Elemental Truth

Something a little different from me this time. 

I've often wondered about elementals, What's an earth elemental made from? Would a sand elemental be different from a compost elemental, or are they just both earth elementals? I decided to create a charater who could do some experiments to find out exactly what's going on. Her name is Elkeelia Bracebridge, and she's a retired summoner with time, and wealth, on her hands. What's a fine lady to do with her spare time but create elementals in the cellar and see what happens?