Zechstein seabed in northern Europe. This seabed lies 1,600 to 2,000 meters beneath the surface of the earth, where it has been protected for 250 million years. The ultra pure oil thereby provides high levels of magnesium and trace elements from pure, unpolluted deposits found in this ancient sea. Always look at the source of your supplements.
Because it is not man made it is free from heavy metals and the only thing you will find in the bottle is magnesium chloride and other naturally occurring trace minerals.