The example you show of ear rings are they not just crystal cut like a
diamond and as the facets catch the light and bend, it this breaks the light spectrum giving a rainbow effect , just like a real rainbow after a shower of rain.
Just another thought there is a glass called Rainbow glass, this is made in WV I have a photo of a small jug with label I will look for it and post a link.
I may be way off track here with both of my comments!!
PS. Hope I will be forgiven for an off topic note, is there any chance of some photos of your light table ( if I have the right Nancy )
Tony H in NZ
I have added two photos in a new album Rainbow Glass.
Tony H in NZ.