For shiny objects, use “tent” lighting. Construct a tent using a white bed sheet. Stretch the cloth so that it is taunt, causing it to hover over the object to be photographed. If hot continuous lights are to be used, consider purchasing a white window curtain made of fireproof fiberglass. Once the tent is constructed, you light the object by aiming lamps at the tent, from above. The object is to create highly diffused lighting. By highly diffused, I mean, light that has no apparent direction. The camera peers at the object via a hole cut in the tent.
For small objects, like gemstones, you can create an integrating chamber using white foam board or Styrofoam packing material. Again, you make a chamber and illuminate via holes cut into the walls of the chamber. The lamps are directed so they play on the opposite wall. The idea is, the light reverberates about, so it arrives to illuminate the object with no discernable direction.
Some other tricks use a dulling spray. This is a matte lacquer spray paint or hair spray. You can make a dulling spray mixing water and talcum power. This mixture is sprayed on the object with an atomizing spray like the type used to apply perfume. The spray’s job is to mitigate reflections. If gemstones are the object, they can tolerate matte lacquer. The lacquer is later removed with an appropriate solvent.