For those who want to know a bit more about FairPhone and specifically how they address cobalt mining.
They have a pretty good video and a blogpost about the sourcing of cobalt.
Blogpost: https://www.fairphone.com/2013/03/14/a-fair-price-for-cobalt...
Video: https://www.youtube.com/watch?v=WWVFXesVScA
Full disclosure: I once worked on a part of FairPhone's webshop.