Ground magnetometer surveys were carried out by the writer over typical portions of the geomagnetic anomalies located at the North Billeroo dam area and adjacent to the Alconie dam to determine their cause. Inspection of these areas showed that the anomalies were due to low grade magnetite and haematite bearing metasediments. The writer considers that the formation represents the dynamothermal metamorphic equivalent of archaean ferriginous shales in which the iron minerals are syngenetic. The north Billeroo geomagnetic anomalies appear to represent the same geological horizon as the Billeroo iron ore deposits. The latter have been mapped by Lockhard Jack in 1922. Based on the results of recent geological and geophysical surveys, the iron ore reserves at the Billeroo Dam appear to be of a higher order than the estimates of 1922. The writer recommends that ground magnetometer surveys be carried out in the Ballara and Outalpa areas where geomagnetic anomalies are located. It is possible that there may be economic iron ore deposits at shallow depth and concealed by alluvium and glaciofluvial beds.