Certain forms of magnesium, such as magnesium oxide or sulfate ... If you see blood in your stool or notice black, tarry stools after taking magnesium, stop taking the supplement and talk to ...

The iron oxide is no longer a pure metal, it is a dull, dark-coloured, metal compound. When you burn magnesium in the air in the same way that the iron did, the magnesium reacts with oxygen to ...