When you look at the massive amounts of rock minerals sold to unwary customers at the retail level, it is obvious that a lot of people believe in the "a mineral is a mineral is a mineral" theory. What people fail to understand that limestone may be primarily calcium, but the molecules are so large the body cannot assimilate it at a cellular level. The tiny amount that is broken down in the body is not enough to provide the required amount for optimum health. However, a big serving of Collard Greens or broccoli will supply plenty of usable calcium. A banana will give you potassium and citrus fruit will let you have a good supply of natural sodium. What could be easier?