Many veinlets in carbonate rocks considered as open crack fillings, are the result of recrystallization (dashed veinlets formed by the shear, whitened veinlets). Synsedimentary and early diagenetic veinlets may be folded in a soft sediment deformation or deformed by brittle fragmentation. They may also fill desiccation cracks, bedding - parallel joints and synsedimentary cracks with internal sediment (microdykes). Synaeretic cracks in bedded silicites and nodular cherts can be filled with calcite partially infiltrating the still reactive silica masa (pearl-string type veinlets, bordered veinlets), filled by chalcedony, or can disappear being healed by neighbouring silica mass. Relative dating of veinlets with regard to the formation of authigenic minerals, formation of chert nodules, conglomerate deposition, calcite twinning, microstylolites etc. is possible. Authigenic quartz, feldspars, pyrite, illite, baryte, fluorite and galena found in calcite veinlets are mentioned. From the commonly occurring dedolomitized saddle dolomite in calcite veinlets, the burial depth of the Krizna Nappe was estimated.