geodes are among the most interesting rocks you can find.
these rough stones are quite light in weight because they are nearly hollow.
Geodes were once round or egg-shaped holes in clay or limestone in which water collected.
layer after layer was formed as ages went by.Minerals in water hardened into a thin shell round the hole.
its center was lined with lovely gemlike crystals.
in time the clay or limestone round the geode was washed away.
A hard , hollow mineral rock was left.