waldronate, You are not stomping on me. This is a complex subject and more views are welcome. The area I am in (west central Georgia) is quite different from your neck of the woods. The geologic processes are quite different but produce similar results. I live on the fall line that runs across central Georgia roughly east-west. South of us is "new" land made up of the coastal plains. It is sediment formed by the erosion of the ancient Appalachian mountains. It is good farm land as well as a good source of clays. Moving north of the fall line is the piedmont. The basement rocks are exposed revealing sedimentary and igneous gneiss. There is some mineral and crystal mining in this area and some farming but the topsoil is thinner. There is also coal in this area (of course it is on above the gneiss) and pine forests. The Appalachian mountains have been the source of gold mines, marble quarries, and some gem stone production. There are also copper mines. In the north west corner of Georgia is the valley and ridge provence. It runs up the western side of the mountains and consists of deep valleys and steep ridges running north-south. These are the eroded remnants of the folded land behind the Appalachian orogeny (mountain building event). This region is most notable in restricting east-west travel while generally making north-south travel easier by river.

The point of this rambling is this. Certain minerals, metals, gems or whatever, need a specific environment in which to form. But the transportation mechanism of these resources may play a more important role in where they are found. For example, gold is most often discovered in rivers first, but that is obviously not where it formed. Other resources, like marble, must by found where they formed. Once marble erodes it is no longer marble. Water is the most important transportation vehicle. liquid water can carry solid or dissolved materials great distances. Once the water slows or evaporates it can drop it's load. With a hydrothermal vent, super heated water can carry a variety of minerals from deep in the earth and deposit them on the surface by deposition. Frozen water in the form of glaciers can move vast amounts of material long distances. For example of diamonds from Canada being found in Wisconsin. They also scour the surface and can expose hidden veins of minerals that may have otherwise gone unnoticed.