Preface: I've worked at a major jewelry and gemstone retailer, specifically in product imaging.
We exclusively use macros for all gemstone shots and usually use macros for all other purposes, occasionally using the TS-90 for necklaces and similarly large pieces. Irrespective of maximum magnification, longer focal length lenses are preferable for their increases in working distances (primarily for video, however) for usability with our Ortery boxes and other light cages. Depending on the piece, we either use glass, felt, or matte white bases if it is for a particular photo shoot. However, the majority of our product (just for the online shots and stuff) simply has the white background photoshopped out. No matter how clean your background is, you will see dirt and other distractions.
Obviously, the macro lens would be the best choice by far. But a standard lens with a closeup lens (or mounted backwards or using extension tubes) can definitely suffice. As most people have said, lighting is the biggest key. Reducing washed out specular effects, while maximizing the refraction in facets, is quite difficult. Also, you will see everything in the entire room in reflections, so a dome is pretty ideal as well.
Hope you enjoy photographing jewelry!