I was figuring out how much its worth. Its about 330,000$ US at a yesterday rate of 1700$/oz. .
Gold occurs in serpentinite and in quartz 'feldpars called "Pegmatites". The Calif gold rush started as a complete accident . The clay that Set mentioned was a center of a serpentinite belt that is unique to Calif, SC, Va, Md, Pa and NY. Most of these areas have had minor "gold rushes" in thepst but the really big claims , like the Nevadan, Mexican, Brazilian, South African, Phillipine and , the High Sierran, the Canadian SHield, are all Quartz fold belts.
Ill bet that the nugget this dude found was from a serpentinite. The one that Set posted was all gnarly and the Oz one was smooth. The gnarly ones are gotten out by soaking in aqua regia and Hydroflouric acid (Quartz dissolves in HF. So the gold that remains is actually the little cubby hioles of the metal in veinlets and cracks that get filled with gold in superheted water.
VERA cool. Its got a bigger value on the collectos market (There are a few big rock collectors out there that pay millions for one specimen of so,ething very rare or beautiful)