Black glitches when rendering

Ok…this is probably incredibly obvious and likely asked a million times, but I couldn’t find it anywhere… :frowning: I just started out and tried to make an eyeball, but when looked at the rendered version I got this:

I don’t have the tiniest idea what I did wrong, so I can’t give much more information i fear, except maybe that I tried to follow this tutorial: https://www.youtube.com/watch?v=Rap0re85QSA

Hi Galanthor,

Provide your file so somebody could investigate the issue.

Most likely duplicate areas,
but we still need the .blend file.
go edit mode:
-remove doubles. “maybe” this resolve the problem
-cheers