A very sensitive coil, as some 1 gram nuggets or smaller due to it's size. Usually, smaller coils are used for those size targets. Some say DD coils are superior in higher mineralized soils. Some discrimination is an asset too! being able to id iron as such saves you a lot of wasteful digging. Generally, a higher frequency machine over a lower frequency will work better for smaller targets.
Most manufacturers sell single frequency detectors designed and tweaked for gold. Now, should you require more depth, PI (pulse induction) is the way to go. Not only will they go deeper, they will also punch through highly mineralized soils, where single frequency machines tend to struggle. But, as of now, PI machines are limited to any discrimination.
Go look up some gold searching forums which have sub forums on detecting with a metal detector.
Good luck!
PS - Coils will not pick up flour gold. But you can however, run your detector "hot" and pick up areas where the iron is concentrated, an area which probably has a greater chance of having some gold.