For the last few years Anton Palmqvist has been diligently creating a useful website where CG artists can go to look up the physical properties of most materials we are likely to need. Nice to have an alternative to the rather chaotically laid-out refractiveindex.info.
https://physicallybased.info/
Very clear layouts, complex IOR values, typical color and even density values.
Also relevant values for lights and cameras, and some useful tools for converting Specular to IoR and sRGB to Linear.
CBR