If you aren't with someone who knows the area, you can easily miss a likely digging area as most of the surface float has been picked up already. The collector who finds a large pocket of fine aquamarine is indeed extremely fortunate. But there are many good areas where a reasonable amount of scratching and shoveling should result in a few decent small smokies or beryl matrixes, maybe even some fluorite or one of the other desirables or a chip or two of aquamarine. Success often depends on knowing a bit about the geology, as well as experience. Clear areas large enough to cut over a couple of carats clean are uncommon.
Most crystals have veils or inclusions or etching which prevent maximum yield.
The largest stone I have cut from here that was eye-clean is about 9 carats. I have seen several specimens that would yield stones up to 15 or 20 carats or more, some of which are very fine deep blue. If you find a perfect terminated crystal however, it is usually considered a sacrilege to cut it into gemstones. They are beautiful in their own right and much scarcer than broken chunks or pieces or damaged crystals which can be cut. I have seen gorgeous specimens from here with phenacites or fluorites implanted on the termination or side faces of the aquamarine crystals.