A significant discovery of pitchblende mineralisation was made recently by Departmental prospectors at the abandoned workings of the Shamrock mine located in the Yudnamutana Copper Mining District. The occurrence comprises two separate well-defined lodes within a spotted schist bordering the actinolitic marble belt of the Torrensian Series, Adelaide System. The lodes, identified respectively as the Shaft prospect and the Valley prospect, lie along a shear zone in the southern limb of a tightly folded and overturned syncline. Radiometric assays of channel samples range from 2 to 26 lb U3O8 per ton, and indicate a probable average grade of about 8 lb U3O8 per ton. Subsurface exploration by conventional mining methods is recommended.