Onslow speaks it correctly, in my opinion.  The better prosumer(non DSLR) cams will do a good job with proper set-up and imaging skill.   Some of the fantastic and fine macros on 'rosity are taken with such cameras.  

If you don't find images doing as you want...there is always the option of farming out the photography.  Unfortunately, many pro photographers are nearly as lost in doing jewelry photos as anyone else.    Those who do stuff like eBay shots for a fee might be an option..all depends on where and how the images will be used.

Magazine shots will often use multiple images followed image software to bring the final images to readiness.     That is about the sum of my knowledge at this point. : )