kenfer,
if all the known gold were tossed into one pile just like it came out of the dirt only 2% of it would be larger than dust. chunky gold, or pickers if you like, are very small nuggets. viewed through a magniving glass they look just like the larger nuggets, and command a higher price than flour gold, or gold dust. they are used mostly in jewelry in their natural state. for instance, take one and put a post on it....you got a tie tack or pierced earring. cuff links the same thing. many are added to rings etc. just like they came out of the ground. usually, you can figure on paying 10% over spot for anything you can pick up between your fingers. if it has a little quartz stuck to it the price goes up. the larger the nugget the higher over spot the value. thats the kind of gold i have offered in a quantity that the same gold, as dust, would be more than enough to sell to buy the detector. i will not send pickers off with dust to a refinery where it all gets cooked down the same, but i will gladly pass it on to someone else who can do with it what they like. pennies are pennies, but your '09 vdb, or your copper 43....now thats a PENNY. gold is gold but not necessarily a nugget.
i hope that explains it. if not check out some sites that sell nuggets and do the math. there are other reasons but not that i will take your time with now. if you don't understand now i will gladly give you face value for any U.S. coin you dig.
thanks for the interest.