Mineral separates from the main lodes and mine sequence rocks at Broken Hill have been analysed using the U/Pb and Pb/Pb methods. This investigation had four main objectives and conclusions: to determine 1) the age of crystallization of apatite-the apparent 1595 m.y. ages for monazite and sphene and the 1550-1575 m.y. age range for apatites are most simply explained as cooling ages, the Broken Hill Block remaining above 600oC for 60-70 m.y. after metamorphism; 2) the age of source material of the mine sequence rocks-zircon U/Pb ages were reset during the granulite facies metamorphism at 1663 m.y., thereby obscuring the source age; 3) the possible volcanic or sedimentary parentage of the mine sequence rocks-zircons from the gneisses have undergone a complex history, judging from their morphology (unlike zircons in felsic to intermediate volcanics) and are not simply derived in a single-stage process from a volcanic source; and 4) the isotopic homogeneity of the main sulphide lenses-sphalerites and pyrrhotites show uniform lead isotope ratios throughout the ore-body because of the presence of (inseparable) galena inclusions.-G.J.N.