Gold and silver tiles

Lynette

I've been so busy having fun and playing the game that I have not noticed how the gold and silver tiles are formed.Are they random, or have they been generated by gameplay (and if so, how)?

Gen_V

The FAQ says the gold tiles double your points if you use them.  I don't know about the others.

Lynette

I know that gold tiles double your word score and silver tiles your letter score, but want to know where the gold and silver tiles come from?--- I think may be it is from a certain number of letters in a word...or are they just random?