Keyword "OPAL" in:
Recent minerals in the Bedřichov water supply tunnel in Jizera Mts. – an example of uranium release from the Jizera granite
Klomínský,J., Veselovský,F., Malec,J., volume 46, 2013 (GRR for 2012), pages 214–219
pdf (1 MB)
New finds of cavity minerals during the mining of neovolcanic rocks, Mariánský vrch in Ústí nad Labem (N-Bohemia)
Vlačiha,V., volume 31, 1998 (GRR for 1997), pages 129–129
pdf (0.06 MB)

