7.5 - Here goes a full comment: Choice of colours is coherent (st of warm colours). Attention to details is nice, and shading technique is ok. As for the NMM: the trick for NMM is to represent light reflection with a blending, going to pure white spots. This pure white is what makes the shining. Even in the dark, metal shines. Try doing the same as you did with the gems. The gold is also closer to that concept. (and yeah, I don't have anything in my gallery for reference. but it'll come someday soon.)
Regards - Sylvain