Rex, In Oz we have areas that are thousands of acres of quartz lying on top of the ground but there is NO gold there. My experience with black sand showed that the gold associated with it was very fine. A detector would not pick this type of gold up. However the detector may be used to locate black sand deposits so that other methods may be used to extract the gold IF it is there.
My suggestion to you is : If there are no old timer workings or prospects where you have all this quartz etc, then there is probably no gold there. Start by looking where the old timers found gold. Their lives depended on finding gold so they didn't waste time in non productive areas. It dosen't matter if others have been there before you as this is where we learn the signs of what to look for. Once you do find a little nugget, and it probably will be a little nugget, Then take a good look at where you dug it out from. Look at the soil or gravel type it is lying in, Look around you. Is it on a slope or a gully. If it is on a slope, there may be more above you. If it is in a gully take extreme care as they can be quite deep and easy to miss. Has it been dug out onto a heap by the old timers? If so check the heaps very carefully. But most of all be patient and confident that if there is one there for you, you are not going to miss it.
I reiterate... Go where the old timers found gold. That is your best chance.
The Cat