True iron-nickel meteorites will have a strong attraction, so that would likely rule it out. The rust definitely sounds on target, but another strange thing is that you describe it as being very light, when in fact iron-nickel meteorites will be heavy.
To test conductivity, use an ohmmeter. Take a look at this link:
If you don' have access to an ohmmeter, you can use a battery operated flashlight and wires and try running one of the wires through the stone to see if the electricity passes through.