Few days ago there was a bug found in TFC b79.14 (at least): graphite only spawns in schist. I.e. it stopped spawning in marble, gneiss and quartzite. It will be fixed in .15:
http://terrafirmacraft.com/f/topic/7...wns-in-schist/

It's not clear if the issue appeared exactly in .14. I have asked there about the exact build this issue was introduced.

So let's see what the answer will be, and if it's bad, e.g. the issue appeared in b79.1 - that means the pre-generated world is affected - then let's discuss how we can improve the situation with much less graphite available in comparison with b78. Or maybe there's no problem at all, I don't know TFC guts too well.