Gemstone refraction and reflection

Discussion
1

I would like to show ring with gemstone inside three.js. Is it possible to get f.e. diamond refraction and reflection like here: link. I would like to get gold (PBR) roughness + metalness + normal map and diamond with only refraction shader (hard cut).

How to do it from scratch or how to convert that shader from link to three.js?

2

Have you seen the WebGL / Material / Reflectivity example? With a more faceted model like the one in your example it looks like it would give a similar effect.