Personally, I don't see a huge problem with grain here(and I'm very nitpicky!). To me it seems like part of the cyrstals. I do agree that added contrast would add depth to the image but I wouldn't add a lot. Maybe add a sharpness filter, but that would add to any existing noise. Now what I like. I really like the purplish-blue hue the crystals have, as well as the lighting. Not too dark nor too bright.
From a jewelers point of view, these crystals are lovely.. I would have no problem turning them into a lovely peice of jewelry.. I don't see the graininess. I am well aquainted with crystal and how it looks.. It is a good clear shot of a beautiful blue crystal.. This looks to be the true color of the crystal and not computer enhanced.. Very good and a 10 from me..