I'm ignorant of the formal nomenclature of cat fancying, and I can't be bothered to edumacate myself via Google just now. So: I don't know if "grain" is a term of art for fine feline fur, but these images certainly highlight the lovely fine grain of each's coat. George's coat is like a veneer of exotic wood; Heidi's has a moiré luminosity, like watered silk.
Loverly!
If I think of it, I'll check my perceptions again when I'm sober.