I came across a site that offered a whole library full of different high-quality materials (a ton of them) - a paid one. however, I can’t remember what the library is called, I don’t suppose anyone here knows of the one I’m speaking of?
Was it Poliigon?
No, I believe it was made specifically for blender
Cycles material vault.
I could swear the website looked different, alot more appealing. although it does appear to have the materials I remember, so cheers! 
edit: saw that you could scroll down on the frontpage, it’s definently this one. thanks a bunch
Hum you can also find paid-material (and other stuff) on Blender Market.
Chocofur have a great material library too, and their shaders are free.
I did not know CMV, thanks!