you could try ebay
But that is Shakey
because people wont be able to test it's Purity from Pictures.
Your best bet would be to talk to
a Local Gold Buyer & see if they
buy Raw gold,
or know somone who does.
or contact the GPAA
or local GPAA Chapter.
for advice on selling
I guess that depends on what you think it is cracked up to be.
Right now with Gold at $1200.00 an oz. spot, you should easily get $1,000.00 an oz. depending on the purity of course.
Large nuggets are worth even more than that per oz. due to their rarity.
I take mine to a local jeweler who pays me 90% of spot price.
Midwest Refineries pay 95% of spot ( day of receipt) for pure gold. http://midwestrefineries.com/
*Note gold is bought and sold using troy wt. A troy oz. is 31.1 grams not 28.3 grams as in an avoirdupois oz.