Sircorp I do not understand how you have going from an optimist to a pessimist in a matter of days, please make rational posts for all is dmn prospectors!
Here is an excellent read about understanding gravity surveying. It gives densities for different minerals etc definately a tool I will put away for analysis of other surveys in future. http://www.scintrexltd.com/downloads/GRAVGUID.pdf
Here is a couple of gravity surveys from other companies http://www.maximusresources.com/asx_projects/2008/mxr_asx20080423_sml.pdf