A Diamond in the MIND

Hello Katy,
This has been bugging me for sometime. When I first heard the title song for the lastest album I understood about a diamond in a mine,which made perfect sense grammatically speaking. However, in time after viewing the lyrics and of course the latest live release "Diamond in the Mind", I became quite confused. I thought perhaps possibly the word could be spelled either way, but the dictionary offers the following...
mine (n.)- a hole in the ground for extracting minerals or ores. (as in a diamond)

mind (n.)- the center of consciousness that generates thoughts, feelings, ideas, and perceptions, and stores knowledge and memories.

Please...please tell me now, I am missing something?
Many thanks and best wishes to the guys for their Olympic moment up and coming soon.

Dear Howie,
It's "a diamond in the mind" for three reasons.

Firstly, in The Rolling Stones' (note the use of the apostrophe and the absence of the normally following "s". The case of the plural possessive is the only case in the English language when this is correct in terms of punctuation. Alternatively, I could have correctly referred to "Jagger and Richards's song", but in given the opportunity to name check the greater entity, i.e. the band, I didn't. Put simply, anything else ain't English, and if it ain't English, it's Greek to me.) song "You Got The Silver", Keith Richards sings "you got the diamonds from the mine". As much as I love that song, I did not want to put myself, and by implication Duran Duran, in the sights of any accusers of plagiary.

Secondly, I am attracted to the metaphor of a thought so pure and crystallized that it actually becomes a psychic jewel, one that also sounds like something which is (and by the way Howie, there is nothing grammatically incorrect about "a diamond in the mind") much more rational and expected, i.e. "a diamond in the mine".