Jewelry can be one of the most difficult subjects to shoot because you are shooting small subjects which are generally very reflective and hard to light. You may want to look for a book or a website on specific techniques on this type of shooting as many pros spend a lifetime perfecting the techniques, and there is more information than can be covered in a short article.
However, a Micro-Nikkor lens (or more generally a "macro" lens) is a special lens designed to take very sharp images at very close focus distances. Nikon offer several different options here:
Each of the Micro-Nikkor allow the same 1:1 reproduction size but the longer focal lengths (i.e.105mm) allow you to be farther away, making it easier to properly light the subject. Other tips:
1) Use a sturdy tripod to hold the camera still.
2) Use small apertures (i.e. f22) to increase depth-of-field (zone of sharp focus) so that the entire subject is in focus.
3) "Tent" style lighting where the lights are outside a sheer fabric "tent" of diffusion material can reduce shadows/ reflections. Shoot through a hole in the tent.
4) Reflector cards can also be used to control the light.