We have some Halogen MR16's at 6500K good for diamonds and crystals, not good for gold, and LED MR16's at 5700K. Both high end products from Ushio of America, the same company that does the Luxor pyramid lighting that you can see form space.

If it's a certain spectrum that you're looking to achieve then that's the pro's and con's of the various light sources and why you would not look to replace one for the other. We sold the Axiom High Powered LED modules to a Theme Display Company that builds for PPG Paint recently for the purposes of display cases to show off their paint accurately.