I did a test in Thea Render with @DavidRutten 's “Crystal Maker” Grasshopper tool:
I used a tiny 0.01 Edge Softening for some subtle edge-highlights and all the materials are lab-measured gems using .ior files for diamond (most of the gems in the background), ruby, sapphire, amethyst, aquamarine, emerald, tourmaline and titanium dioxide (lower right). (Some of the colours are quite subtle in this size of just a few millimetres…)
The only light is from a HDRI, so the caustics are not as defined as usual with Thea.
IOR file based materials can’t be rendered yet with the GPU kernel of Thea, so I rendered this overnight with the “TR2” kernel, which is fully unbiased but CPU-based.
With TR1 & TR2, Thea computes even the correct chromatic aberration for these kinds of materials since the .IORs are per-wavelength.
Slight post in Lightroom.