Sapphire Blue - G. Doucette

He squirted water into both glasses.  The clear ouzo turned milky white and perfectly opaque instantly.

 

Mara let out a gasp. "Magic," she said.

 

"Chemistry.  Although it's sometimes not easy to tell the difference."

 

Mara is supposed to be a highly intelligent woman.  Up until this point in her life she has had no reason (that we know of) to believe in magic or the supernatural.  In fact, I'm pretty sure you need some amount of science for an advanced degree in archeology if you do anything relating to dating, cleaning, preserving, etc of artifacts - and there are some pretty amazing chemical reactions in science.  Even just high school level science.