.00)∑0.87-0.69 (Ce0.58-0.50Nd0.26-0.22La0.26-0.21Pr0.06-0.05Sm0.05-0.04Gd0.07-0.03Dy0.01-0.00)∑1.29-1.05 (CO3)2(OH1.07-0.99F0.22-0.0.06)∑1.29-1.05· 0.95-0.93H2O. Ancylite crystallized directly from CO2-rich hydrothermal solutions as the last mineral in the veins following precipitation of calcite. The solution temperature, estimated using various chlorite geothermometres, was in the range of 260-340°C.