gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1960.032.251.07 Ages of Uraninite from two British Localities Darnley A. G. M.A., Ph.D., A.M.I.M.M. Atomic Energy Division, Geological Survey of Great Britain, Young Street, London W. 8 Smith G. H. Chandler T. R. D. National Chemical Laboratory, Teddington, Middlesex Dance D. F. Preece E. R. Atomic Energy Research Establishment, Harwell, Berkshire 12 1960 32 251 654 658 Copyright © 1960, The Mineralogical Society 1960 Summary

Uraninite from Geevor Mine, Cornwall, has been analysed by the complete lead method and an age of 290±7 million years has been accepted. Similar studies of uranium from Tyndrum Mine, Perthshire, give an age of 230±8 million years. The significance of the results is briefly considered.