Susan Hundley, age 11, of Charleston, West Virginia, for her question:

How were the minerals formed?

There are thousands of different minerals in the earth and their stories go back to the very beginning of the world. Scientists tell us that the earth was once a gaseous ball and, of course, its gases were composed of various atoms. As it became a solid world, its different atoms took different forms. At a certain temperature, all the separate atoms of gold became solid metal. At another temperature, atoms of hydrogen and oxygen united to form molecules of liquid water. Each mineral becomes solid or liquid at its own special temperature. And as the solid earth took form, its assorted minerals settled one by one.

Meantime they are seething upheavals below the ground. Mixtures of assorted minerals were melted to the molten state. More atoms and molecules mixed and combined.

As the molten lava cooled, they formed hundreds of different minerals such as silica. Many earthy materials were dissolved in sea water and settled to the bottom. Some of them dried out again and formed layers of more assorted minerals. Every mineral has its own long and eventful tale to tell and almost every rock has a story of its own.