Are athames a certain type of knife?

or can you just pick a dagger and call it an athame?
and if you can what type of metal should they be made out of?
Update: it is a word but i don't know if the englsh language recognizes it as a word.
google it and you will get lnks to athames and other things. but i can't find anything that says what type of metal and I'm not awake enough to read her whole answer yet XD
7 answers 7