Does the Falcon sound off as you approach the target and continue to increase in tone until you reach your item in question? Or, does it give a signal as you cross your item but blank as you cross it, or does the signal increase as you pull away from your item?
You've been given the instructions on how to do a specific gravity test; that will tell you something.
Does your item conduct an electric current (voltmeter)?
I'd do the streak test on a piece of unglazed porcelain tile (Google it) as well as has been suggested.
If you have the remotest idea it could be a nugget, do not whack it with a hammer!
All the best,
Lanny