I watched a CG Masters tutorial about PBR (https://youtu.be/cvu5XYrZT6Q). In this video he gives a link to IOR table of commonly used materials (https://pixelandpoly.com/ior.html) and values in it can be used to calculate the specular value for the material. For example, asphalt has IOR of 1.635 which gives us about 0.73 of specular. And it looks pretty good especially with bump:
But there's no values in the table for such materials as paper, concrete or stone, which I found really strange because asphalt was here. I searched for the rock/stone values and found one: 11.07168, which gives 8.701 of Specular.
How do I make a PBR stone wall material? Could you please provide some links to Youtube tutorials? I've tried to search. For example Blender Guru always uses textures from Poliigon with normal maps, albedo, etc. But I want to achieve this procedurally.
P.S. By the way, I've just learnt that what we call an asphalt is technically an asphalt concrete. The real asphalt is a viscous liquid (https://en.wikipedia.org/wiki/Asphalt). And it confuses me more: if the table provides value for the liquid Asphalt, why does it look good in the first screenshot? And if this value is for asphalt concrete why is it provided here and the value for stone is not?