A detailed gravity survey over the Iron Blow prospect has revealed areas of low gravity and faults associated with the old mine. The mass deficiency in this area is 71,500 tons, probably representing porous leached material, which may extend to at least 100 feet below ground level. A large circular positive anomaly was delineated around drill hole B.H.I. and this anomaly has an excess mass of 127,500 tons for a radius of 180 feet. The density of this material was estimated to be higher than that expected for dolomite, which was encountered in the drillhole. Numerous faults have been delineated, the principle one being, the tectonic boundary of the diapir on the western side of the area. A residual gravity map was produced from the Bouguer gravity data using a 4th Order Polynomial surface and the regional and residual contours of the mine area are displayed in this report.