Board Thread:General Discussion/@comment-25317362-20140925205832/@comment-26812261-20140926025021

She has a gem located her back which confirms she is a Crystal Gem, she probably just said Crystal in a way like that to Steven and others to intimidate them. After all she is EXTREMELY powerful.

The gem proves that she's a gem, but what I'm saying is that "Crystal Gem" isn't the name of their species, but rather what GAP and Steven refer to themselves as. In other words, all Crystal Gems are gems, but not all gems are Crystal Gems. I can't see any other reason for them to have kept making the distinction in these episodes.