Hi Terry, Try going for a colour Temp of around 4300k-5500k keeping in mind there is such a thing as too much light volume. Thats what Ive found for Australian Opal but nothing beats sunlight.
Im currently trialing different combinations of 4300k and 6500k led fluro battens diffused with their own light covering followed by the light box material before the Stones when I photograph. You can also try Diffusing with UV Filters if theyre still used now things are digital.
I actually found my Galaxy S5 Took better photos than my Entry level Nikon DSLR did in the way of capturing colour in Australian Opal. Maybe give that a shot - I havent done too much with Welo really. I bought some lovely rough about a year ago but found it very unstable which resulted in it going in the garden with all my other discards (My 4yr old son loves fossicking out the back hahaha) although I did keep a little 1.0ct Trilliant Cut thats still in the cupboard that is gorgeous when you hydrate it!!