At the Yankee Girl showing, Helikian Aldridge Formation (Purcell Supergroup) quartzites hosts a hornblende-diorite sill of the Proterozoic Moyie Intrusions. The sill hosts quartz veins and stringers carrying pyrite and chalcopyrite with minor galena and sphalerite. The major vein is 1 to 2 metres wide and strikes 330 degrees with 65 degree west dips.