The song debuted on Z100 in New York this morning. If you hadn't seen it yet, the cover for the single has her rolling a joint made of diamonds. Well, hopefully that's diamonds and not some other kind of rock.
Rihanna posted the lyrics to "Diamonds" as a .pdf file on her site, so you can be sure she is in fact singing "we are diamonds in the sky" and not "weird eye mounds in this guy."