Why do people call Mary Magdalene the "Black Madonna"?

Today I heard something most peculiar, and was wondering if there is a Biblical basis and/or if there were other denominations that teach this. An older gentleman whom I know very well, and almost think of as a father, during a discussion about Mary Magdalene said (verbatim): > Oh, well you see - some call her the "Black Madonna." (Because we had talked about theories as to whether her and Jesus *could have* been married - though this is irrelevant to the question at hand) This is a most perplexing "revelation" to me, knowing that Biblically we know that Mary was saved from a life of sin to serve Jesus Christ. I've looked all over the internet, and the most I can find about anything "Black Madonna" related is depictions of Mary, Mother of Jesus as a black woman. What is the basis for this teaching? Is there any Biblical basis it? What groups teach it today?