CHALYBEATE is a 10 letter word that starts with C.

1. \Cha*lyb"e*ate\, a. [NL. chalybeatus, fr.
   chalube["i]us. See {Chalubean}.]
   Impregnated with salts of iron; having a taste like iron; as,
   chalybeate springs.
   
   

2. \Cha*lyb"e*ate\, n.
   Any water, liquid, or medicine, into which iron enters as an
   ingredient.