  The rate of secondary charm-quark-pair production has been measured in 4.4
million hadronic Z0 decays collected by OPAL. By selecting events with three
jets and tagging charmed hadrons in the gluon jet candidate using leptons and
charged D* mesons, the average number of secondary charm-quark pairs per
hadronic event is found to be (3.20+-0.21+-0.38)x10-2.
