You will find that a gram of 30 mesh gold flakes won't get picked up by a gold detector, where a 1/10 gram nugget will. When you have a lot of small flakes, they don't add to the signal - rather they react independently. This is one reason that small gold chains are so hard to detect - there may be a lot of links, but the whole mass does does not count, its the size of the individual pieces that trigger a result.
Small bird shot is also a good gold target subsitute. Gold and bird shot give the same reaction as far as your detector is concerned.
Also once you get a small nugget to respond - take that same gold nugget and hold it still, right in the center of your search coil - you will notice that the gold will no longer read as anything - this is because you have a motion detector - your coil has to be moving to detect anything. I often demonstrate this with a 7/10 gram nugget I have - Its supposed to work this way.
This is why I consider it a good idea to learn how to detect for coins - there are hundreds of times more of these for you to hone your pin-pointing skill with than there is gold nuggets for you to find. The last thing you want to do is be out detecting and not be able to find your targets (I dig until I find all of them, trash or not).
Gold Detecting is a lot harder than coin or relic detecting - it requires an exceptional amount of patience and perseverance. Your targets are often tiny noises in your headphones - if you are not paying attention, you'll miss them. You will dig a lot of trash and it won't bother you (because sometimes what appears to be a deep iron target is gold).
If you are not using a quality set of headphones (I use Gray Ghost headphones), you will get a lot of exercise, but will likely only ever find trash.
I find that (for where I search - which includes areas with tailings dumps and large piles of dredge overburden) that a small DD coil is better than a larger coil. The smaller coil responds better to small gold, and also brings a smaller footprint (ie. I see less trash).
