The study presents fifteen oxygen-bearing secondary minerals of bismuth from the north-eastern part of the Variscan Karkonosze granitoid pluton in the northern zone of the Bohemian massif. The minerals were investigated by optical, electron microprobe, classic chemical, XRD, IR absorption and fluid inclusion methods. The late, very low temperature epithermal solutions most probably caused formation of sillénite, kusachiite, bismoclite, bismutite, beyerite, kettnerite, pucherite, schumacherite, namibite and eulytite. Solutions dominated by supergene (meteoric) waters were the parents for bismite, russellite, koechlinite, ximengite and walpurgite. The paper also contains information on early research on the investigated minerals.

Twenty silver minerals of the sulphide, arsenide, selenide, telluride, sulphosalt and chloride groups were found in 13 locations in the Variscan Karkonosze granitoid pluton. Previously only one of these minerals was known from this area. The findings include species characterized in publications as rare or exceptionally rare, e.g., muthmannite and tsnigriite. They occur in pegmatites and quartz veins; their parageneses are described. The studies include determination of chemical compositions, formulae calculations and recording of XRD patterns. Inclusion studies in paragenetic quartz indicate that they crystallized from epithermal fluids with a common but low component of CO ₂. The results suggest that the minerals formed from trace elements (Ag included) in the Karkonosze granitoid due to very local degrees of recrystallization of the host granitoid.