Probably the charcoal tablets. Because it doesn't always happen the first time you take a few, and sometimes it can be the timing of you taking the charcoal tablets and then it going through and into your bowel at just the right time to where your bowel motions will come out dark.

I wouldn't be too worried about it. Also, once the last amalgam has been removed, the body can sometimes start to go into detox mode and people can have this occur pretty quickly or months later down the track. So your body might actually be offloading a bit of mercury already!

The black stools could be the charcoal or could be some detoxing starting up.