Lump of coal bug

[gubu]

Hi,

So I've picked up the lump of coal numerous times, however, it won't unlock on my collections page? It's annoying because I'm stuck at 96% and cannot get platinum/golden god and get 100%... Grr... is there any way to fix this?

[cenho09]

Okay, so a couple of things READ ALL:
1. There are hidden achievements, unlocking the lump of coal won't unlock the last 4% (Eve's Bird Foot, ???'s Soul, Samsons Lock, Maggy's Faith, Isaac's Head, Cain's Eye, and Judas' Tongue, not sure which are hidden and which aren't, but they're all achievements)
2. If you're on a mac, steam achievements are a bit buggy, there's a way to fix them.
3. You need all BUT the lump of coal to achieve platinum god, it is the SINGLE, ONLY item/achievement? you do not need.

Long story short, you don't need lump of coal

source: http://bindingofisaac.wikia.com/wiki/Achievements